Author Topic: dubcats secret little hideout  (Read 93021 times)

2016-10-10, 14:35:11

dubcat

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This will be my little hideout where I share crazy stuff and what not.

I will make a proper first post later.
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2016-10-10, 14:35:24
Reply #1

dubcat

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During the Corona 1.5 Daily Build phase I was pushing/testing hard to get all the proper Blending Modes into CoronaMix.
There are three main reason for this. I will be posting two new mini guides on two of the reasons in the near future.
The third reason is procedural masking.

I've been talking to Ondra about procedural maps/masks for a couple of weeks now.
My idea is to turn Corona into a crazy ass procedural beast.

Last night I put together a proof of concept inside the material editor. It's basically Quixels dDO inside max.
Right now I'm using baked maps for Curvature, AO, ObjectSpaceNormal and Gradient. Everything else is done inside the material editor.
I've posted Mantis requests for Curvature, ObjectSpaceNormal and Gradient maps. If we ever get these maps, we only have to swap them with the baked bitmaps, and there we go.
Crazy ass mask generator inside max!

Here are the input maps.



My proof of concept mask generator that behaves like Quixels dDO.



Out comes



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2016-10-10, 15:17:14
Reply #2

Dionysios.TS

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oh God....
Responsable d'Imagerie
Renzo Piano Building Workshop / Paris

https://dionysios.myportfolio.com/

2016-10-10, 15:20:34
Reply #3

romullus

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That's crazy. Nice, but crazy :] Wonder how big penalty in render time you'd get from such material setup compare it to baked maps?

Doesn't CoronaData map already has world object space normal map pass? Can't test it at the moment.

Anyway, i love procedural stuff. Insta subscribe!
« Last Edit: 2016-10-10, 22:02:24 by romullus »
I'm not Corona Team member. Everything i say, is my personal opinion only.

2016-10-10, 16:16:18
Reply #4

Ludvik Koutny

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Yep, I enjoy procedural shading too...

Aside from Romullus' question if there isn't already something you need in CoronaData map, the gradient map you mentioned, doesn't 3ds Max's gradient ramp already do that? I mean you can plug in source texture and map its luma range using that gradient.

What I am most missing for procedural shading inside 3ds Max is just a simple blur texture, that just simply blurs.

2016-10-10, 16:20:19
Reply #5

TomG

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Lol on the simple blur, I was looking for that last week but could find no way to do it (wanted to blur some procedural output), so yes, that would be a useful thing!

2016-10-10, 17:25:18
Reply #6

karnak

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I support this.
Consider that hero materials can be as complex as the one that dubcat posted, but for the rest of the materials I think just the curvature map can do wonders without too much penalization.
Corona Academy (May 2017)

2016-10-10, 19:20:38
Reply #7

dubcat

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One of the first things I did was to test all the CoronaData maps, the position map is not the kind we want.



Round Edge Map is almost a Curvature map. I use it as a filler curvature map every now and then, but it also masks crevices white.
I have reported this is my Curvature thread on Mantis.



The biggest problem right now is that all the default 3dsmax maps are calculating shit in linear and we need sRGB.
I'm adjusting all these maps afterwards with an Output map as a little hack.



These functions need to be added to CoronaOutput in Photoshop form. (Reported on Mantis)
- Invert
- Gamma
- Legacy Brightness
- Legacy Contrast

We also need to split the Curvature map into 7 parts, to get full control, and then blend them back with Overlay.
To do this we need Highpass filter (There are functions out there for real time) and Gaussian Blur.

I did a 32 pass test.
Big ass procedural tree = 06:45 min
1 compiled bitmap = 01:40 min

I hope all this stuff can be bundled into one optimized map. I've already offered to make a reference sheet on how all this fits together.
If Team Corona want to tackle this map, just text me on Skype.

I made this mock up (v0.1) last night when I made the proof of concept.
It might look overwhelming, but when you load the map, all the boxes should be closed.
So if you want to work on Curvature, you open the curvature section etc.
I forgot to add master opacity for each map.

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2016-10-10, 20:50:52
Reply #8

steyin

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I used to think that procedural maps did not tile for some reason and instead went on in random generation forever. Kind of wish they behaved like that instead.

2016-10-10, 21:03:41
Reply #9

pokoy

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I have to say I'm glad some people here fall into the mad professor category - in a good way, of course - I'm awestruck, looking forward to where this could get one day.

2016-10-10, 21:27:33
Reply #10

lacilaci

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Well if this is not something "in the works" now, it could be listed at least for now in "the most wanted features" poll...

Flexible procedural map even partialy substituting the likes of substance or quixel mask generators is a great added value.

2016-10-10, 21:56:50
Reply #11

karnak

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How the shader graph would look like with this CoronaMaskBuilder compared to the image you posted at the beginning?
Corona Academy (May 2017)

2016-10-10, 22:03:34
Reply #12

romullus

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Doesn't CoronaData map already has world object space normal map pass?

One of the first things I did was to test all the CoronaData maps, the position map is not the kind we want.

I mean this:

I'm not Corona Team member. Everything i say, is my personal opinion only.

2016-10-11, 23:15:56
Reply #13

dubcat

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I've remade the FuzzyShading map from Unreal 4.

It's using the default Unreal 4 settings, including falloffs.
There are 3 parameters you can adjust to taste. These are Core Darkness, Edge Brightness, Power.
You can either use it as in the example below, or you can make one material for the stone and one for the moss. And then blend them together with the fuzz mask.

Download link bellow.



I used one of the free Megascans assets to test the shader while I was building it.
I can't wait to try this shader on fabrics!

Here are some test renders, in case you don't know what all the fuzz is about. (I used the default settings).
Open the pictures in a new tab for maximum comparison satisfaction!

Normal Corona Shader



FuzzyShading Shader



Enjoy.

How the shader graph would look like with this CoronaMaskBuilder compared to the image you posted at the beginning?
The graph and the mock up is the same :)

I mean this
It looked kinda similar, but the hotspots and falloffs didn't quite match. If this is the correct map, it needs to be adjusted a little.
« Last Edit: 2016-10-13, 00:26:50 by dubcat »
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2016-10-12, 09:57:36
Reply #14

romullus

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I like how it kinda glows on grazing angles and in shaded areas, but transition from rock to moss doesn't look that good.

It looked kinda similar, but the hotspots and falloffs didn't quite match. If this is the correct map, it needs to be adjusted a little.

Not sure about that, but could it be due to difference in how normals are calculated in various apps? Sadly there isn't unified standart for normal shading.
I'm not Corona Team member. Everything i say, is my personal opinion only.

2016-10-12, 19:01:20
Reply #15

dubcat

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I've ported Metallic Shading from Unreal 4.
The falloff has bright edges, dark middle and semi bright center.
In Unreal 4 you are only allowed to change the Base Color, but you can tweak the gamma inside the Pow maps for different looks.

Basic shader to show the effect





I've also updated the Fuz shader.
- Fixed some math in the Core Darkness section.
- I realized that pow is the same as inverse gamma, so now you can adjust Power the same way as in Unreal 4.



Transition from rock to moss doesn't look that good.

This has to do with Edge Brightness, I had it at 1 during testing.
« Last Edit: 2016-10-13, 18:49:19 by dubcat »
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2016-10-15, 09:13:20
Reply #16

rambambulli

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Professor Dubcat,I love it! I have been looking for this to hook the curvature, positionmaps, etc. to some Substances I made.

2017-02-03, 19:47:27
Reply #17

dubcat

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Megascans Studio heightmap based blending inside 3dsMax





edit:
The Gamma 2.2 map is there because Output Map is linear, and we want to emulate Levels in Photoshop.
« Last Edit: 2017-02-03, 22:56:12 by dubcat »
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2017-02-16, 00:04:10
Reply #18

dubcat

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Edit: Bug in my auto script, will post update when it's sorted out.
« Last Edit: 2017-02-16, 21:56:38 by dubcat »
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2017-02-16, 15:10:01
Reply #19

romullus

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I thought that after most recent changes in Corona material (PBR mode), its glosiness matches 1:1 with Vray GGX, isn't? :/
I'm not Corona Team member. Everything i say, is my personal opinion only.

2017-02-18, 02:41:13
Reply #20

dubcat

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I thought that after most recent changes in Corona material (PBR mode), its glosiness matches 1:1 with Vray GGX, isn't? :/

It should be closer, I noticed a bug in my vray script. The fstorm table is accurate. I'll wait until the table is 100% complete before I post it again.

------------------------------------------------------------

Here is a little "how to get that fStorm look in Corona" post.

I've attached a little Photoshop script that will turn your harsh Corona renders into soft fStorm renders.
This blur/sharpen effect really help sell that photorealism, when did you capture a picture with your camera and the noise was pixel perfect ? (I'm not talking about ISO 1million)

If you are using Arion to add chromatic aberration, you will already have a blur like this (- the sharpen), since this is a side effect of the R G B transform. But this Photoshop script is shifting R G B equally.
If you do an anti chromatic aberration operation in CameraRaw after Arion, you will see that your render still looks more Photorealistic after the anti chromatic aberration operation. This is because the blur that is the main ingredient.

This stuff should be included in Corona frame buffer. Go and +1 on mantis!



and this is how you can emulate fStorms "Angle Affect" option in Corona



In fStorm the "Angle Affect" parameter goes from 0-1. After some quick testing, this looks to be the same as IOR 1.5 - 3
I've made a little improvement to the effect. You can specify a value that gets multiplied with the base glossiness. This is nice for rough materials, where you don't want the edges to be 255 glossiness.
So tweak IOR and the multiply value to taste.

This feature should be included in Corona if you ask me! I notice this effect each time I lay down, even on rough fabrics.
Next time you lie down in bed or drunk on the floor, try to look for this effect, and then go and +1 mantis!





I've also attached two LUTs that emulate the default 0.3 contrast in fStorm and a 0.15 contrast version. The contrast slider in fStorm don't affect white, so it's more of a black crusher. The effect can be really strong, so you might want to tone it down.
This is 0.15 contrast



-1 HC in fStorm that has kinda become the standard, is 50 hc in Corona!

fStorm is caped at around 0.40 Corona glossiness. Which is a bad thing, but now you know.

Another thing that Corona is still missing that both fStorm and Vray has, is focus pick in frame buffer. +1 mantis if you are missing this feature!
You won't believe how amazing it is to build your scene. Walk around as a photographer, focus pick in frame buffer. CTRL + C, render afterwards. This is a MUST feature.

fStorm renders object with no material as default material, instead of random object color.

So there you go, if you follow these guidelines you will get that cRona look!

Don't forget to Mantis, shit won't happen if you don't act! Spread the words to your friends.
« Last Edit: 2017-03-11, 03:22:26 by dubcat »
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2017-03-25, 02:52:35
Reply #21

dubcat

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edit:
These LUTs ship with Corona 1.6

I've been dumping cameras as LUTs for the past 6 months or so.
Here are 3 of those dumps.
Think of your renders as "linear raw" files from your camera, these LUTs do the camera processing (what your JPGs looks like in camera).
(By "linear raw" I mean (dcraw.exe -v -w -H 0 -o 1 -q 3 -4 -T), not CameraRAW/Lightroom import!)

You don't have to use them at 1 opacity. If you apply "Photographic 01" with 0.68 opacity, it mimics another camera. So feel free to experiment.

With these LUTs you can use 30 sRGB black / 210 sRGB  white in your materials, and they will look nice and contrasty in your final render.

These LUTs make your linear render look like a processed camera photo, it's up to you if you want to take it any further in CameraRAW/Lightroom. I always end up doing some kind of local processing in CameraRaw.

I want to give Juraj Talcik and Peter Guthrie credit for giving me valuable feedback while I dump these cameras (and still do). So thank you super duper mega very much!

Here are some quick test renders to show the general behavior
As you can see, they all have the same kind of contrast, but the HSL adjustments differs a lot.









What LUT is your favorite ? Did it improve your render ? Let me know ! (If you find weird color shift problems or anything like that, contact me).

edit:
Here are the render settings. These Sharpening/Blurring settings will give you that nice fStorm noise.



edit:
Attached EV normalized versions so you don't have to reduce EV.
« Last Edit: 2017-04-06, 21:09:19 by dubcat »
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2017-03-25, 10:39:38
Reply #22

pokoy

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This looks good! Will try next week - thanks for sharing them!

2017-04-01, 21:22:11
Reply #23

Correntes

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yeah i will test it too.

will see how it compares with exact reference photo

2017-04-01, 21:29:25
Reply #24

olotl

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this is a really nice thread! lut's working great - thanks a lot.

2017-04-02, 13:36:26
Reply #25

miaz3

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@dubcat :

I find it strange to use LUT that is not related to the digital depth of the image rendered ?!
If I open the LUT there is only 32,768 correction line (2 ^ 15). But if you work on a 16bit image it would take 65,536 (2 ^ 16) lines of corrections ...
So why lost the half data ?


2017-04-02, 16:39:54
Reply #26

sebastian___

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Great thread. What cameras are used for the extracted LUT ?

2017-04-03, 11:18:27
Reply #27

Ondra

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@dubcat :

I find it strange to use LUT that is not related to the digital depth of the image rendered ?!
If I open the LUT there is only 32,768 correction line (2 ^ 15). But if you work on a 16bit image it would take 65,536 (2 ^ 16) lines of corrections ...
So why lost the half data ?
you are not actually losing anything, this is resolution of the mapping function, not the input data - even low-res mapping function can be used to transform high-res input data with no quality loss.

As an example: Corona VFB uses 32bit color format. If you change exposure, you are applying a transformation that could be expressed as 1 line LUT. But the output image does not lose any information

Rendering is magic.
Private scene uploader | How to get minidumps for crashed/frozen 3ds Max | Sorry for short replies, brief responses = more time to develop Corona ;)

2017-04-03, 11:22:20
Reply #28

Correntes

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Dubcat:

I prefer your PhotographicCurve v2  lut that you previously shared with albedos white 240  black 50 srgb corona contrast 4

30black/210white plus the luts seems to dark/contrasty and washout textures.

With the PhotographicCurve v2 setup i get an almost perfect material editor preview match up with the actually rendered.
Maybe I'm doing something wrong but this setup is a lot more predictable

2017-04-03, 12:17:34
Reply #29

nkilar

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Dubcat:

I prefer your PhotographicCurve v2  lut that you previously shared with albedos white 240  black 50 srgb corona contrast 4

30black/210white plus the luts seems to dark/contrasty and washout textures.

With the PhotographicCurve v2 setup i get an almost perfect material editor preview match up with the actually rendered.
Maybe I'm doing something wrong but this setup is a lot more predictable

With white color at 240 I presume the render times have fallen of the charts (super high), right?

2017-04-03, 12:51:57
Reply #30

miaz3

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@dubcat :

I find it strange to use LUT that is not related to the digital depth of the image rendered ?!
If I open the LUT there is only 32,768 correction line (2 ^ 15). But if you work on a 16bit image it would take 65,536 (2 ^ 16) lines of corrections ...
So why lost the half data ?
you are not actually losing anything, this is resolution of the mapping function, not the input data - even low-res mapping function can be used to transform high-res input data with no quality loss.

As an example: Corona VFB uses 32bit color format. If you change exposure, you are applying a transformation that could be expressed as 1 line LUT. But the output image does not lose any information

I meant, losing half data of bit depth of the LUT, not the raw. This LUT is just like a "film look" ?!
Is not totaly matching to the raw data (eg 16 bit or 32 bit) soulder and foot curves too.
Which causes either the floor noise will be processed, or the high values will not be processed by the curve. (And vice versa).


2017-04-03, 13:33:07
Reply #31

Correntes

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[/quote]

With white color at 240 I presume the render times have fallen of the charts (super high), right?
[/quote]

a little bit yeah :S

i'm still testing

2017-04-03, 21:47:45
Reply #32

nkilar

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With white color at 240 I presume the render times have fallen of the charts (super high), right?
[/quote]

a little bit yeah :S

i'm still testing
[/quote]

Well if the contrast is bothering you that much maybe playing around with the filmic settings could do the trick. Then again it might not :)

2017-04-03, 22:32:20
Reply #33

ASaarnak

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Thank you for sharing the LUTs :)

2017-04-04, 01:12:27
Reply #34

dubcat

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I find it strange to use LUT that is not related to the digital depth of the image rendered ?!
Maybe I'll release 64 sliced versions in the future, 41+ should be enough for what you want.

What cameras are used for the extracted LUT ?
I went into my Canon/Nikon folders and selected 3 random LUTs. I got a lot of Canon 60D LUTs in there, so one of them might be 60D.

Canon cameras have this magenta Tint to them, sometimes -10 green. This happens even if you calibrate the camera as perfect as you can. We need to use the sexy Tint feature in CameraRAW to get a perfect white balance. Since I'm dumping the real deal, I left this error in there. If you notice a slight magenta shift, it's a Canon LUT 99%.

Canons best friend.



and a big thanks to everyone else that has responded!
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2017-04-04, 11:23:47
Reply #35

Correntes

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Update:

I got it working and quite like the results

The 01b is the version with the luts and 210w 34b sRGB

2017-04-04, 11:55:35
Reply #36

Rhodesy

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Looks cool. When you say 34b is that 34 the lowest/darkest you set a black material or have I misunderstood? I assume the 210 is the white wall level?

2017-04-04, 12:00:13
Reply #37

Correntes

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yes

max white 210 sRGB
max black  34   sRGB

2017-04-04, 13:13:02
Reply #38

Rhodesy

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Thanks. Good to know.

2017-04-04, 14:47:47
Reply #39

agentdark45

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Update:

I got it working and quite like the results

The 01b is the version with the luts and 210w 34b sRGB

Wow that's some difference. Are you able to post any of the post processing settings that you used in conjunction with the LUTs?
Vray who?

2017-04-04, 14:49:50
Reply #40

Ondra

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good news, the new LUTs are now bundled with Corona installer
Rendering is magic.
Private scene uploader | How to get minidumps for crashed/frozen 3ds Max | Sorry for short replies, brief responses = more time to develop Corona ;)

2017-04-04, 16:49:03
Reply #41

Correntes

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Update:

I got it working and quite like the results

The 01b is the version with the luts and 210w 34b sRGB

Wow that's some difference. Are you able to post any of the post processing settings that you used in conjunction with the LUTs?

That's the beauty of it, get the exposure right, highlight compress an then I just  applied the lut at 100%, vignette, chromatic aberration, tweaked the white balance and that's it.
I do the post outside of corona due our layer workflow .

good news, the new LUTs are now bundled with Corona installer

That's wonderful news Ondra



2017-04-04, 23:42:20
Reply #42

miaz3

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Quote
Maybe I'll release 64 sliced versions in the future, 41+ should be enough for what you want.
I don't understand ?!
You deliver a LUT that was generated from 3 random LUT Canon dslr ... There is nothing logical in it ?!
Canon LUT are created for mapping Canon sensors, like arri, red et cie...
So what do not tweak a curve and that it ?! (ed: i just plot your LUT_03).

So here we've got a LUT that not mapping the raw data ? i'm not talking about 32 bit float raw, but just for this exemple 16 bit is enough.

It's that simple.
I just want to understand the interest of mapping a LUT that does not match the RAW's digital depth. Like dslr, or camera manufacturer do.



2017-04-05, 00:27:31
Reply #43

dubcat

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When you take a picture with your dslr in jpg mode, the raw goes through ColorMatrix, ForwardMatrix, LookTable and ToneCurve. That's what these LUTs do.
These should be applied in a specific order, since we can only apply one LUT and not 4 LUTs after each other in order, we can't get 100% match, but it's damn close.

I always take a color checker reference picture. This way I can control if the linear raw + LUT will match the camera JPG.

Here is one of my older Canon control tests.

Linear RAW converted to sRGB.



JPG from Camera



RAW + LUT (When you use dcraw to make a proper linear raw, it does not denoise the picture, so you will see noise on some colors, like purple)



Hope that helps you understand whats going on with these LUTs :)
« Last Edit: 2017-04-05, 00:33:51 by dubcat »
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2017-04-05, 07:48:10
Reply #44

Hamburger

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THe LUT looks great for interiors, but with harsh sun + sky system it really is too much contrast and shadows are massively crushed. Does it work for anyone else?
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2017-04-05, 10:41:30
Reply #45

romullus

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Yes, Photographic 1 (i don't use other two) works great on many bright low contrast scenes, but are unusable on darker, more contrasty scenes, as it gives so massive contrast, that is impossible to tone down, but to reduce lut opacity to 0,2 - 0,4 at which point there's little sense to use lut at all. Also, quite often i find that it's very hard, nearly impossible to recover highlights when using dubcat's luts. It just leaves big flat dead areas with no details. But in scenes, where it works, it works just great.

By the way, when using these luts, more than ever i wish that Corona VFB would have some controls for midtones.

That is my highly unprofessional impressions.
I'm not Corona Team member. Everything i say, is my personal opinion only.

2017-04-05, 17:13:24
Reply #46

romullus

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Hey dubcat, is there a way to apply your luts in photoshop? I tried to load it through colour lookup adjustment layer and i get very different result than in Corona's VFB. Probably i'm doing something wrong here - i have little to none experience with such things.
I'm not Corona Team member. Everything i say, is my personal opinion only.

2017-04-05, 22:17:27
Reply #47

miaz3

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@dubCat :
Thats a basic dslr workflow. Like every photographer do.
Your LUT (From dcp or icc) mapped to your dslr sensor, with everything that goes with it (Dynamic range, bit depth, ect...).
And this LUT cannot be used on a C-300 or D500, even H6D-100C...even less 35mm cmos...
It can be taken for a generic LUT, but Dynamic range, bit depth, ect... cannot be mapped exactly.

So your lut can be mapped to a cg render, but not cover the entire dynamic range of cg render.
Your lut cover only 2^15, minimum raw cg render (16bit) is twice the level value. So like a say before, black or white value (in some cases) will be clipped.
Data level distribution, won't match either.

Anyways, nobody care about mapping lut.

2017-04-05, 22:36:33
Reply #48

Juraj Talcik

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Anyways, nobody care about mapping lut.

I don't see what is the issue ?

It's free post-production tool, no one is holding gun against head of anyone. Do you provide some better one ?
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2017-04-06, 01:09:21
Reply #49

Hamburger

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Hey dubcat, is there a way to apply your luts in photoshop?

You can apply it through the Color Lookup layer. It works really well if you make it 50%. It gives a super nice contrast to exterior and interior renders I've tested to.
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2017-04-06, 10:22:35
Reply #50

romullus

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Hey dubcat, is there a way to apply your luts in photoshop?

You can apply it through the Color Lookup layer. It works really well if you make it 50%. It gives a super nice contrast to exterior and interior renders I've tested to.

I tried to load it through colour lookup adjustment layer and i get very different result than in Corona's VFB.
I'm not Corona Team member. Everything i say, is my personal opinion only.

2017-04-06, 16:55:50
Reply #51

dubcat

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Hey dubcat, is there a way to apply your luts in photoshop?

If you're render is in in 32 bit, Photoshop will apply the LUT in linear.
Photoshop will also clip your render, so you are better off applying it in the new Corona app.
« Last Edit: 2017-04-06, 19:04:30 by dubcat »
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2017-04-06, 17:26:47
Reply #52

Marcus

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Hey dubcat.

Thanks for your work on these LUTs and thanks for sharing it!
I really appreciate you effort on research and sharing everything to the community.

Here is a quick test with ...01.cube
I just applied the lut in Corona Frame Buffer. Nothing more.
I like it and will experiment further with it.

Best,
Marcus

2017-04-06, 19:15:00
Reply #53

romullus

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If you're render is in in 32 bit, Photoshop will apply the LUT in linear.
Photoshop will also clip your render, so you are better off applying it in the new Corona app.

Yes, my render is 32 bit cessential render elements blended with linear dodge blend mode and on top of that is added colour lookup adjustment layer with your lut in normal blending mode, but result is very different than i get when apply the same lut in CVFB. Maybe i should have to change colour lookup layer's blending mode to linear dodge too?
I'm not Corona Team member. Everything i say, is my personal opinion only.

2017-04-06, 19:36:30
Reply #54

dubcat

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LUTs behave as sRGB in Corona, and Photoshop 32bit behave as linear.

Nice Marcus :)
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2017-04-06, 20:13:48
Reply #55

romullus

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Oh, i see, so there's no way to get exact match between those two?
I'm not Corona Team member. Everything i say, is my personal opinion only.

2017-04-06, 20:51:18
Reply #56

miaz3

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Anyways, nobody care about mapping lut.

I don't see what is the issue ?

It's free post-production tool, no one is holding gun against head of anyone. Do you provide some better one ?
I just provide additional information that would allow for better control.
To see where problems may arise, you can read my previous post.





2017-04-07, 09:52:19
Reply #57

JakubCech

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Angle Affect
This feature should be included in Corona if you ask me! I notice this effect each time I lay down, even on rough fabrics.
Next time you lie down in bed or drunk on the floor, try to look for this effect, and then go and +1 mantis!



This is a very important request. Almost all materials I do I input falloff to the ref glossiness map to mimic this behaviour. I think this could be default behaviour - I think 90% of materials work this way (visually). So +1 from me.

2017-04-12, 23:49:01
Reply #58

dubcat

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Oh, i see, so there's no way to get exact match between those two?

Totally forgot to reply, been busy with deadlines. I added a Linear version to the original post last Thursday, don't know if you noticed.
But remember that Photoshop will clip anything above 255 even if you are in 32bit, if you plan on doing adjustments after the LUT, you are better off applying it in Corona/Corona Image App.

edit:
Big thanks to JakubCech for the +1 :)
« Last Edit: 2017-04-14, 12:06:38 by dubcat »
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2017-04-13, 10:00:45
Reply #59

romullus

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I added a Linear version to the original post last Thursday, don't know if you noticed.

No, i didn't. Thanks for pointing that out, i will give it a test as soon as i will get a chance to do so. And big thanks for your effort in general!!!
I'm not Corona Team member. Everything i say, is my personal opinion only.

2017-05-03, 19:36:27
Reply #60

Fluss

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Angle Affect
This feature should be included in Corona if you ask me! I notice this effect each time I lay down, even on rough fabrics.
Next time you lie down in bed or drunk on the floor, try to look for this effect, and then go and +1 mantis!



This is a very important request. Almost all materials I do I input falloff to the ref glossiness map to mimic this behaviour. I think this could be default behaviour - I think 90% of materials work this way (visually). So +1 from me.

Well, Ondra almost promised it a long time ago. "AFAIK this is part of disney BRDF model, so it will be almost certainly included in Corona PBR mtl" -> https://corona-renderer.com/forum/index.php?topic=12621.0

2017-05-06, 06:45:10
Reply #61

worx

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Update:

I got it working and quite like the results

The 01b is the version with the luts and 210w 34b sRGB

Which lut was used for this? Also was it applied in max corona or in PS?
I have been trying to achieve the same gradient like fall off in corners for soo long now and i just cant. Default interiors just look so flat and i resort to blending AO in ps, but its just not the same.

Would you mind talking about how that was achieved? Any clues would be great!

2017-09-30, 03:04:48
Reply #62

dubcat

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These radius settings are at 1k, multiply K by whatever you are using.
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2017-09-30, 19:28:49
Reply #63

PROH

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Hi dubcat. I am trying to rebuild some old corona materials with the new BPR settings, and wanted to use your IOR excel shead, but I cant get permission to download it. So would it be possible to get you to make a new/different link to this (for example Dropbox)?

Best regards.

2017-10-02, 21:44:24
Reply #64

dubcat

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wanted to use your IOR excel shead

Hey!
Some folders on my google drive got messed up, I need to dig through the backup log and make new links.

--------------------------------------------------------------

I finally got around to make a real time high pass filter + albedo changer.
I've been using this technique for years in Photoshop, but now I can adjust everything live in IR!

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2017-10-03, 03:08:44
Reply #65

snakebox

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These radius settings are at 1k, multiply K by whatever you are using.

How on earth did you come up with these numbers?  just feels good or is there some science to it? (like most of the stuff you do :) )  interesting approach for sure, keep it up!

2017-10-03, 08:07:24
Reply #66

dubcat

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How on earth did you come up with these numbers?
They try to emulate the typical setting that Scandinavian interior photographers use in Lightroom. Lightroom still looks better, but it's nice to have a little preview in VFB while working.

-----------------------------------------------------------

I''v uploaded a new spreadsheet.
It has two tabs "Reflectivity and IOR" and "Size to Real World Size"
I added Unreal 4 conversion to the sheet earlier this year.



https://docs.google.com/spreadsheets/d/1jdENLgrX7r85zhumLMpzreNf11tmFuBhv3UXiEMgG1E/
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2017-10-03, 12:56:50
Reply #67

PROH

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Thank you so much :)

2017-10-03, 13:34:20
Reply #68

johnymrazko

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These radius settings are at 1k, multiply K by whatever you are using.

should only blur and sharpen radius be multiplied by k? or amount as well?

2017-10-03, 14:43:36
Reply #69

dubcat

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should only blur and sharpen radius be multiplied by k? or amount as well?

Only radius.
It's hard to tell if the radius parameters scale linearly, since we can't just scale the renders down and compare.
Sharpen in Corona is really harsh, even 0.001 sharpen radius crush blacks.

-----------------------------------

For people who tried to make a copy of the spreadsheet when I first uploaded it, try again now. The function was disabled for whatever reason.
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2017-10-03, 19:58:56
Reply #70

johnymrazko

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Thank you,

do you also know what would be the equivalent values in Lightroom?

2017-10-03, 20:41:04
Reply #71

dubcat

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These are the average values

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2017-10-06, 10:54:18
Reply #72

Fluss

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I find it strange to use LUT that is not related to the digital depth of the image rendered ?!
Maybe I'll release 64 sliced versions in the future, 41+ should be enough for what you want.

What cameras are used for the extracted LUT ?
I went into my Canon/Nikon folders and selected 3 random LUTs. I got a lot of Canon 60D LUTs in there, so one of them might be 60D.

Canon cameras have this magenta Tint to them, sometimes -10 green. This happens even if you calibrate the camera as perfect as you can. We need to use the sexy Tint feature in CameraRAW to get a perfect white balance. Since I'm dumping the real deal, I left this error in there. If you notice a slight magenta shift, it's a Canon LUT 99%.

Canons best friend.



and a big thanks to everyone else that has responded!

If you are a canon user, you should try magiclantern. It's a custom firmware that extends camera capabilities. There is a withe balance function that can actually correct the magenta shift.

Edit: http://www.magiclantern.fm/

2017-10-06, 23:18:38
Reply #73

lmikkelb

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Just one question, to clarify. We are viewing srgb and applying luts thats based on srgb right? good job with the luts and everything by the way, that corona mask thing looks amazing.
« Last Edit: 2017-10-07, 12:27:55 by lmikkelb »

2017-10-10, 13:05:05
Reply #74

dubcat

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srgb right?

Yes, viewed as sRGB :)
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2017-10-31, 16:38:57
Reply #75

dubcat

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Every now and then I get Megascans questions. I'm posting this here, so I can link to this post.

-== HDRi Setup ==-

Megascans use a HDRi named "Pisa courtyard nearing sunset, Italy" as default
You can get this HDRi for free here http://gl.ict.usc.edu/Data/HighResProbes/

If you want to mimic the Megascans preview images, set "U Offset" to -0.57
Remember to set "U Tiling" to -1, since 3dsmax project from the outside and flip our HDRi.



-== Mesh Setup ==-

Create a 2x2m Plane and tile it like this



-== Material Setup ==-


In this example I will use "Soil_Mud_pjuph20"

After you have extracted the .zip file with Bridge, you can double click the preview image and it will take you to the material folder.

Open Albedo and AO in Photoshop. Copy the AO map above Albedo and change the blending mode to "Multiply". Save it as AlbedoAO.



Megascans is made for PBR engines that use Specular.

0 Specular = 1 IOR
0.5 Specular = 1.5 IOR
1 Specular = 1.79 IOR

Since Corona is based on IOR, we have to convert the Specular map to IOR.
I've made a "Specular to IOR" LUT that gets shipped with Bridge, but it's kinda hidden.
You can find it here "C:\Program Files\Quixel\Megascans Bridge\Bridge_Data\Support\SpecularToIOR.CUBE"

Open the Specular map in Photoshop
Change the mode to 16bit
Add a "Color Lookup" layer and select "SpecularToIOR.CUBE"
Hit CTRL + Shift + E to flatten the layer stack
Change the mode back to 8bit and save it as IOR.




Inisde the material folder there is a ".json" file. Open this file in Notepad++ or whatever you use.
Search for "Height"
In this example the Height value is "0.042 m", convert this value to cm.
Our displacement height should be 4.2cm.



Load the maps like this.
"Flip Green" inside CoronaNormal.



Depending on how you want the displacement to behave, you can use Min 0 Max 4.2. Or Min -2.1 Max 2.1



-== Camera Setup ==-

If you want to mimic Megascans, you can place your camera like this.
24mm Focal Length.



-== Render Setup ==-

Set size to 1450x816.
Set "Secondary solver" to "Path  Tracing"
Reduce "Screen size (px)" until your pc start to smoke, then dial it back a little.



-== VFB Setup ==-

Set EV to 2.61 if you are using the same HDRi as me.
Megascans love their Vignette, so set it to 0.8
They also love to overdrive Sharpen, so set it to 10 !!!



-== Test Render ==-

Beauty



Direct



Reflection



Displacement



Displacement + Normal

« Last Edit: 2017-11-01, 00:10:04 by dubcat »
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2017-10-31, 18:49:54
Reply #76

romullus

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That's very interesting. I always thought that specular map is optional to plug into reflectivity slot, just to make occluded areas less shiny. I wonder how much of a difference it makes when converted in to IOR and plugged in to according slot?

By the way, is there some other way to convert specular to IOR, for those who doesn't have megascan bridge?
I'm not Corona Team member. Everything i say, is my personal opinion only.

2017-10-31, 19:04:51
Reply #77

hkezer

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Hey dubcat, I want to ask you a kind of technical question, which I cannot figure out exactly.

I have been using your LUTs almost like always :) then I wanted to try, https://masteringcgi.com.au/product/3d-collective-professional-filmic-luts/ this ones from Adan.

And there were 2 folders, sRGB and Linear. And they say, I should use sRGB in corona VFB, and in photoshop and vray I should use Linear. but I have no idea why. Can you a little explain the reason and how can I get the most out of it?
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2017-10-31, 20:19:05
Reply #78

dubcat

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Hey guys!

is there some other way to convert specular to IOR, for those who doesn't have megascan bridge?

I'm attaching my old LUT that is shipped with Bridge, and a new version that I generated a few weeks back.
The new version was generated with code and can remap any value. The old version was made manually and can go to IOR 8 or something like that. Photoshop 2018 doesn't like 3dl though.

This is without the IOR map

Beauty



Reflection, eeeeeww nasty.



Can you a little explain the reason and how can I get the most out of it?

A LUT looks at specific locations and then remap the RGB value to a new value. sRGB has a gamma curve, so you have to use LUTs that are made for that gamma.

Corona use sRGB
Photoshop use sRGB for 8/16bit and Linear for 32bit.

Here is a quick demonstration, so you can see the difference. Both use the same sRGB LUT 100%.



If you only have sRGB LUTs, but want to use them on a linear image, you can use this dirty little hack.
If I had done this to the Linear example above, it would look identical to the sRGB example.

« Last Edit: 2017-10-31, 23:10:38 by dubcat »
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2017-10-31, 22:27:23
Reply #79

PROH

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Hi Dubcat. Is there anyway to convert secular to IOR inside Max/Corona? I tried using a Corona output map with your LUT (cube), and got something decent, but not quite right. Can this be done somehow?

2017-10-31, 22:32:45
Reply #80

romullus

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Thank you very much! Do you know, how they come up with that specular/IOR map? Everyone is telling that PBR workflow is ~1,5 IOR for dielectrics and reflection all the way to the max, but from your examples it's pretty obvious, that some variance in IOR, does wonders to final result.
I'm not Corona Team member. Everything i say, is my personal opinion only.

2017-10-31, 23:00:30
Reply #81

dubcat

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Hey

and got something decent, but not quite right

This!
I actually asked Ondra a week or two ago if there was a bug inside CoronaOutput. Because the result is always off by a few RGB, and these IOR values are super sensitive.
I have tried to load the bitmap as 1.0/2.2, convert in and out of gamma. The values are always a little off.

Do you know, how they come up with that specular/IOR map?

Open one of the specular maps inside Photoshop as 32bit, sample the values



In this case it is 0.0358

0.0358 * 100 = 3.58% Reflectivity
(1+SQRT(0.0358))/(1-SQRT(0.0358)) = 1.47 IOR

No idea how they scan it.
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2017-11-01, 00:02:33
Reply #82

PROH

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Thank you :) So far my best converting result inside Max/Corona is this:

- Load Gloss map with gamma 2.2, and put this into a Corona Output Map
- Set "Affected by tonemapping" ON
- Load "Specular to IOR.cube" LUT, with opacity 1
- Set gamma to 0,5 (this value is purely by eyeballing)

Will do some more testing later...

2017-11-02, 16:31:46
Reply #83

dubcat

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This setup generates proper IOR maps
Enable "Affected by VFB"

« Last Edit: 2017-11-03, 00:00:31 by dubcat »
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2017-11-02, 22:03:06
Reply #84

PROH

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Thank you so much. I see now that I wrote "gloss map" instead of "specular map" in my previous post :(

I've tried your setup, and if EXposure is anything else than 0 (with a calibrated HDR) then I only get a good/realistic result when "Affected by VFB" is activated. Probably need to test a bit more...

Thanks for sharing your knowledge:)

2017-11-02, 23:59:52
Reply #85

dubcat

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I've tried your setup, and if EXposure is anything else than 0 (with a calibrated HDR) then I only get a good/realistic result when "Affected by VFB" is activated.

Thanks. I only tested on EV 0.
Updated my last post.

edit:
We really need to get this sorted, there is no reason why EV should impact a material map :|
« Last Edit: 2017-11-03, 06:23:02 by dubcat »
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2017-11-03, 10:00:12
Reply #86

Jpjapers

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These radius settings are at 1k, multiply K by whatever you are using.

This is cool.
Just so im understanding correctly then, how would you calculate the settings for a 4k image? Youd just multiply those numbers by 4?
Or am i misunderstanding completely?
Show your working please :D
« Last Edit: 2017-11-03, 11:59:11 by jpjapers »

2017-11-17, 03:58:39
Reply #87

dubcat

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just multiply those numbers by 4?

I don't know if the values scale linearly with render size, we need someone from the dev team to answer this. I just use the settings as a place holder in IR, and then do the real sharpening in Lightroom.

-----------------------

-5.65 EV is the value for default peak sun / corona sky. If you guys want to calibrate your HDRis.

-----------------------

edit:

Sharpen amount 10 / sharpen radius 1.0 seem to be consistent with Lightroom 150.
« Last Edit: 2017-11-17, 04:13:20 by dubcat »
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2017-11-24, 23:43:43
Reply #88

dubcat

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I was tired of the default material sphere that stretch materials all over the place. Here is a little guide on how to make a good looking material sphere.

Create a GeoSphere 50cm radius, since most scans nowadays are 1 meter.
128+ segments.
Type "Octa"



Throw a "Spherify" on there just to be safe



Add a "UVW Map" "Planer" mode



Default Sphere, nasty



Box turned in to a sphere



GeoSphere with Planar

« Last Edit: 2017-11-25, 02:13:59 by dubcat »
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2017-11-25, 19:48:11
Reply #89

dj_buckley

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Jeez this thread is difficult to follow - to many subjects being discussed and replies to question multiple posts up without quoting the original question.  My head is gonna explode.  It's like opening a WhatsApp group after not following it for a year haha.  Sounds like good stuff though

2017-11-29, 04:33:01
Reply #90

vicmds

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Every now and then I get Megascans questions. I'm posting this here, so I can link to this post.

Thanks for sharing. Curious to know what your process to mimic them would look like for their (excellent) 3d plants, since their previews are apparently all UE4. Same material setup?

2017-12-01, 16:30:34
Reply #91

dubcat

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Same material setup?

3D models ship with baked albedo+ao texture maps, so you can skip the merging part.
For Translucency Fraction I usually use a value from 0.3-0.4.
Sometimes the translucency maps work out of the box. Sometimes you have to boost the gain/reduce saturation/change the hue to taste.
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2017-12-08, 01:21:04
Reply #92

dubcat

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I noticed that I didn't specify the blending modes. The first height map blend is "Lighten", and the second blend is the lighten mix "Subtracted" from the top layer.
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2017-12-08, 09:51:04
Reply #93

romullus

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Didn't notice if mentioned before, but does blending has to be performed in linear or in sRGB space?
I'm not Corona Team member. Everything i say, is my personal opinion only.

2017-12-14, 20:40:07
Reply #94

dubcat

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sRGB space?
I need to find the max file to be 100% sure, but I think they all were linear.

----------------------------------------------------------------------------------------

I've remade the ACES Tonemapper with default settings in Photoshop.
The only thing you have to do, is to open your 32bit .hdr/.exr files in Photoshop and run the action.

Remember to leave "Highlight Compression" at 1 in Corona.

Raw



Photoshop Voodoo



ACES Tonemapped

« Last Edit: 2017-12-15, 02:19:44 by dubcat »
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2017-12-16, 21:15:43
Reply #95

bluebox

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Can this be baked into LUT file for use inside Corona ?

2017-12-16, 23:38:30
Reply #96

romullus

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Can this be baked into LUT file for use inside Corona ?
+1
I'm not Corona Team member. Everything i say, is my personal opinion only.

2017-12-18, 22:09:45
Reply #97

dubcat

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Can this be baked into LUT file for use inside Corona ?

I'll post the log LUT when the Corona log LUT loader gets fixed.

This is how it should work

Linear Render



Linear converted to Cineon log, same as Corona.



Apply tonemapper LUT



Convert back to linear



View as sRGB



But this is what we get in Corona right now, using the same tonemapper LUT as above.

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2017-12-19, 02:09:07
Reply #98

agentdark45

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Can this be baked into LUT file for use inside Corona ?

I'll post the log LUT when the Corona log LUT loader gets fixed.[/img]

Devs can we get this done in a daily build? (says the guy that has zero idea how hard this is to implement).
Vray who?

2017-12-19, 07:45:24
Reply #99

bluebox

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Can this be baked into LUT file for use inside Corona ?

I'll post the log LUT when the Corona log LUT loader gets fixed.[/img]

Devs can we get this done in a daily build? (says the guy that has zero idea how hard this is to implement).

+1 Yes please!

Or can someone who knows what to request make a feature request :D ?

BTW, thank you Dubcat for all your research !

2017-12-19, 09:41:19
Reply #100

maru

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I'll post the log LUT when the Corona log LUT loader gets fixed.
Is this blackmailing? :D

Now seriously, is this officially logged somewhere outside of this forum thread, or discussed directly with Ondra?

2017-12-19, 17:10:13
Reply #101

dubcat

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Is this blackmailing? :D

Hehehe, just want to be sure I'm sharing something that is actually working ;)

Now seriously, is this officially logged somewhere outside of this forum thread, or discussed directly with Ondra?

The devs know about it, but I've made a new mantis report.
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2017-12-21, 03:10:27
Reply #102

dubcat

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I'm compiling a tonemapper pack for you guys.
The funny thing is that all the top tonemappers out there kinda look the same on the curve, but they look so different on the final render.

Here is a little teaser.

Secret Render Engine



ACES



Camera RAW 2012 (The one I've been using for years, for compression).

« Last Edit: 2017-12-21, 04:38:44 by dubcat »
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2017-12-21, 12:57:08
Reply #103

nkilar

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What I can I say dubcat, can't wait to see what you got cooking. It is much appreciated, Sir! :)

2017-12-29, 08:23:29
Reply #104

bluebox

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Hey there Dubcat, how's work on those luts :D ? Can't wait to try them out. Thanks man !

2018-01-11, 22:36:26
Reply #105

dubcat

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Hey there Dubcat, how's work on those luts :D ? Can't wait to try them out. Thanks man !

Hey!

The LUTs have been ready since December, just waiting for the devs to fix the loglut loader :)

edit:

These LUTs will compress and adjust contrast. Tonemappers like ACES also change how light intensity behaves, to do this we have to change color matrix.

Here is an example made by Koola, from the Unreal 4 community.



ACES does a pretty good job at emulating how light intensity behaves, but it still has a bug with blue light. Blue turns into pink instead of cyan. fStorm has a custom matrix that correct this problem. Currently Corona does not change how light intensity behaves, so pure Red/Green/Blue will still be pure Red/Green/Blue. Stuff will look like "UE4 - Exp 0" no matter what you do.
« Last Edit: 2018-01-12, 04:34:57 by dubcat »
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2018-01-13, 00:26:08
Reply #106

serch

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The LUTs have been ready since December, just waiting for the devs to fix the loglut loader :)
u do.

Are devs actually working on the fix?

2018-01-13, 07:55:55
Reply #107

oddvisionary

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Instead of fixing LUT it would be better if they simply add support for OCIO. I can't trust LUT for this kind of stuff. I prefer having a trusted color management system like OCIO (works like a charm in Arnold C4D, no LUT).

LUT should just be used for pre-viz grading.
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2018-01-13, 15:03:10
Reply #108

bluebox

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Thanks Dubcat :), asked if Devs are working on this topic in the daily builds topic. We'll see how it goes.

As for using LUTs only for previz grading - if something works out of the box then why overcomplicate it ;) ?

2018-01-13, 15:48:43
Reply #109

Juraj Talcik

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Instead of fixing LUT it would be better if they simply add support for OCIO. I can't trust LUT for this kind of stuff. I prefer having a trusted color management system like OCIO (works like a charm in Arnold C4D, no LUT).

LUT should just be used for pre-viz grading.

Dubcat and everyone is well aware of this, but adding full color-management has been requested for more than two years. It just doesn't feel like it will happen anytime soon, so any hack in mean-time would still be very welcome addition. Yes, LUT has certain primary use, but that doesn't mean it can't be used outside of the box for anything else.
Heck, even the main tech luminaries behind game dev like John Hable suggested LUT to be ok solution for tonemapping.

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2018-01-16, 09:34:25
Reply #110

oddvisionary

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Instead of fixing LUT it would be better if they simply add support for OCIO. I can't trust LUT for this kind of stuff. I prefer having a trusted color management system like OCIO (works like a charm in Arnold C4D, no LUT).

LUT should just be used for pre-viz grading.

Dubcat and everyone is well aware of this, but adding full color-management has been requested for more than two years. It just doesn't feel like it will happen anytime soon, so any hack in mean-time would still be very welcome addition. Yes, LUT has certain primary use, but that doesn't mean it can't be used outside of the box for anything else.
Heck, even the main tech luminaries behind game dev like John Hable suggested LUT to be ok solution for tonemapping.

For sure! I tried a lot of color management LUT tests. I stopped and instead focused on a post-workflow. I just export un-tonemapped renders (openEXR) and do the rest in Davinci Resolve/Fusion or After Effect which some of them have a full color management system built in.

I requested OCIO (like Arnold Color management) they didn't said anything yet : https://corona-renderer.com/forum/index.php?topic=18169.msg114140#msg114140

I use OCIO with Arnold, works very well! I can even edit and "write" my own LUT and configs and the ACES official forum is full of information about ACES in CGI. Hoping to get it to Corona as well soon or later (more later, I think Node graph is more a priority right now in C4D).
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2018-01-16, 23:51:13
Reply #111

Njen

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For sure! I tried a lot of color management LUT tests. I stopped and instead focused on a post-workflow. I just export un-tonemapped renders (openEXR) and do the rest in Davinci Resolve/Fusion or After Effect which some of them have a full color management system built in.

This is exactly my workflow as well, simple and uncomplicated to just render out linear exr's and then comp them together in Nuke, a program I 100% trust for colour management (with the right tools).
Please support my Kickstarter for my animated film, Cyan Eyed (rendered in Corona)!

2018-01-17, 00:17:02
Reply #112

oddvisionary

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For sure! I tried a lot of color management LUT tests. I stopped and instead focused on a post-workflow. I just export un-tonemapped renders (openEXR) and do the rest in Davinci Resolve/Fusion or After Effect which some of them have a full color management system built in.

This is exactly my workflow as well, simple and uncomplicated to just render out linear exr's and then comp them together in Nuke, a program I 100% trust for colour management (with the right tools).

LUT should be used like in real life, for movies etc. They have a camera (more than one obviously) they apply a custom lut made on set by an on set colorist, so they can a pre-color graded look of the shot (more immersive for the direction/DOP).

Same for CG, I use LUT just to check out how it would be with some post or mood. It can be handy to do everything in the frame buffer, but best solutions is always post.

Nuke is for sure a trusted software for that, and complete with OCIO/ACES/FILMIC.
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2018-01-17, 00:51:33
Reply #113

agentdark45

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Hey there Dubcat, how's work on those luts :D ? Can't wait to try them out. Thanks man !

Hey!

The LUTs have been ready since December, just waiting for the devs to fix the loglut loader :)

edit:

These LUTs will compress and adjust contrast. Tonemappers like ACES also change how light intensity behaves, to do this we have to change color matrix.

Here is an example made by Koola, from the Unreal 4 community.

[img width=500 height=340]https://i.imgur.com/zSj6y79.jpg[img]

ACES does a pretty good job at emulating how light intensity behaves, but it still has a bug with blue light. Blue turns into pink instead of cyan. fStorm has a custom matrix that correct this problem. Currently Corona does not change how light intensity behaves, so pure Red/Green/Blue will still be pure Red/Green/Blue. Stuff will look like "UE4 - Exp 0" no matter what you do.

This is such a huge part of rendering I really don't know why we aren't looking into this with greater detail.

Please devs can we bump this up on the priority list?

How about a simple check box to unlock an "advanced tone mapper". That way all previous files render exactly the same, but for those that want to go further we have some more options (which doesn't clutter the UI by default).
Vray who?

2018-01-17, 13:59:06
Reply #114

Juraj Talcik

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How about a simple check box to unlock an "advanced tone mapper". That way all previous files render exactly the same, but for those that want to go further we have some more options (which doesn't clutter the UI by default).

Yup, full (and correct this time) filmic this way would be great.

Maybe in 2020 :- )
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2018-01-17, 14:23:22
Reply #115

oddvisionary

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.
« Last Edit: 2018-09-23, 03:17:04 by oddvisionary »
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2018-01-17, 17:20:16
Reply #116

Rhodesy

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Yes I think the C4D dev team is separate to the main Corona app. Also the tone mapping would quickly come to both as they use the same frame buffer window.

2018-01-19, 03:52:55
Reply #117

dubcat

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I want to state that all my posts are directed to still image architectural visualization. The stuff I post is not directed for people who use a "pipeline", like CGI film. I need to get quick and good results straight out of the frame buffer. I like to think of VFB as a photo, and then I can open the "photo" in Lightroom/CameraRaw and do the final tweaks if I want to. The logLUTs are a temporarily "hack" solution, until Corona can get a more advanced tonemapper with custom matrix. It's not a question if Corona should get a new tonemapper or not, but when. Currently I use my own custom scripts in Fusion, but I really don't want to. fStorms tonemapper is superior in every way right now. It has a shoulder, it has a toe. It adjust light intensity according to real photos. It has a custom matrix that takes care of the blue turns to pink problem. It might not be 100% photo correct, but it's not pink. I only use Corona, and it hurts to say this, but it's the truth. We are not on top of the food chain when it comes to tonemapping, and there is no reason why. Corona Team = Best Team.

edit: fixed some typos, damn you auto correct!
« Last Edit: 2018-01-19, 04:58:22 by dubcat »
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2018-01-19, 16:15:17
Reply #118

agentdark45

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I want to state that all my posts are directed to still image architectural visualization. The stuff I post is not directed for people who use a "pipeline", like CGI film. I need to get quick and good results straight out of the frame buffer. I like to think of VFB as a photo, and then I can open the "photo" in Lightroom/CameraRaw and do the final tweaks if I want to. The logLUTs are a temporarily "hack" solution, until Corona can get a more advanced tonemapper with custom matrix. It's not a question if Corona should get a new tonemapper or not, but when. Currently I use my own custom scripts in Fusion, but I really don't want to. fStorms tonemapper is superior in every way right now. It has a shoulder, it has a toe. It adjust light intensity according to real photos. It has a custom matrix that takes care of the blue turns to pink problem. It might not be 100% photo correct, but it's not pink. I only use Corona, and it hurts to say this, but it's the truth. We are not on top of the food chain when it comes to tonemapping, and there is no reason why. Corona Team = Best Team.

edit: fixed some typos, damn you auto correct!

All of the above x2

If you check the gallery, most guys on the forums are posting archviz stuff made using 3ds max. Only a small minority of Corona users are messing with Nuke e.t.c. I don't see why improving the tonemapping features of Corona to make it on par, or even surpassing the quality of F-Storm somehow detracts from the functionality for the compositing guys (it will still be there if you want it).

I'd bet my left arm that most people want an all in one solution that can produce the prettiest images out of the box, with the least amount of hassle.

This is also why I stick with Corona and don't go full into F-Storm, there are too many limitations with it despite it producing very photorealistic images.
Vray who?

2018-01-19, 19:36:18
Reply #119

bluebox

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Exactly. If you want to go pro, you still can.

As we work closely with interior designers  there is also the aspect of the images being exactly the same throught many many preview turns.
I can't imagine editing say 30 shots each time with external software, caring to maintain contrast etc. at the same level. Therefore (at least for us) getting the most straight out of VFB is very important.

2018-01-19, 22:29:12
Reply #120

zuliban

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I gave up along time ago in renders VFB i just use the lineal image as open exr and do the rest in nuke.
Still renders need small tech improvements like a correct DOF, cat eyes effect and obstruction  refraction, dof where you can see some small rainbow in some bokeh shapes and some hairs obstruction from grass in other shapes, a more correct material that preserves energy on bump and so on it.
It also would be nice to have this correct tone mapping that can mimics real world cameras and old school films.

And of course caustics... i feel nobody is looking at this anymore (corona roadmap have them)they really brings a image to life when it has enough glass or reflective surfaces.
I also have tested fstorm and i agree it feels like a real camera inside a render and create very realistic fast renders, but still i don't like the gpu low memory limitation make them really unusable for big textures or closeups maybe in some years we can have some nice 64gb cards and if miners are cool a good price range.

I also have seen some tech from Arion render and it has alot of nice features that other renders don't have like the dof obstruction and better materials i wonder why people don't use that render?
i tested it when it introduced bloom and glare before any other render then they deteached it to arionfx plugin.

2018-01-22, 16:32:29
Reply #121

oddvisionary

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I gave up along time ago in renders VFB i just use the lineal image as open exr and do the rest in nuke.
Still renders need small tech improvements like a correct DOF, cat eyes effect and obstruction  refraction, dof where you can see some small rainbow in some bokeh shapes and some hairs obstruction from grass in other shapes, a more correct material that preserves energy on bump and so on it.
It also would be nice to have this correct tone mapping that can mimics real world cameras and old school films.

And of course caustics... i feel nobody is looking at this anymore (corona roadmap have them)they really brings a image to life when it has enough glass or reflective surfaces.
I also have tested fstorm and i agree it feels like a real camera inside a render and create very realistic fast renders, but still i don't like the gpu low memory limitation make them really unusable for big textures or closeups maybe in some years we can have some nice 64gb cards and if miners are cool a good price range.

I also have seen some tech from Arion render and it has alot of nice features that other renders don't have like the dof obstruction and better materials i wonder why people don't use that render?
i tested it when it introduced bloom and glare before any other render then they deteached it to arionfx plugin.

You should try Indigo Render for caustics. The best for now, and they use MTL (Metropolis Light Transport) algorithm calculation, that are not implemented to Corona, which is why Corona caustics are nice but not the best.

You can get better caustics when using experimental settings : Bidir/VCM (if I remember correctly, I only tried once to use it for tests).
« Last Edit: 2018-09-23, 03:20:25 by oddvisionary »
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2018-01-23, 00:20:50
Reply #122

snakebox

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You should try Indigo Render for caustics. The best for now, and they use MTL (Metropolis Light Transport) algorithm calculation, that are not implemented to Corona, which is why Corona caustics are nice but not the best.

I don't mean to hijack the topic, but I was pleasantly surprised by Redshifts caustics.

small test to demonstrate:
https://vimeo.com/239298771

It's still a post process like in vray I believe, but I found them much easier to use and also liked the result better. Caustics in Corona does not make sense to me, doesn't give me what I expect nor do I feel like I have any control. Hopefully that changes one day.

2018-01-23, 10:57:56
Reply #123

romullus

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I'm not Corona Team member. Everything i say, is my personal opinion only.

2018-01-26, 01:47:22
Reply #124

dubcat

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This is from an older post I made on the forum somewhere, but I want to consolidate all the important stuff in this thread.

This is how Corona behaves today.



This is default fstorm.



These are fstorm with adjusted parameters.



fStorm at 0.99 is the same as current Corona



I just want to state again that I'm not trying to provoke, I don't like to make 1:1 comparisons between render engines. I'm posting all these findings because I think it will improve Corona as a render engine. Corona Team, you know I love you.

fStorm split the HDRi into indirect and direct pass, and I think this is the reason fStorm has different shadow values. I've talked to the Corona dev team, and they have ensured me that Corona use the correct method. So ignore the value difference, this post is about the diffuse roughness. I've made my own custom Corona to fstorm and fstorm to Corona converter, and when it comes to interior renders, diffuse roughness has a lot to say on the final render. This is a parameter that should not be overlooked by the dev team.
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2018-01-26, 01:54:00
Reply #125

Dionysios.TS

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+1
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2018-01-26, 15:24:48
Reply #126

Fluss

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Dubcat I don't understand what you're trying to demonstrate in your last post. Can you explain a little bit further pls?

2018-01-26, 15:43:34
Reply #127

romullus

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Open images in new tabs and switch between them. Look at sphere's shadow terminator - the difference should be obvious.
I'm not Corona Team member. Everything i say, is my personal opinion only.

2018-01-27, 17:22:25
Reply #128

dubcat

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Can you explain a little bit further pls?

As romullus said :)

--------------------------------------------------------------

I'm posting a little weekend present for you guys, these settings emulate the default ACES tonemapper with about 0.5 RGB error.
The settings might look ridiculous with negative "highlight compression", but trust me, give it a try ;)



I'm attaching a VFB settings file that you can load.
Remember to disable LUT if you are using one.

edit: I made these settings with "Corona 2018-01-25 Daily". I remember there were some filmic changes, but I can't remember if it was 1.6/1.7 or daily. Just letting you know in case stuff looks weird. The result should be pretty much identical to the ACES Photoshop script I posted earlier.
« Last Edit: 2018-01-28, 03:59:30 by dubcat »
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2018-01-28, 15:42:46
Reply #129

agentdark45

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I just tried out the above settings (with tweaked exposure) on some previous CXR's and I have to say I'm super impressed with the result!

Straight out of the VFB I'm getting some very pleasing images. Nice natural burnouts, good contrast/shadows and rich colours. We are definitely on to something here.

Comparison images below:

1. Default Corona settings with highlight compression at 8
2. Manually tweaked settings (no lut)
3. Manually tweaked settings (with lut)
4. Dubcat's settings
« Last Edit: 2018-01-28, 15:56:19 by agentdark45 »
Vray who?

2018-01-28, 21:31:23
Reply #130

Fluss

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Open images in new tabs and switch between them. Look at sphere's shadow terminator - the difference should be obvious.

Indeed, the transition between light and shadow is way softer in Fstorm. Much more pleasing to the eye.

How does the Vray alSurface shader does compare to this?

"The Fresnel effect is computed as part of the BRDF calculations (a.k.a. “glossy Fresnel”) and takes into account the viewing direction, the surface normal, and the light directions."

Isn't it related to this ?
nothing to do with the diffuse part, misread what you wrote

Also, As far as I remember, Corona shader does not support glossy fresnel.




What's more, some users are experiencing strange atifacts with SSS here :

https://corona-renderer.com/forum/index.php?topic=18702.0

Which seems to be the exact same issue descibed here :

Quote
VRay Skin Mtl: This uses a two lobe specular model with a sharp and broad reflection. It also uses Phong as the reflective BRDF. This model proved to work well in many situations, but at glancing angles, based on the way that it would cut out the SSS, could cause darkening. This is because the Fresnel effect is computed as a function of the angle between the viewing direction and the surface normal, ignoring the directions from which lights illuminate the surfaces.

alSurface: This model also uses a two lobe specular model. However, instead of using a smooth BRDF like Phong or Blinn, it uses a microfacet one. The Fresnel effect is computed as part of the BRDF calculations (a.k.a. “glossy Fresnel”) and takes into account the viewing direction, the surface normal, and the light directions. The user has a choice between GGX and Beckmann BRDF models. Based on the nature of the micro faceting, it can avoid the darkening effect at the glancing angles through retro-reflection. Additionally it does not cover the SSS at the same glancing angles.

source : https://www.chaosgroup.com/blog/v-rays-implementation-of-the-anders-langlands-alsurface-shader

Of course, I might be totally misleading as i'm not a tech guru like some of you guys..

But there is one thing that bother me. We were experiencing some white halos on rough shaders some times ago. By looking at the examples here ( https://www.chaosgroup.com/blog/understanding-glossy-fresnel), it looks like a direct consequence of not supporting the glossy fresnel effect. It seems fixed now. But when i see that glossy fresnel isn't supported yet, i wonder if it has been fixed the correct way or with some workarounds (we have then seen some dark halos when the devs were trying to fix it, which strengthens me in my view that it wasn't done the right way).

Basically, initial implementation of the shader was good, it should be more reflective at grazing angles like it was doing BUT this effect should also be affected by the roughness as more micro-facets are facing the camera (so less grazing angles) on rough materials compared to shiny ones. If the whole thing is well implemented, angle affect should resolve by itself I guess.

fStorm split the HDRi into indirect and direct pass, and I think this is the reason fStorm has different shadow values.

That said, your statement totally make sense here.
« Last Edit: 2018-02-03, 16:48:51 by Fluss »

2018-01-29, 09:16:51
Reply #131

NicolasC

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Thanks A LOT Dubcat for all your investigations. Very instructive, a gold mine.
Hats off, really.
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2018-01-29, 17:05:05
Reply #132

Juraj Talcik

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it has been fixed the correct way or with some workarounds

It was some sort of workaround by manually fitting it to resemble the alsurface curve. And the diffuse part is still basic Lambert, which is responsible for the harsch look.

Ondra said he would like to look into this more now, not sure when that is but we should keep the pressure and push him towards it :- ).
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2018-01-31, 00:53:07
Reply #133

Dippndots

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Is your Megascans export script still available, Dubcat? The link in your Megascans thread 404s :(

2018-01-31, 10:15:48
Reply #134

Fluss

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it has been fixed the correct way or with some workarounds

It was some sort of workaround by manually fitting it to resemble the alsurface curve. And the diffuse part is still basic Lambert, which is responsible for the harsch look.

Ondra said he would like to look into this more now, not sure when that is but we should keep the pressure and push him towards it :- ).

Hopefully, corona 2.0 will bring Vray compatibility and OSL support so we might be able to try that alshader inside corona sooner than later.

2018-01-31, 10:29:55
Reply #135

Juraj Talcik

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OSL doesn't have access to BRDF though so I am not sure if we would get anything else than the values translated to CoronaMTL internally.
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2018-01-31, 11:25:22
Reply #136

Fluss

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OSL doesn't have access to BRDF though so I am not sure if we would get anything else than the values translated to CoronaMTL internally.

Just checked, you're right OSL does not allow to write custom BRDF / can only use what's available... That's sucks! So we have to wait for a proper 'state of the art' BSDF.

I was so optimistic ! Juraj you just ruined my day :)

2018-02-01, 09:04:18
Reply #137

Fluss

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dubcat, can you share your scene pls ? I'd like to make some direct comparison with Vray alshader.





2018-02-01, 16:43:24
Reply #138

dubcat

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We are definitely on to something here.

Glad you like it. :)

Thanks A LOT Dubcat

Thank you :)

Is your Megascans export script still available, Dubcat? The link in your Megascans thread 404s :(

I've been working on new scripts for Quixel since last winter.
The new scripts use my "Specular to IOR v2" LUT to auto convert specular maps, and they read the proper displacement height value from the json file.
I don't have a release date, but it will be worth the wait!

I'll make a new post here to inform you guys when it's released.

dubcat, can you share your scene pls ?

That scene is long gone, but I've made a new one for you. The zip contains a "Corona Sky" HDRi for consistent lighting and an fbx with geo/camera.
I had to use an external file sharing service, because the forum cap is at 30mb.

https://www.sharebase.net/58ed6f5e1e79212f



Hope I didn't miss any questions, if so, let me know.

edit:
I forgot to mention that Epic has fixed the blue light problem in Unreal.



edit edit:
Here is the ACES tonemapper if anyone is interested.

https://www.desmos.com/calculator/h8rbdpawxj

If you look at the numbers on the left side of each column, these are the parameters.

4   - Slope        - 0.88
7   - Toe           - 0.55
8   - Black Clip  - 0
11 - Shoulder   - 0.26
12 - White Clip - 0.04
« Last Edit: 2018-02-02, 03:47:00 by dubcat »
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2018-02-03, 12:45:55
Reply #139

Fluss

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Thanks dubcat for the scene. I'll make some comparison with shaders that support diffuse roughness
« Last Edit: 2018-02-03, 16:45:13 by Fluss »

2018-02-04, 12:58:56
Reply #140

Fluss

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I've finally made some test on the diffuse shading. Indeed, Corona seems to use pure Lambertian diffuse shading model which is suitable to describe high glossiness materials. When it comes to rougher materials, the oren-nayar model is more suitable.

example :



Arnold and redshift both use the oren-nayar diffuse shading model and then, expose a diffuse roughness parameter.

When diffuse roughness is set to 0, then it's pure Lambertian. As far as this value is changed, it switches to the Oren-Nayar implementation. You can see examples below (don't mind the little exposure difference between renderers, I matched them by eye, really quickly).

I did not find a Fstorm demo installation but from what I've seen from dubcat's tests, the Fstorm diffuse shading model seems quite off compared to other solutions. Don't know what algorithm is used there. Also noticed some strange artifacts on the sphere highlight in arnold when using strong roughness values. Redshift implementation seems to be the more consistent one.

Vray's diffuse roughness is completely off and I now understand why nobody (including me) uses it...

Also, to clarify things, diffuse roughness is not the same as glossy roughness. Most materials cap around 0.3 and shouldn't go over 0.5. From what I've found over the web, some artist tends to use a basic rule to get reliable results: diffuse roughness = glossy roughness * 0.33. There is something to dig in here.

It would be really nice to get diffuse roughness and glossy fresnel to be part of corona in the near future! Please!


2018-02-04, 15:07:39
Reply #141

Fluss

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one more test, Redshift , Lambertian vs Oren-Nayar diffuse shading :

Glossy roughness @0.7 - Diffuse Roughness @0.0

Glossy roughness @0.7 - Diffuse Roughness @0.23 -> 0.7*0.33 as explained above

Glossy roughness @1.0 - Diffuse Roughness @0.0

Glossy roughness @1.0 - Diffuse Roughness @0.33
« Last Edit: 2018-02-04, 16:28:02 by Fluss »

2018-02-05, 09:56:59
Reply #142

Juraj Talcik

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F-Storm does almost 100perc. use Oren-Nayar diffuse shading, or some in-house but nonetheless based on it (like their copy of GGX).

The most interesting approach is what the Disney guys (Brent) have done. They manually fitted the model so that rough materials have some retroreflection.

I generally like what they do (test and see when it matches reality) instead of just adding code and ending up with unrealistic crap. Lambert has to go.
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2018-02-05, 10:06:10
Reply #143

pokoy

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A few users were asking for Oren-Nayar on a regular basis, probably too few to be heard. It's really needed for a lot of surfaces, I'd be really happy if we got an improved shading model.

Thanks for the test images - from all the tests, Redshift's version looks best to me. Kind of surprising since I find many of their gallery images to look quite artificial, I always thought their shading model isn't as nice as Corona's.

2018-02-05, 10:44:10
Reply #144

Juraj Talcik

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Redshift still suffers from this odd reputation because their early user-base didn't focus on photorealistic work that much.

But their 2nd version came with state-of-art PBR shader with multiple brdf selection in 1/10 fraction of the time it took Corona to even fix GGX halo ;- ).
It was basically flawless, perfection.
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2018-02-05, 11:42:33
Reply #145

Fluss

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The most interesting approach is what the Disney guys (Brent) have done. They manually fitted the model so that rough materials have some retroreflection.

I generally like what they do (test and see when it matches reality) instead of just adding code and ending up with unrealistic crap. Lambert has to go.

I've also read the disney paper, the approach is indeed quite interesting. The only thing that bother me in this shader is the specular control which stands in lieu of an explicit index-of-refraction. Except that, it looks like a fantastic shader to work with. Renderman is Full-featured and free for non-commercial use, just need to grab a demo version of maya to test that out.

I finally managed to test Fstorm and I have to say that I'm quite impressed! Everything feels so natural, and not only on the diffuse part, glossy fresnel is a no brainer here! I'll dig into it a bit further.

F-Storm does almost 100perc. use Oren-Nayar diffuse shading

I'm not sure about that. It's default 0.8 and seems to be "Lambertian-like" at 0.99. It's also capped to 0.5. What's more, transition between light and shadows is tremendously softer.


A few users were asking for Oren-Nayar on a regular basis, probably too few to be heard. It's really needed for a lot of surfaces, I'd be really happy if we got an improved shading model.

Thanks for the test images - from all the tests, Redshift's version looks best to me. Kind of surprising since I find many of their gallery images to look quite artificial, I always thought their shading model isn't as nice as Corona's.

A better diffuse model is highly needed to get rid of that rough surface plastic look.

After some more tests, I'm a bit skeptical about redshift's implementation as it's quite noticeable in the highlighted parts but it does almost nothing in the shadows. Arnold looks weird on extreme values but it also significantly changes the diffuse appearance in the shadows which looks more convincing to my eye. It's more noticeable on the happy Buddha, I'll post some more experiments later.

2018-02-05, 14:04:11
Reply #146

Fluss

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Juraj, can you PM me ? I'd like to discuss some stuff with you if you don't mind

2018-02-05, 15:24:56
Reply #147

nkilar

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Juraj, can you PM me ? I'd like to discuss some stuff with you if you don't mind

I'm a lurker here (without much to say) and I really appreciate you guys going at it - going at the problem that is. :) That said, the more public spamming you guys do the better - I really enjoy reading the findings you smart people come up with. Hurrah! Thank you!

2018-02-05, 23:47:08
Reply #148

oddvisionary

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Juraj Talcik : F-storm + their? No, it's just one guy haha.
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2018-02-06, 10:39:23
Reply #149

Juraj Talcik

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Yeah I also prefer to bounce opinions public :- ). That's what threads like this are for. Don't worry the devs are not that sensitive and need some push :- )

But if it's something reeally private like just use my old mail juraj(dot)talcik (at) yahoo (com).
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2018-02-06, 13:08:34
Reply #150

Fluss

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Juraj, can you PM me ? I'd like to discuss some stuff with you if you don't mind

I'm a lurker here (without much to say) and I really appreciate you guys going at it - going at the problem that is. :) That said, the more public spamming you guys do the better - I really enjoy reading the findings you smart people come up with. Hurrah! Thank you!

Don't worry, will still sharing stuff here, just wanted to ask some hints to go further on the specular part without polluting the thread too much with trial and errors. Anyway, we're talking diffuse roughness, for now, let's see that later..

Here is another test to demonstrate the diffuse roughness contribution in Arnold. Diffuse shading is way smoother, diming light at F(0°) (which give the plastic look) and eliminating the black fringe Lambert tends to produce at grazing angles. Also, note that the whole thing appears to be darker, both tests were rendered in the same lighting and exposure condition. The shader is supposed to be energy conservative tho, that's just that diffuse rays are more scattered resulting in fewer rays hitting the camera hence darker render I guess.

edit: also grabbed a copy of the latest blender version which provides an implementation of the Disney uber shader. Will be interesting to see what it brings to the table :)
« Last Edit: 2018-02-06, 13:16:54 by Fluss »

2018-02-08, 15:45:00
Reply #151

Fluss

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Hey guys, I've made some more tests across different renderers to compare diffuse roughness at min/max values. Diffuse only, no specularity involved, here is what we get :











We can see that Fstorm and PxrDisney really stand out here, simply by the fact that they are modifying the shadow terminator according to the roughness (diffuse roughness for Fstorm, global roughness for PxrDisney). We can also notice that PxrDisney shader brighten up the diffuse at grazing angles, which Fstorm doesn't. Let's try to go a little bit more in depth.

It looks like there are two models that seem to be involved here :
_the diffuse model
_the geometric shadowing-masking model

For the diffuse model, PxrDisney uses a custom-made empirical brdf based on their observation of MERL100 samples.

Quote
This produces a diffuse Fresnel shadow that reduces the incident diffuse reflectance by 0.5 at grazing angles for smooth surfaces and increases the response by up to 2.5 for rough surfaces. This seems to provide a reasonable match to the MERL data and was also found to be artistically pleasing.

This is clearly noticeable on the PxrDisney test. As a contrary, Fstorm doesn't seems to do such computation and I now assume Lambertian model is used there.

The shadow terminator seems to be driven by the geometric shadowing-masking model which represent the shadowing from the microfacets (a.k.a specular G function). The BRDF viewer allows us to preview the different BRDFs independently, to better see the distinct contribution of each function in the shader. I used it to preview some specular G functions and made some screen of the Walter BRDF which is the one that seems to be the closest to what we get in Fstorm.

Min and max :





This function exposes an alphaG parameter which has a range of [0.001;1]. What's more, the PxrDisney has been implemented as follow :

Quote
we use the G derived for GGX by Walter but remap the roughness to reduce the extreme gain for shiny surfaces. Specifically, we linearly scale the original roughness from the [0, 1] range to a reduced range, [0.5, 1], for the purposes of computing G.

This correlates very well with what we get in Fstorm -> diffuse roughness range [0.5;0.99].

However, the implementation of this function seems to differ blithely between the Fstorm shader and Disney shader. In the Disney shader, everything is derived from the global roughness setting and is automatically performed backend. In Fstorm, the parameter is exposed and this seems to affect the diffuse component only.

In regards to the "more directional look" Juraj and Dubcat were talking about, I've also made some test on the specular part :

Corona :



Fstorm :



I guess it's because Fstorm uses Beckmann BRDF instead of GGX :

Beckman :





GGX :



« Last Edit: 2018-02-08, 15:50:20 by Fluss »

2018-02-08, 16:55:25
Reply #152

Fluss

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Oh and just for the sake of it, here is a real photograph. Better than thousand words....


2018-02-09, 02:26:00
Reply #153

dubcat

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damn, you guys have been going ham since my last visit. Big thank you to Fluss for all the testing, really appreciate it! That photo is my staple for render testing!
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2018-02-09, 02:59:08
Reply #154

sebastian___

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Very interesting the real photograph, too bad it has light bouncing from bellow and it's a little harder to compare the lower area, because it's standing on a white plane.

2018-02-09, 03:49:57
Reply #155

worx

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Is there a way to replicate defuse roughness in corona? Because i also find corona being a little flat, and really have to use post to get that soft shading looking

2018-02-09, 09:00:15
Reply #156

nkilar

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Great tests @Fluss ! :) I suppose I am late to the party when it comes to realizing that FStorm uses the Beckmann BRDF model. Huh. Thanks for the tests!

2018-02-10, 17:58:58
Reply #157

Fluss

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Very interesting the real photograph, too bad it has light bouncing from bellow and it's a little harder to compare the lower area, because it's standing on a white plane.

You are right. That and also the fact that the studio setup should produce way softer shadows than the HDRI used in the tests which should greatly influence the shadow terminator on the sphere. I'm gonna reproduce the setup to see how it behaves in Corona.

Anyway, after a lot of testing and observation, I think the diffuse roughness implemented in Fstorm is kind of weird. It shouldn't affect the diffuse that much, plus it does not affect what it is intended to. It gives a kind of coated material effect on every single shader created.

The PxrDisney shader affects both the diffuse at grazing angles and the shadow terminator, and it's much more subtle. BUT we lose control over the diffuse appearance as it's fully automated and there is no parameter exposed. It seems that they realized that since they have backtracked on that particular point. Indeed, the PxrDisney shader is already "outdated" and has been relegated to the legacy tab in the lastest Renderman version. It's still there but only for back-compatibility. They are now using the PxrSurface shader which is much more complex than the Disney one. The diffuse part is now pure Oren-Nayar. And I personally think it's the way to go.

In fact, I think CoronaMtl is not that far from the perfect shader, it just misses some features here and there.

To me, the perfect shader would probably be a carbon copy of the Alsurface shader + some features of the PxrSurface shader. This is what I'd go for :

_Better diffuse model (Oren-Nayar)

_An additional specular lobe. We will then be able to produce proper coated materials. WE NEED THAT. The CoronaLayeredMtl is.. well it's not a layered material, it's a blend material which is not the same. A proper layered material would allow us to stack multiple specular lobes in an energy conservative way, the top layers affecting the ones underneath.
At that point, with these only two features, the CoronaMtl would offer everything the Alsurface shader does. (minus the choice between Beckmann and GGX microfacets distribution).

I'd then add some nice features from the PxrSurface shader. Some of them are available following two modes, artistic/physical. I'd stick with the physical mode only :

_Layer thickness for the clearcoat: Everything is in the name, it simulates thickness for the additional specular lobe, really cool.

_Iridescence

_Fuziness: Full featured with gain, color, cone angle and bump. Not physically accurate but still nice to have

_Bump To Roughness: Insane feature! Basically,  it can use normal, displacement or even bump maps to affect microfacets distribution and anisotropy, in order to recreate surface imperfections in a way that is less prone to diverge according to the distance and produce more physically correct light interaction. (cf. paper below)

You can refer to the renderman documentation for more info on their surface shader: https://rmanwiki.pixar.com/display/REN/PxrSurface

And I strongly recommend you to read their recent paper on their material pipeline, really interesting: http://graphics.pixar.com/library/PxrMaterialsCourse2017/paper.pdf
« Last Edit: 2018-02-11, 17:06:48 by Fluss »

2018-02-14, 11:30:11
Reply #158

johnymrazko

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I was tired of the default material sphere that stretch materials all over the place. Here is a little guide on how to make a good looking material sphere.

Create a GeoSphere 50cm radius, since most scans nowadays are 1 meter.
128+ segments.
Type "Octa"



Throw a "Spherify" on there just to be safe



Add a "UVW Map" "Planer" mode



Default Sphere, nasty



Box turned in to a sphere



GeoSphere with Planar



Hey dubcat

this shader ball works only when viewing from the front right? other views would be distorted if I am applying it correctly

2018-02-17, 12:33:35
Reply #159

Juraj Talcik

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Great testing Fluss !!!

Sadly the issue isn't given much attention. It's all or nothing so currently it's volumetrics, and better shader and post-production will be 2020 I warrant a guess :- )
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2018-02-18, 15:54:41
Reply #160

Fluss

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Hey dubcat

this shader ball works only when viewing from the front right? other views would be distorted if I am applying it correctly

You can try with a simple box, no segments, with UVs -> turbosmooth with multiple iterations -> spherify

Great testing Fluss !!!

Sadly the issue isn't given much attention. It's all or nothing so currently it's volumetrics, and better shader and post-production will be 2020 I warrant a guess :- )

Yes I guess it's not the priority ATM
« Last Edit: 2018-02-18, 16:36:24 by Fluss »

2018-02-20, 17:58:36
Reply #161

dubcat

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Hey dubcat

this shader ball works only when viewing from the front right? other views would be distorted if I am applying it correctly

Hey man! Yes, it's only for Corona Material Thumbnail preview or as a preview for your Material Library.

------------------------------------

I've been taking my Megascans scripts to the next level the past week.
Yesterday I wanted to solve the whole translucency issue. We have a front lit albedo scan and a back lit translucency map scan. There should be no reason why we need to adjust these maps for the material to behave properly. I've solved the issue, and this is how translucency is taken care of in my latest script.

In Corona we have Translucency "Fraction" and "Color.
When Fraction is 0 it's pure diffuse, the material is black when back lit. When Fraction is 1, it's pure Translucency Color when back lit.
Translucency Color gets multiplied by Translucency Fraction.
Currently the script is using 0.5 Fraction to get 50/50. Translucency map is multiplied by 2, since 0.5 * 2 = 1.







As a little side note.
We can't disable IOR with a Corona Color anymore. I noticed this when I was explaining complex IOR.
You can see here that the last 10 degrees are getting darker. 89 degree is 232 RGB.



edit: fixed a typo
« Last Edit: 2018-02-20, 19:58:22 by dubcat »
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2018-02-20, 22:33:10
Reply #162

johnymrazko

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thanks for the reply

regarding megascans, if I would manually tweak the values without script to look correct it is rgb level 2.0 and translucency fraction 0.5 right?

2018-02-20, 23:26:10
Reply #163

oddvisionary

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I just found a LUT converter in the newest official Megascans Bridge version by the way. Might be a bit late in the discussion or you already know it...
Freelance Post-Prod / Lighting & Look Dev 3D Generalist | VFX Designer | Sound Effect Recordist & Sound Designer

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2018-02-21, 00:32:09
Reply #164

dubcat

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regarding megascans, if I would manually tweak the values without script to look correct it is rgb level 2.0 and translucency fraction 0.5 right?
Yep :)

I just found a LUT converter in the newest official Megascans Bridge version by the way. Might be a bit late in the discussion or you already know it...

Hey!
That's my old LUT, it was hand made up to IOR 8 or something like that.
I've attached my latest version that was generated with code, it can remap any RGB value possible :)

edit:
Here is a test render using my improved IOR LUT.

« Last Edit: 2018-02-21, 01:34:41 by dubcat »
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2018-02-27, 01:39:40
Reply #165

dubcat

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2018-03-06, 15:58:48
Reply #166

dubcat

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I found a little hack to emulate how light get whiter in Corona.
We don't get that nice ACES color tint, but it's better than not having the effect.

Default Corona



My new VFB ACES emulation



Default Corona - Yellow Sun "bug"



Fix



I've attached the new settings file.
You only have to adjust exposure to your liking.

But stupid hacks like this wont be necessary if we get proper custom matrix.

Edit Edit:
Added v3 that is "Sun proof".
« Last Edit: 2018-03-06, 23:00:03 by dubcat »
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2018-03-06, 18:23:03
Reply #167

vemod

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Or we could just make a stupid hack it at the light source instead :)

No perceptual color difference when viewed at regular exposure but it gets the "correct" overexposure behaviour.
I couldn't be arsed to replicate the grid completely, but you guys get the point.

Photoshop borked the colors as well, so try it with the supplied HDR values in a corona color that you plug in to the texture slot of a light.

It's generally a good idea to stay away from pure colors in CGI even when it comes to lights it seems :)

2018-03-09, 01:58:26
Reply #168

dubcat

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To be honest I can't remember if I have posted this before, but people have been asking for it.
I have included my "Apply Image" script that makes a 1:1 highpass of your texture. This can be used on any texture, I mostly use it on diffuse and glossiness to make real time adjustments in Corona.

All the blending modes are in sRGB! (Something that is Corona exclusive for now!)

Open your texture map in Photoshop and run my attached script.
You will get this result.

Hide the bottom layer "albedo color" and save the "apply image high pass" map as a png or tiff.



Create a setup like this, where you sample the bottom layer as "Albedo" color.



You can make a glossiness variant like this
But I usually normalize my glossiness map in Photoshop.



Just remember that normal materials does not go bellow 0.4 glossiness. It is great that we have the opportunity to go down to 0. But just keep in mind that everything bellow 0.4 is for special occasions. If you have to fake depth, use an IOR map (Reflection Level clamp your IOR).
If you don't understand how how reflection level work, think of it like this. You have a black background layer in Photoshop, you have your IOR as a white layer above. If you reduce the "reflection level", its like you are reducing the opacity of the white layer in Photoshop. 89 degree will never be white!
« Last Edit: 2018-03-09, 04:21:08 by dubcat »
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2018-03-09, 11:05:19
Reply #169

romullus

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Thanks a ton for you invaluable input to community dubcat!

I have a question about IOR map. What would be correct way to obtain such map? Let's say if i'd invert height/displacement map and ajust levels, so majority of colours would be at 170 RGB and cracks/identations would be white, approaching 255 RGB, would that make good IOR map?
I'm not Corona Team member. Everything i say, is my personal opinion only.

2018-03-10, 21:55:40
Reply #170

dubcat

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Hey

You have to make an AO map from your Normal map. There are multiple bakers out there that support normal map.

Substance Designer Baker with default settings.



Substance Designer Node with default settings.



Quixel dDO with default settings.



I'm sharing my AO to Specular action.
I have split the action into 3 parts, so I can tweak values. No AO map is the same.
Remember to run them in the correct order!



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2018-03-11, 14:50:22
Reply #171

A515

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2018-03-13, 09:21:31
Reply #172

dubcat

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I had a dream last night, I made a new IOR map generator. It supported IOR up to 1.8. So if you scanned a concrete wall or asphalt, the small stones would get higher IOR then 1.5.
If you have cross polarized a composition material before, you know what I'm talking about.
So the first thing I did today after some coffee, was to remake that generator, and it has basically changed the way I create PBR textures.

Here are some reflection tests

No IOR Map



Official Megascans Specular Map converted to IOR



My new Generator.
You might notice the gem stones in the asphalt, and you can see how everything looks more defined and crisp.
It basically looks like a real cross polarized specular photo.

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2018-03-13, 09:45:15
Reply #173

WAcky

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Love seeing this thread progressing. Dubcat thank you for all the work. Do you have any recommended reading on getting started with creating one's own scanned materials? IE polarized lights/filters etc etc?

Cheers!

- James

2018-03-13, 10:14:26
Reply #174

dubcat

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Do you have any recommended reading on getting started with creating one's own scanned materials?

Hey!

https://www.allegorithmic.com/blog/your-smartphone-material-scanner is a great starter guide.
They don't cover cross polarization. But if I remember correct, I made a how to on the forums somewhere.

You basically mount a linear polarizer sheet to your camera and light. Shot once, rotate the polarizer sheet on your light 90 degree, shot again.
One of the pictures contain "50% diffuse" and the other contains 100% specular + 50% diffuse.
Open both photos in Photoshop, convert to 32 bit mode (Need 32bit for correct linear math).
Subtract the "50% diffuse" photo from the "100% specular + 50% diffuse" photo, this is your spec map.
Take the "50% diffuse" photo and add it with itself once, this is your 100% diffuse map.

Repeat this process on all 4 angles, you end up with a nice albedo map and a glossiness map.
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2018-03-13, 10:36:00
Reply #175

Fluss

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Nice stuff Dubcat, as always !

2018-03-13, 13:16:03
Reply #176

WAcky

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Magnificent. Thank you!

Do you have any recommended reading on getting started with creating one's own scanned materials?

Hey!

https://www.allegorithmic.com/blog/your-smartphone-material-scanner is a great starter guide.
They don't cover cross polarization. But if I remember correct, I made a how to on the forums somewhere.

You basically mount a linear polarizer sheet to your camera and light. Shot once, rotate the polarizer sheet on your light 90 degree, shot again.
One of the pictures contain "50% diffuse" and the other contains 100% specular + 50% diffuse.
Open both photos in Photoshop, convert to 32 bit mode (Need 32bit for correct linear math).
Subtract the "50% diffuse" photo from the "100% specular + 50% diffuse" photo, this is your spec map.
Take the "50% diffuse" photo and add it with itself once, this is your 100% diffuse map.

Repeat this process on all 4 angles, you end up with a nice albedo map and a glossiness map.

2018-03-13, 17:20:09
Reply #177

dubcat

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The new IOR generator is almost complete, this will be the final rev for today.

No IOR map



Old Specular to IOR map



New IOR Generator

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2018-03-13, 17:22:06
Reply #178

fabio81

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Dubcat can I ask you something ?
do you usually apply the lut file to a 32bit or 16bit file? because I noticed that Corona when applying the lut is as if it added a gamma 2.2 and then applies the lut above.
Now I do not know if programs like nuke or fusion should do the same thing or apply the lut directly above the 32bit.
how do you do with Nuke or Corona?

thanks!

2018-03-13, 17:51:36
Reply #179

dubcat

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do you usually apply the lut file to a 32bit or 16bit file?

Hey!

If you are using Photoshop, convert the specular map to 16bit and apply the LUT. Load the bitmap as gamma 1.0

If you want to do everything inside 3dsmax, you have to load the specular map as gamma 1.0, use a ColorCorrection map to convert it to Linear, because of 3dsmaxs gamma mess. Apply the LUT, and convert it back to sRGB.



The new IOR generator is not a LUT. You can feed it scanned specular maps or old reflection level maps.
Will make a separate post on how to use it when it's ready.
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2018-03-13, 17:59:22
Reply #180

fabio81

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thank you so much!

2018-03-16, 17:07:33
Reply #181

dubcat

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The new generator is almost complete.
It can generate IOR and Specular maps from 3 different map inputs so far.

#1 Cross Polarization Specular Scan
This is the best solution, your Corona render will have identical reflections to the real world cross polarized specular map.

This is the result



#2 Normal Map
This is the second best solution. If you don't have a cross polarized specular map, you can use this one.
You can use any existing normal map. It will generate a IOR / Specular map based on the normal map height strength.
This was initially Jurajs idea, and Ondra gave me some pro tips. So this generator would not exist if not for them!

This is the result



#3 Reflection Level
This is the shittiest last solution.
It will convert old reflection level maps to IOR/Specular. This will give you the same look as you had before, but it will not clamp fresnel.

Since the new generator also generate specular maps, we get real world reflection behavior in Unreal 4!



When everything is road tested and tweaked, I will compile them as 3 LUTs.
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2018-03-16, 23:02:16
Reply #182

dubcat

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Thought I could share my custom metal settings. It's nice to get the correct scanned behavior from "refractiveindex.info", but the color values are way off. These are my current reference matched metal materials, these change every week, so it's more of a snapshot of my current settings.



















Gold Example:

« Last Edit: 2018-03-16, 23:05:37 by dubcat »
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2018-03-20, 05:08:32
Reply #183

Basshunter

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Hi @Dubcat, very interesting topic. So, this "Specular map" would be used as Glossiness map right? And reflection slot full white?

2018-03-21, 16:27:28
Reply #184

dubcat

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"Specular map" would be used as Glossiness map right? And reflection slot full white?

Hey!
The IOR map is used in the "Fresnel IOR" slot and complements the glossiness map. They are both generated from the same cross polarized set of pictures.
Current PBR shaders can't emulate real world materials with just albedo/glossiness.
If you build a virtual material scanner inside Corona and scan your materials, you will see that the cross polarized specular does not represent real world at all.
My new IOR generator takes care of this problem.

Here are some examples from my last virtual 3d scanner test.

This is how I generate my maps



No IOR map Specular



IOR map Speulcar


Glossiness map generated from the material with no IOR Map



Glossiness map generated from the material with IOR Map

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2018-03-21, 23:10:41
Reply #185

mferster

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If you build a virtual material scanner inside Corona and scan your materials, you will see that the cross polarized specular does not represent real world at all.

Wait, wait, wait! How did you simulate a cross polarization filter material in corona?

2018-03-22, 09:25:46
Reply #186

karnak

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@mferster

In Corona you don't need cross polarization to split diffuse reflection from specular reflection. You have render elements for that.
Conversely, in real-world you need cross polarization because your capture equipment (i.e. your camera) most likely won't have render elements. :D

I think dubcat is saying that when you compare the render element to the real-world cross-polarized photo, the two don't match at all.
He is using a method for processing scanned data, but looks like the inputs in his test are from Corona so he can iterate and change things faster.
Corona Academy (May 2017)

2018-03-22, 09:33:52
Reply #187

Fluss

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Looks great Dubcat! Some questions comes to my mind:

How can you extract specular values from a normal map?
I guess you basically linearly remap the "height" infos of the normal map, keeping the reflectance between the 2-5% range at F(0°), but that way, I can't understand how it can be better than a map derived from a reflection map which contains "proper" lighting pieces of information compared to a normal map.

Reflection and Specular maps are sRGB bitmaps (gamma 2.2) while normal maps and IOR maps are Linear (gamma 1.0), How is that handled?

Hey!
The IOR map is used in the "Fresnel IOR" slot and complements the glossiness map.

I a bit confused on the difference between IOR and Fresnel IOR inputs. Can you explain what properties are defined by each of those?

2018-03-22, 16:03:41
Reply #188

mferster

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@karnak

Yes, I am aware of how render elements work, thanks karnak. It looks like I misinterpreted what he wrote and got excited at the idea of simulated cross polarization filters.

2018-03-22, 17:16:56
Reply #189

karnak

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That was just my interpretation of what he wrote, and I hope I didn't accidentally offend you with it. :)
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2018-03-22, 18:18:15
Reply #190

mferster

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It's all good, I think you are quite right, that is indeed what he is doing.

But now it has lead me down a rabbit hole of experimentation to see if it is actually possible to simulate cross polarizing filters in Corona (or fake it atleast).
« Last Edit: 2018-03-22, 18:22:45 by mferster »

2018-03-22, 19:45:50
Reply #191

karnak

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Me too and I'm also excited about OSL in 3dsmax2019. A lot of stuff to experiment with! :D
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2018-03-23, 00:46:54
Reply #192

dubcat

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Wait, wait, wait!

Hey!
Create a "CShading_Components" pass and disable "Indirect". This should give you the same result as we get from cross polarizing and subtracting.
When we capture materials in real life, we use fast shutter speeds like 1/400+ to kill ambient light. We only want the direct flash/softbox light.

How can you extract specular values from a normal map?
I guess you basically linearly remap the "height" infos of the normal map, keeping the reflectance between the 2-5% range at F(0°), but that way, I can't understand how it can be better than a map derived from a reflection map which contains "proper" lighting pieces of information compared to a normal map.

Reflection and Specular maps are sRGB bitmaps (gamma 2.2) while normal maps and IOR maps are Linear (gamma 1.0), How is that handled?
Hey!
You are pretty much spot on.
In a perfect world we generate a 4+ point specular scan of a material, and run it through my generator. I only do Arch Viz and 80% of my texture library is still old school "non scanned".
By extracting height data from old school normal maps, we can at least fake depth somewhat. It's still better then not having any depth emulation at all.
And as a last resort, we can convert old reflection maps to IOR. This can be nice for wood materials, where we have to emulate the wood tubes that go in different directions. When we don't have a specular/normal map, and we don't want to use "Reflection Level" to clamp the Fresnel. "Reflection Level" is pure evil! (As a side note, pleeeeeeeeaaaase Ondra, can we get a Wood Material ?, http://www.cs.cornell.edu/~srm/publications/SG05-wood.pdf)

I a bit confused on the difference between IOR and Fresnel IOR inputs. Can you explain what properties are defined by each of those?
To be honest I have never done any research if the "Refraction IOR" behaves differently from "Diffuse IOR" in Corona, they should be the same. Most engines only have one IOR that control both diffuse and refraction.

---------------------------------------------------------------------------------------------------------------

Every now and then I get PMs from people that are really interested in materials and CG in general.
I use my Skype at work, so I can't add everyone there.
I've made a new Discord server that will be invite only, but everyone can join.
Send me a PM, and I will send you an invite.
« Last Edit: 2018-03-27, 01:20:03 by dubcat »
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2018-03-28, 17:22:02
Reply #193

Basshunter

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Hi @dubcat. I recently discovered this thread and I must say everything that has been talked here is SO interesting! However, as a new Corona user I feel a little lost when trying to find the beginning and conclusion of the topics. Is there any way to easy access files, pictures or written conclusions resulting from the topics treated? Maybe another thread?
« Last Edit: 2018-03-29, 07:15:04 by Basshunter »

2018-03-31, 23:51:42
Reply #194

dubcat

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Hi @dubcat. I recently discovered this thread and I must say everything that has been talked here is SO interesting! However, as a new Corona user I feel a little lost when trying to find the beginning and conclusion of the topics. Is there any way to easy access files, pictures or written conclusions resulting from the topics treated? Maybe another thread?

Hey!

I will consolidate everything here http://dubcats-secret-little-hideout.wikia.com/wiki/Dubcats_secret_little_hideout_Wiki, it will take some time before the wiki gets refined and contain everything.
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2018-04-11, 15:33:15
Reply #195

dubcat

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Paint manufacturers "fake" the brightness of darker colors on swatches. Luckily we can get measured "Light Reflectance Value" of the actual paint online.
The swatches also include IOR from what I understand.

Juraj sparked some ideas in my head yesterday, and last night I had a dream where I made a LUT that convert swatches to albedo.
The LUT will remove fake brightness and IOR from the swatches.
The more color samples I have, the more accurate the LUT will be.

I will share the LUT when it has at least 100 swatches, and then keep posting updates as I add more colors.

Here is an example of what it will do

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2018-04-11, 18:15:12
Reply #196

peterguthrie

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2018-04-11, 18:33:14
Reply #197

mferster

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Dubcat's dreams are the best dreams. I wish my dreams were as productive.

*edit: So on a general bases what's the translatable value from a swatches Light Reflectance Value to a material's Albedo or IOR?
« Last Edit: 2018-04-11, 19:50:14 by mferster »

2018-04-11, 18:52:36
Reply #198

Dippndots

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Where did you get these swatches from originally dubcat? Color picking from manufactures' websites?

2018-04-11, 21:09:11
Reply #199

dubcat

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I love your dreams dubcat :)

hehe :)

So on a general bases what's the translatable value from a swatches Light Reflectance Value to a material's Albedo or IOR?

+

Where did you get these swatches from originally dubcat? Color picking from manufactures' websites?

Most painters in Norway use Jotun, so I sample my colors there.
They have a new 2018 set, that sparked the whole conversation with Juraj and Daniel R.
I can do a quick example. Lets use a dark color, since bright colors swatches are pretty accurate, we only need to remove 4% IOR from bright values.

Lets say someone want this dark brown NORWEGIAN WOOD 10981

You sample the manufacturers value



This color is #7f5c47

We go to e-paint and search for #7f5c47, because we don't know what the international standard name is.
The search result tell us that this color is part of "AMS Standard 595A -  Brown international"
And that the scanned LRV aka "Light Reflectance Value" is 13% Linear.

We can try to check the LRV of our current sampled value. But if we disable sRGB in "Corona Color Picker", we still get sRGB "Value" in Corona. I have made a requested that "Value" should be affected by the sRGB toggle, but I don't think it will happen. Maybe if enough people bug the devs about it, we can get this feature. It's really important.



Since "Corona Color Picker" "Value" is not linear, we have to do some side stepping.

Disable "sRGB", go to "0-100%", input 13.



Enable "sRGB" again and go back to "0-255".



Copy the Red value in this case 101.

Go back to our sampled color, and paste 101 into "Value"



We have now converted this preview swatch into real world LRV. But from my understanding this value still contain 4% reflectance from IOR 1.5.
But really, no one will notice this 4%. But I can't sleep well at night, knowing that I apply IOR 1.5 twice. And this is why you are one step ahead og the rest.

This is where I use pure white in "Environment Background", create a plane. Look straight down at the plane in orthographic. Use 1.5 IOR and 1 Glossiness (GGX glossiness will mess this up, if you use anything bellow 1). Then adjust "Value" until the sRGB match the original corona color value.

In our current case, this is what we get in IR with the corrected sampled color.



The brightest color is 113 sRGB. Because we have to deal with IOR.

But the brightest color in our sample is 101 sRGB, and these guys have to deal with IOR in real life too.

So we have to adjust our sample down to 87, 64 ,50.



Sometimes the darker colors change hue and saturation when you do drastic changed like this, you can manually correct this. But my LUT will take care of all this mess. The LUT is not generated in sRGB space.

TLDR; Just remember to give the devs a little PM that you want the sRGB toggle to affect "Value" in "Corona Color Picker", features like this depend on you!
« Last Edit: 2018-04-12, 17:00:05 by dubcat »
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2018-05-22, 14:40:57
Reply #200

IsmaeL

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This is exactly the stuff I dream about XD

Just made a bathroom furniture catalogue and color is a major issue. The client uses NCS and we had to adjust everything in Post to match print and swatches. Just horribly painful.
So I'm glad to see I'm not the only one annoyed by the Corona Color Picker.

It would be so nice if we could get the Cinema Color Picker, it is very elaborate and useful.

Talking about color, maybe we could ask the devs to automatically load the screen color profile into the Corona Frame Buffer. Because right now calibrating my screen is not very useful in Corona.
Falling in love with Corona

2018-07-06, 02:53:11
Reply #201

dubcat

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I was having a chat earlier this year about HDRi and Corona Sun/Sky. Theres been lots of stuff happening in RL, so I haven't had much time to be active online (both forum and discord). I thought this stuff might be interesting for some people, so lets recap.

I made the switch from Vray to Corona back in 2015, and one of the first things I noticed was that everything felt "orange". I'm talking about VFB 6500K white balance.
I can't express how good it was to drop that damn green vray usb dongle that kept disconnecting every 10 min, sometimes mid render.

Earlier this year, people were going crazy on social media about HDRi, how good HDRi light was. They said stuff like, if you want smooth shadows, you must use a HDRi.

So earlier this year, I wanted to answer two questions. Why do I feel Corona is orange, and why do 90% of the world prefer HDRi skies.

I live in Scandinavia and I know that the strongest sun is at 12:00 6/21/2018. This gives us a latitude of 59.917.
The closest HDRi I could find online was Peter Guthries 1216 Sun Sky which is 58 degree.

Peter has been a good boy and updated his skies with a calibrated sun, but I wanted to keep the original camera sun values. So I will be using the original HDRi which he also provide.

Peters 1216 Sun sky is pretty much perfect, but as with any real world HDRi captures, there will be sun flare. We have to isolate the sun from the sky. And the sky has to be isolated from the sun flare.

We have to base our test on something, or else it would be random values. As usual I will be using 18% grey on my test subjects, this is 117 sRGB. Corona sun will be matching Peters HDRi angle, about 58 degree. Corona sky is a dynamic map, it will change color and gradient based on the sun position. We will change "Horizon blur" to 0 and Ground "color" to black, to match Peters HDRi.

The first thing we have to do is calibrate our "camera" aka VFB. We are using Corona Sun and Sky with default settings.
We know our test subject is 18% grey aka 117 sRGB. We have to lower EV in VFB to -5.24 for our test subject to meet 117 sRGB.
-5.24 EV will be our base for the rest of this test.



Our next step is to isolate the Sun from the HDRi, I will do this inside 3dsmax with this mask.



When we isolate the sun from the sky, this is what we get. Remember that this is the original camera capture. Peter provides a calibrated sun version when you purchase the HDRi. Most companies will only provide the "Photoshoped" perfect version, but Peter is keeping it real. If your monitor is not calibrated, it will show up as black.



If we boost the HDRi "RGB Level" to 520, we will match our calibrated Corona Sun value.




This calibration phase has to be done with any HDRi. It doesn't matter if its CG-Source, PG Skies or anyone else. No real world commercial camera can capture the real world sun value in a HDRi. Most people use the 0.8 gamma trick, this trick will boost your sun value a tad bit, and mess your sky values up like there is no tomorrow! The best way to handle real world HDRis, is to isolate the sun from the sky and calibrate them separately, because the values are so far apart.

I've been splitting sun/sky on a bunch of real world HDRis and on average the sky is "the sun RGB Level" / 100. In our case that is 520 / 100 RGB = 5.2 RGB.

I had to mask the sun flares on this render to calculate the values.



We have our Peter Sun/Sky split and calibrated. It's time to match Corona Sun/Sky to our real world captured data.
Lets start with the sun.

Our first goal is to match the "softness of the sun", 2.5 Corona sun size does the trick.
Our next goal is to match the RGB. When we switch to "Direct Input" aka 1.0 White Sun. 1 sun intensity does not give us 1 intensity in the render. So we have to boost the Sun intensity to 1.12 (Corona error?).
To match the sun RGB we have to change Red to 254 and Blue to 252.



This is what we get if we just isolate the sun from the HDRi and do not remove the lens flare. It's kind of crazy how much lens flare affect the render. Since lens flares have much lower value than the sun, it will help generate smoother shadows. So maybe I judged those social media people too soon.



If we remove the lens flares, we get this from the HDRi. You can see all the direct shadows from the lens flare is gone.
This is what we base our Corona Sky on.



To get a close match we have to use "Turbidity" 1.7 (1.7 does not satisfy the Peter capture, maybe 1.5 would, but we can't try)  and these values inside a "Color Correction". Color Correction is linear so 1 * 2 would result in 2.



This is how Peter Guthries 1216 Sun looks calibrated



With our quick approximated values, Corona Sun/Sky looks like this.



So in the end. Even small lens flares from real world captured skies will give you more "detailed" skies. Since you mix the sun with less valued light sources. If you capture a sky with clouds, the clouds will in most cases go above +1 RGB. Resulting in more soft light sources.
Most HDRis will have white balanced suns. But if you use Corona Sun "Realistic" it will give you an "Orange" look.
« Last Edit: 2018-07-06, 05:15:38 by dubcat »
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2018-07-06, 03:52:02
Reply #202

arqrenderz

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Just WOW to the last dubcat post, you know a lot of this.
Where can u normal user start, in order to better understand all this concepts?

2018-07-06, 11:11:55
Reply #203

piotrus3333

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finally. thx for educating people about flares on hdris.
another thanks for all of you guys chasing fstorms tone mapping. great work. I'm spending more and more time on this forum because of content like that.

quick question about paint color samples: why subtract 4% form 13% LRV when corona's mat does energy conservation for you?
and what about doing it with composite map from max? (attached). 13% gray map and color sample on top in "color" blend mode plus maybe lowering saturation a bit in some cases (oversaturated samples made looking nice on screens)

2018-07-06, 11:34:41
Reply #204

johan belmans

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2018-07-06, 12:36:51
Reply #205

Juraj Talcik

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quick question about paint color samples: why subtract 4% form 13% LRV when corona's mat does energy conservation for you?

I have found this to be very arbitrary ad-hoc introduced in Corona shader. It was done long time ago as quick-fix for people over-doing bright albedo.
It's not part of the energy conservation model but additional part on top. Perhaps the devs could show what exactly it does because I haven't found it to correlate with 4perc (the most common base reflectance of insulator).
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2018-07-06, 13:12:56
Reply #206

piotrus3333

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4% or 24% does not matter as long as diffused reflections are dimmed by direct ones. that looks ok to me in Corona but I also never bothered with side-by-sides.

2018-07-06, 15:04:08
Reply #207

karnak

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Let's say that the color was sampled with a spectrophotometer. What you get from that instrument is one reflectance value that contains both diffuse and reflection (with no distinction). So, if you want only the diffuse you have to know the reflection value and subtract it from the value the instrument gave you.

When you read that you have to subtract 4%, it's because they assume the color was sampled from a non-metal surface with the default 1.52 IOR (that at normal incidence equals 4%).
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2018-07-06, 15:29:08
Reply #208

piotrus3333

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correct me if Im wrong but „Diffuse” in corona mat describes total reflectance (diff + direct). when you add „Reflection” on top of that Corona dimms diffuse part to balance the energy.

2018-07-06, 15:40:22
Reply #209

piotrus3333

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...dimms „Diffuse” part to balance the energy.

2018-07-06, 17:08:48
Reply #210

Juraj Talcik

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correct me if Im wrong but „Diffuse” in corona mat describes total reflectance (diff + direct). when you add „Reflection” on top of that Corona dimms diffuse part to balance the energy.

No, the Diffuse in CoronaMTL is only the diffuse albedo part, not total albedo (Diffuse reflection albedo+ Specular reflection albedo). Second part is correct about Energy Preservation.

But energy preservation in shader doesn't account for scanned F0 values. There is some arbitrary deduction from early version ( two years ago ?) done on diffuse but this is done on top and it's just hack.
It does basically the same thing, reducing the diffuse albedo slightly even before specular is applied. The amount is smaller than 4perc. though.

Same goes for using photometric stereo scanned textures. Energy preservation will only kick afterwards but for the shader to recreate exact albedo you need to feed the diffuse slot only pure 100perc. diffuse albedo.
( additional cross-polarization scan to extract specular scan and then the classic 50perc. negation to get pure diffuse albedo).
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2018-07-06, 18:24:00
Reply #211

piotrus3333

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all clear, thank you.

2018-07-08, 02:22:05
Reply #212

dubcat

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what about doing it with composite map from max? (attached). 13% gray map and color sample on top in "color" blend mode plus maybe lowering saturation a bit in some cases (oversaturated samples made looking nice on screens)
Hey man!

I've tried to do this procedure in RGB, but it's just not possible. Paint companies just love to boost those dark colors in their previews, and keep the bright colors somewhat correct to the LRV.
My workflow is to calibrate as much as I can to a color checker, and use real world light values. This gives me a dull and boring raw render with bright burning light spots. My post settings give these ugly raw renders the "larger than life" feeling. This is just my workflow though, I'm not hating on people who like to get good results with raw renders.

The reason I use 1 filmic HC in my ACES VFB hack is because filmic make our max white 255 RGB. We exploit this with our standard Corona HC setting, and reduce it bellow 1. This will boost our whites and give us that nice pop.

Juraj and karnak has been nice and answered all the 4% IOR questions :)
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2018-07-12, 04:51:24
Reply #213

dubcat

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At some point in your archviz career, someone will request a cross fit machine in their render. I had this terrible experience back in 2014.
The elephant in the room is the hybrid metallic paint. How do you deal with it ?

The reason I want to mention this, is because I had to relive my 2014 nightmare a couple of weeks ago. We could counter this problem with metalness workflow. Chaosgroup has already implemented this workflow in Vray Next.

In our current situation you want to make a material like this. This could be done in one map if we had metalness, and we could discard the falloff map.





edit:

The kind of noise you want to use.



Red is plastic and green is metallic

« Last Edit: 2018-07-12, 19:46:49 by dubcat »
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2018-07-12, 09:38:40
Reply #214

IsmaeL

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Interesting material. Looks very nice.
I thought it's just paint with a higher IOR but never had to make this one before so my opinion doesn't count XD

What does  the metalness map look like. I seams just white.
Falling in love with Corona

2018-07-12, 19:48:26
Reply #215

dubcat

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What does  the metalness map look like. I seams just white.

Hey man
Updated the post with noise samples.
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2018-07-13, 14:05:29
Reply #216

maru

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You can map Fresnel IOR so wouldn't it be possible to make this with just a single material?

2018-07-13, 14:24:15
Reply #217

Jpjapers

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Could you show an example of the material youre recreating?

2018-07-13, 14:29:21
Reply #218

Fluss

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You can map Fresnel IOR so wouldn't it be possible to make this with just a single material?
Yes, I would have done it that way. I don't really like the pure metalness workflow tbh, metallic IOR is not exposed and that's a no-go for me. I just hate the Hardcoded stuff!

2018-07-13, 19:47:30
Reply #219

Njen

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You can map Fresnel IOR so wouldn't it be possible to make this with just a single material?

As long as you are able to treat the dielectric and metallic surfaces differently with the same mask in regards to reflection and diffuse colour it is theoretically possible. But it's just easier to do it with two materials because there would be less nodes to use (less mixes).
Please support my Kickstarter for my animated film, Cyan Eyed (rendered in Corona)!

2018-07-13, 20:23:46
Reply #220

dubcat

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You can map Fresnel IOR so wouldn't it be possible to make this with just a single material?

Hey!

Everything is possible with enough maps.
In this case we have metal flake bits that range from fully covered in paint to not covered at all.
It was easier to control the paint coverage by blending the materials together with random noise values.

Could you show an example of the material youre recreating?

Hey!

It's this type of paint.
If you cross polarize the material, you will notice white spots (metal) in the specular map.
I made the noise size larger in the preview material to make the effect more noticeable.




I don't really like the pure metalness workflow

Hey!

I don't like pure metalness workflow either.
Vray has a really nice implementation. Metalness is 0 by default, no one will notice it's there.
But if we need it, we can change it to 1. Win win.



As long as you are able to treat the dielectric and metallic surfaces differently with the same mask in regards to reflection and diffuse colour it is theoretically possible. But it's just easier to do it with two materials because there would be less nodes to use (less mixes).

Right on!
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2018-07-14, 15:34:34
Reply #221

dubcat

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Here's the first public "Roughness to IOR" LUT test.

Since slate and LUTs are a complete gamma mess, I have embedded all the gamma conversion stuff inside the LUT.

How to:
01. Open the roughness map in Photoshop.
02. Run my high pass action script. This script uses "Apply Image" to generate a perfect 1:1 High pass. It does not use the terrible Photoshop radius based High pass.
03. Load the map inside 3dsMax with "Auto Gamma".
04. Plug the map into "Corona Color Correct" and load the LUT.
05. Plug "Corona Color Correct" into "Fresnel IOR".



Examples, best enjoyed in a new tab.





I have made a High pass filter inside Corona, when I get around to code the new Bridge scripts, you won't even have to deal with Photoshop. In an ideal situation we would get a high pass Corona map, since it's a must when it comes to scanned textures.
« Last Edit: 2018-07-15, 03:55:20 by dubcat »
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2018-07-16, 04:03:41
Reply #222

Basshunter

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Here's the first public "Roughness to IOR" LUT test.

Hi Dubcat,

will you add this info to the Wiki site? It'd be easier to understand for people who haven't followed this from the beginning (Me included)

Thanks for all your knowledge.
« Last Edit: 2018-07-16, 05:26:24 by Basshunter »

2018-07-16, 10:20:31
Reply #223

Jpjapers

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Quote
Hey!

It's this type of paint.
If you cross polarize the material, you will notice white spots (metal) in the specular map.
I made the noise size larger in the preview material to make the effect more noticeable.




Ah right that kind of plastic dipped metal stuff?

2018-07-21, 22:31:04
Reply #224

dubcat

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will you add this info to the Wiki site? It'd be easier to understand for people who haven't followed this from the beginning (Me included)
Of course, I will add it to my todo list :)

Ah right that kind of plastic dipped metal stuff?
Yes something like that :)

------------------------------------

I will be dumping Camera Profiles until the sun comes up today.
Here is a dump of Phase One - IQ3 100MP it "only" cost 50 000$.
I would recommend that you use "Filmic Highlights" 1 as a starting point when using Camera Profile dumps. And then season to taste, because "Filmic Highlights" at 1 will remove everything called highlight. So either reduce "Filmic Highlights" OR if you want to boost the highlights a little, reduce "Highlight Compress" bellow 1, but this will also add contrast. Keep that in mind.

OR everyone could request ACES with at least five parameters:
Slope           - Controls the overall curvature strength.
Toe              - Controls the bottom half of the curve.
Shoulder      - Controls the top half of the curve.
Black Clip     - Moves the left anchor point below 0.
White Clip    - Moves the right anchor point above 1.

But stuff like this only exist in my dreams and Unreal 4.

edit:
So I have dumped a few cameras now, ranging from expensive mobiles, "cheap" cameras to expensive cameras.
Mobiles and "cheap" cameras have a tendency to crunch blacks and boost saturation. While expensive cameras tend to desaturate a little and keep the black crunch to a minimum.
All the devices boost mid/high, and in most cases the center point of the curve is shifted to the left (What Camera Raw 9.9 2010 has been doing all along). 32bit support has been dismissed by Adobe, so RIP 32bit Camera Raw. GG Adobe!

------------------------------------

Waiting for the 18% grey paint to dry.

« Last Edit: 2018-07-22, 02:51:20 by dubcat »
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2018-07-23, 21:29:02
Reply #225

aldola

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2018-07-23, 21:47:57
Reply #226

aldola

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2018-07-23, 23:44:51
Reply #227

dubcat

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give me a canon 5ds :p

Here is Canon 5DS RGB dump. I'm currently not 100% satisfied with my HSL dumper, will hopefully fix it next weekend.
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2018-07-24, 00:08:33
Reply #228

aldola

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2018-07-24, 15:41:51
Reply #229

aldola

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here is a test with the 5ds dump, this is the correct way to use them? may be the higlights are too strong

2018-07-24, 16:08:47
Reply #230

fabio81

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wow! very beautiful the LUT of the Canon 5dS!

2018-07-24, 17:39:14
Reply #231

dubcat

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here is a test with the 5ds dump, this is the correct way to use them? may be the higlights are too strong

I did a quick comparison against default ACES.
You have to use "Highlight Compress" 2.5 and "Filmic Highlights" 1 to match default ACES.
So leave "Filmic Highlights" at 1 and adjust "Highlight Compress" from 2.5 to taste.

edit:

I forgot to say that these settings only count for the Canon 5DS dump.
« Last Edit: 2018-07-25, 05:31:11 by dubcat »
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2018-07-25, 14:07:51
Reply #232

johnymrazko

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Hi dubcat

regarding calibrating hdris - is it neccesary to do even if I use separate light source (Corona Sun) for direct light? - for example noemotion hdris have no shadows from the sun

2018-07-25, 15:44:31
Reply #233

aldola

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Hi, i use this 

https://3dcollective.es/producto/hdri-22pack-pro/


 i think the best quality on the market, no strange tint on the colors and the have very good dinamic range.

2018-07-25, 19:44:01
Reply #234

dubcat

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regarding calibrating hdris - is it neccesary to do even if I use separate light source (Corona Sun) for direct light? - for example noemotion hdris have no shadows from the sun

Hey!

I would still adjust RGB Level to match Corona Sky values at least. Corona Sun will eat all the sky light from those low exposure HDRis.
And just to be sure, I would remove the low level sun. It will only get stronger if you adjust RGB Level.

If we combine Corona Sun and this NoEmotion HDRi without increasing the RGB Level, we won't even notice the HDRi.



If we do a quick sky calibration like this.




We can finally see the HDRi again.





------------------------------------------------------

I had a quick look at the free sample 3DCollective HDRi.

Looks like someone painted the sun with a large soft brush.
The sun value is 1079 times dimmer then Corona Sun.



Here is Corona Sun for size comparison



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2018-07-25, 20:55:35
Reply #235

Njen

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A general rule of thumb when processing HDRI's, or using something downloaded from the internet, it is important to know that at the equator, at 12pm noon, the sun is roughly 100,000 brighter than the average area of a large patch of sky. So as the sun gets lower in the horizon, the brightness of the sun decreases just a little because light has to travel through more atmosphere. And if there is any form of high level cirrus cloud, the brightness is decreased a tiny bit more too.
Please support my Kickstarter for my animated film, Cyan Eyed (rendered in Corona)!

2018-07-25, 21:13:22
Reply #236

aldola

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They are calibrated to use with the camera so 3DCollective_HDRi_022_1722_+8_4K the +8 means that you have to give +8 rgb  output amount to give the correct intensity, this one is a cloudy sky, the sunny ones have a +32 output value.

i dont know if they are correct but they give some nice shadows with the sun.

Adan martin  the creator is on the forum, so i think he can give a more correct explanation

2018-07-25, 21:32:51
Reply #237

johnymrazko

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regarding calibrating hdris - is it neccesary to do even if I use separate light source (Corona Sun) for direct light? - for example noemotion hdris have no shadows from the sun

Hey!

I would still adjust RGB Level to match Corona Sky values at least. Corona Sun will eat all the sky light from those low exposure HDRis.
And just to be sure, I would remove the low level sun. It will only get stronger if you adjust RGB Level.

If we combine Corona Sun and this NoEmotion HDRi without increasing the RGB Level, we won't even notice the HDRi.



If we do a quick sky calibration like this.




We can finally see the HDRi again.





------------------------------------------------------

I had a quick look at the free sample 3DCollective HDRi.

Looks like someone painted the sun with a large soft brush.
The sun value is 1079 times dimmer then Corona Sun.



Here is Corona Sun for size comparison





Thanks for the reply. What values did you use for sun and sky ? default size and intensity for both? sun in realistic mode? Framebuffer rule of -5,24 exposure from PG skies calibration probably doesn´t apply here or am I wrong?

2018-07-25, 21:52:49
Reply #238

dubcat

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Thanks for the reply. What values did you use for sun and sky ? default size and intensity for both? sun in realistic mode? Framebuffer rule of -5,24 exposure from PG skies calibration probably doesn´t apply here or am I wrong?

I left everything at default settings and just aligned the sun to the HDRi sun. This particular sun angle needed -5.285 EV for true albedo.
Corona Sky is a dynamic map that changes once you add a Corona Sun, and then it changes based on sun angle. I used Light Mix to isolate Corona Sky from the Sun.
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2018-07-25, 22:41:54
Reply #239

johnymrazko

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Thanks , one more question - how do you isolate sun from hdri? Output node creates a mask and then Corona mix map with black color where the sun is and sky map for the rest?

Or painting in photoshop?

2018-07-25, 23:40:45
Reply #240

dubcat

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Thanks , one more question - how do you isolate sun from hdri? Output node creates a mask and then Corona mix map with black color where the sun is and sky map for the rest?

Or painting in photoshop?

Photoshop does not have 32bit floating point support, so if you open a HDRi in Photoshop and resave, it is basically ruined.

If you only have Photoshop, you can create a white mask where the sun is, and load it in 3dsMax as gamma 1.0
There are different methods you can split and add them together again, here is one example.



Affinity Photo has 32bit floating point support. So you can remove or isolate the sun inside the program.
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2018-07-26, 08:16:24
Reply #241

johnymrazko

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Are you using native 3ds max maps for a reason? would this work with Corona Mix and Corona Bitmap in the same way? when creating mask in photoshop, can I just add a new layer on the hdri and create mask? then is it correct to convert to 8bit and save as jpg? and then load into max with 1.0 gamma? In your last screenshot you showed that it is possible to avoid Corona Sun completely and use only masked sun to create direct light right? that 9999 rgb x 37 rgb is based on Corona Sun + Sky setup? matching 117 RGB value?

Also when using that hdri in real world scenario can I adjust exposure in framebuffer to my liking?

And how do you decide how large should the sun circle be? Do you include flares or only the sun disk?

Sorry for a lot of questions but I am trying to understand this to make it work correctly
« Last Edit: 2018-07-26, 10:07:51 by johnymrazko »

2018-07-26, 19:28:39
Reply #242

dubcat

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Hey!

Quote from: johnymrazko
Are you using native 3ds max maps for a reason? would this work with Corona Mix and Corona Bitmap in the same way?
You could use CoronaMix and disable "Perform mixing in sRGB space".
I usually drag and drop bitmaps into slate, and then run Corona Converter to convert them to Corona Bitmap.

Quote from: johnymrazko
when creating mask in photoshop, can I just add a new layer on the hdri and create mask? then is it correct to convert to 8bit and save as jpg? and then load into max with 1.0 gamma?
Yes to everything.

Quote from: johnymrazko
In your last screenshot you showed that it is possible to avoid Corona Sun completely and use only masked sun to create direct light right? that 9999 rgb x 37 rgb is based on Corona Sun + Sky setup? matching 117 RGB value?
Yes. I calibrated the HDRi sun to match isolated Corona Sun. Both will produce the exact same result.

Quote from: johnymrazko
Also when using that hdri in real world scenario can I adjust exposure in framebuffer to my liking?
True albedo matching is only necessary when we want to calibrate light and materials to real world values. When it's calibrated, you can use whatever you want to set  the mood.
If online stores could spend 1min extra when shooting HDRis, and just take a few pictures of a Color Checker or a 18% grey sphere. We could calibrate our HDRis to the actual capture.

Quote from: johnymrazko
And how do you decide how large should the sun circle be? Do you include flares or only the sun disk?
In this case I looked up at the NoEmotion sun. Moved a Corona Sun until it was in the middle of the NoEmotion sun, because the NoEmotion sun was huge.
Then I placed a standard camera at 0,0,0 facing south (south is the standard HDRi direction, the sun will show up in the center). Threw on a CoronaCameraMod, and enabled Projection type "Spherical". Then I changed the render resolution to match the HDRi and made a HDRi of Corona Sun. This is my mask.

When it comes to sun size, I guess it depends on what look you are going for. Sun size will not increase the light intensity of the sun, it will only make the shadows softer.
Most HDRi captures have a sun size of 2.
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2018-07-27, 22:00:42
Reply #243

Jpjapers

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Honestly, how do you know all this stuff?
Its fascinating to follow this thread. What is your background?

2018-07-27, 23:23:13
Reply #244

sprayer

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Photoshop does not have 32bit floating point support, so if you open a HDRi in Photoshop and resave, it is basically ruined.
from adobe page
Quote
In Photoshop, the luminance values of an HDR image are stored using a floating-point numeric representation that’s 32 bits long (32‑bits-per-channel). The luminance values in an HDR image are directly related to the amount of light in a scene.

2018-07-28, 00:54:33
Reply #245

dubcat

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What is your background?
Half Life 1 modder turned Archviz / BIM :)
My first introduction to 3dsMax was Autodesk Gmax, because Milkshape 3D was lacking a lot of features.

from adobe page
Quote
In Photoshop, the luminance values of an HDR image are stored using a floating-point numeric representation that’s 32 bits long (32‑bits-per-channel). The luminance values in an HDR image are directly related to the amount of light in a scene.

I've posted examples all over the forums for years, but I guess it's best I recap everything here.

I'm running the latest version.



#1
If you go back a few pages and download my ACES tonemapper script for Photoshop. You will notice that bright lights becomes black pixels. This is because Photoshop does not calculate negative values.
The script will split your render into two images and then divide those images together. Photoshop does not handle negative math well, and will return black pixels.

#2

Corona Sun



Corona Sun rendered as HDRi and re-saved in Photoshop as EXR.
Goodbye values.



Corona Sun rendered as HDRi and re-saved in Photoshop as HDR.
Better than EXR, still not what we expect.



#3

32bit floating point displacement.

Proper 32bit map rendered in Corona



Re-saved in Photoshop as EXR.
Since this map does not exceed 20 Photoshop Intensity, it will not clip.
Negative values work as intended also.



Re-saved in Photoshop as HDR.
Since this map does not exceed 20 Photoshop Intensity, it will not clip.
But since it's HDR, it will not have negative values.
It also has some weird ass shadow artifacts.



So if you use Photoshop you are left with these choices:

EXR: Clamped bright values and clamped negative values.
HDR: Somewhat proper bright values and no negative values.
Internal: Can't do negative math.

I bugged Adobe back in 2016 about this problem. They said they didn't understand what I meant about clipped values above +20 RGB, and asked me to take a print screen of the problem. (I had provided renders like the ones I posted here, but they wanted a print screen of the HDR image) That is when I gave up.
« Last Edit: 2018-07-28, 13:00:04 by dubcat »
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2018-07-28, 08:42:18
Reply #246

sprayer

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I've made some test,
Indeed Photoshop save EXR and HDR in half point, but value is the same. Not sure about negative value, i've test corona sun.
About 20-Photoshop clipping it's just own maths inside Photoshop, but value is fine if you see in other software. For example if you look at corona VFB sun value it's has own value, if you copy VFB to 3ds max VFB it's will have another, so i've check max VFB for re-saved images from photoshop we can load them via 3ds max image viewer. Also i was check in Affinity Photo it's showing the same value as in max VFB and can save EXR in float point by the way.
Also i have check re-saved PSD in Affinity, PSD store also the same value as in max VFB, so the problem goes from Photoshop export module, but PS can work with float point and store all colors but only in PSD file format.  I find at adobe forums what people advice to use some plugins for saving full EXR, i was used EXR loader from arionFX by the way. Native PS EXR loader can't load layers from 3ds max EXR and it seams can't save too

2018-08-02, 01:08:43
Reply #247

dubcat

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I dumped the iPhone 10.6 Telephoto Camera just for luls.
It has pretty soft darks and crunchy brights, not bad at all.
"Filmic Highlights" 1 should give you a nice start compared to ACES.

It's still RGB dump, haven't had time to fix my HSL/HSV dumper.
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2018-08-02, 11:07:28
Reply #248

Dionysios.TS

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here is a test with the 5ds dump, this is the correct way to use them? may be the higlights are too strong

I did a quick comparison against default ACES.
You have to use "Highlight Compress" 2.5 and "Filmic Highlights" 1 to match default ACES.
So leave "Filmic Highlights" at 1 and adjust "Highlight Compress" from 2.5 to taste.

edit:

I forgot to say that these settings only count for the Canon 5DS dump.

Thanks for your wonderful efforts here!
For the 5DS dump, "Filmic Highlights" at 1, and what about "Filmic Shadows"? I set t at 1 as well but my images are so contrasted, I needed to low down the contrast at 0.65 at least.

Thanks!

Dionysios -
Responsable d'Imagerie
Renzo Piano Building Workshop / Paris

https://dionysios.myportfolio.com/

2018-08-02, 14:28:35
Reply #249

Basshunter

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hi @dubcat

couple of questions here:

1) Do your LUTs (Like Canon 5DS .cube file) work in other render engines like V-Ray and FStorm or just Corona?

2) Would you kindly help me understand what ACES is? No matter how hard I try, I can't make sense of it!

Thanks!

2018-08-02, 21:15:45
Reply #250

dubcat

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what about "Filmic Shadows"?

Hey!

We use "Filmic Highlights" 1 because it only affects the highlight.
It does not mess with contrast. Here is a little 0-1 RGB dump, the curve continues like that above 1 float.
I can post some log dump examples of different tone mappers when I get time.



"Filmic Shadows" on the other hand, will only add some wonky contrast to your render.
The camera dump LUTs already contain contrast from the camera. So I would not recommend that you use "Filmic Shadows" in combination with the camera LUTs.



1) Do your LUTs (Like Canon 5DS .cube file) work in other render engines like V-Ray and FStorm or just Corona?
Hey!

They work in any engine that applies LUTs as sRGB. Corona and VFB+ are the only programs I know that extrapolate values above 1 float.
If you look at the sun and apply a normal LUT in Corona, the sun values are still correct. If you apply the same LUT in Vray, fStorm or Photoshop, the sun value will become 1 float or 255 RGB.


2) Would you kindly help me understand what ACES is? No matter how hard I try, I can't make sense of it!

ACES stands for "Academy Color Encoding System". ACES help unify different encoded material through a prosses called IDT.

But in this thread I'm only talking about the post production tools.
You can see and play around with the tonemapper here

https://www.desmos.com/calculator/h8rbdpawxj

4  Slope        - Controls the overall curvature strength.
7  Toe           - Controls the bottom half of the curve.
11 Shoulder   - Controls the top half of the curve.
8  Black Clip   - Moves the left anchor point below 0.
12 White Clip  - Moves the right anchor point above 1.

and of course the color space:



fStorm is the only engine I know that has ACES color space.
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2018-08-02, 21:40:35
Reply #251

Basshunter

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fStorm is the only engine I know that has ACES color space.

Is ACES a color space?

2018-08-02, 21:51:37
Reply #252

dubcat

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Is ACES a color space?

When your media has gone through the IDT process, it will be converted to ACES color space.
ACES color space is greater than the gamut of the human eye, so it's future proof.
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2018-08-02, 22:10:56
Reply #253

Dionysios.TS

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Thanks for getting back and clarifying everything! :)
Responsable d'Imagerie
Renzo Piano Building Workshop / Paris

https://dionysios.myportfolio.com/

2018-08-03, 04:10:25
Reply #254

aldola

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hi Dionysios.TS try the 5ds dump with 2.5 highlight compression, its works great

2018-08-03, 10:26:45
Reply #255

Dionysios.TS

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hi Dionysios.TS try the 5ds dump with 2.5 highlight compression, its works great

Thanks! This is what I did but I had some questions and doubts about the contrast.

Thanks again!

Dionysios -
Responsable d'Imagerie
Renzo Piano Building Workshop / Paris

https://dionysios.myportfolio.com/

2018-08-03, 17:18:56
Reply #256

oddvisionary

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Would you kindly help me understand what ACES is? No matter how hard I try, I can't make sense of it!

I have a lot of documentation from entry to med-high level if you want. here's some links :


https://www.slideshare.net/hpduiker/acescg-a-common-color-encoding-for-visual-effects-applications

https://acescentral.com/t/what-are-the-advantages-of-using-aces-for-color-correction/49
Freelance Post-Prod / Lighting & Look Dev 3D Generalist | VFX Designer | Sound Effect Recordist & Sound Designer

Corona Discord server : https://discord.gg/2uxq8EA

2018-08-07, 20:52:14
Reply #257

Basshunter

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I have a lot of documentation from entry to med-high level if you want. here's some links :


I'll check them out. Thanks for your time.

2018-08-08, 00:20:21
Reply #258

dubcat

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Every now and then I get questions about Reflection Level and IOR. I will use this post as a reference.

I associate Reflection Level with Opacity in Photoshop.
Imagine IOR inside a folder in Photoshop. This folder is Reflection Level. Bellow this folder you have a black layer.
The IOR/Black layer will always be 100% opacity. But you can change the Opacity of the Reflection Level folder.



When Reflection Level is 1, the folder inside Photoshop is 100% Opacity. We get 100% correct IOR values.



When Reflection Level is 0, the folder inside Photoshop is 0%. We only see the black layer. 0% IOR values.



If we change Reflection Level to 0.5, the folder inside Photoshop is 50%. We get 50% IOR and 50% black.



So what is 50% IOR.
First we need to convert the IOR value to Reflectivity.
Let's say our material is IOR 1.5.

Reflectivity = (((1-IOR)/(1+IOR))^2)*100 = 4%

Then we take 4% and multiply it by 0.5 (50%) = 2%

Let's convert it back to IOR.
IOR = 1/((2/(sqrt((Reflectivity/100))+1))-1) = 1.33

So if we use IOR 1.5 and 0.5 Reflection Level, our F0 point will be IOR 1.33 instead of 1.5.
But this is not the problem. The problem is that we also reduce the Fresnel edge by 50%. This edge should be pure white (1 float aka 255 RGB).
50% of 1 is 0.5, the Fresnel edge will be 127.5 RGB instead of 255 RGB. This is where our material is no longer physically plausible.

But since we have done the math, you can just change the IOR to 1.33 and increase Reflection Level to 1. This will give you the same result as IOR 1.5 and 0.5 Reflection Level. Only the material will be physically plausible.

When you buy models online, they usually come with ridiculous values like IOR 1.8 and Reflection Level 0.5.
These are not physically plausible, since Reflection Level is bellow 1.
Let's do some math and see what the actual IOR value is.
IOR 1.8 is 8.16 Reflectivity.
50% of 8.16% is 4.08%.
4.08% is IOR 1.51.
In this case they could just have used IOR 1.5 and Reflection Level 1, and the material would look the same and be physically plausible.

We can't touch Reflection Level, but there are two methods you can use to add imperfections to your reflections. (If we ignore bump/normal/displacement).
You have to ask yourself these two questions:
* Are these imperfections surface imperfections ? In that case you want to use a glossiness map.
* Are these imperfections caused by micro occlusion, small scale shadowing. In that case you want to use a custom IOR map to fake depth.
  Corona could auto generate this IOR map from a normal map, but that is currently not the case. (I will share a Normal to IOR LUT soon, but you have to do a few steps before applying the LUT).

If you have a cross specular scan of your material, it does not hurt to use my roughness to IOR LUT. Real world scans always include micro occlusion that Corona can not generate with glossiness or normal maps.

In Vray Next they have added this tool tip. Maybe Corona should do this too.



Here are some examples that show how F0 and the Fresnel edge gets clamped when you reduce Reflection Level.
The right square image is an unwrapped version of the sphere, where each vertical line is a degree. And the right image is a render in Corona.













TLDR;
* Leave Reflection Level at 1 for physically plausible materials.
* Use glossiness for surface imperfections.
* Use IOR maps for micro occlusion, small scale shadowing.
« Last Edit: 2018-08-08, 02:12:03 by dubcat »
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2018-08-10, 16:36:56
Reply #259

aldola

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hi dubcat, do you have more dumps to test? i enjoyed the last ones a lot

2018-08-11, 12:15:13
Reply #260

dubcat

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do you have more dumps to test?

Hey!

Do you mean camera luts ?
What cameras would you be interested in ?

edit:
If anyone of you have a camera request, let me know and I'll see what I can do :)
« Last Edit: 2018-08-12, 00:23:27 by dubcat »
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2018-08-12, 09:56:21
Reply #261

siebe

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The Canon 5D Mark I (classic) always had something special in the color rendition.

2018-08-14, 05:50:04
Reply #262

Basshunter

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Hey Dubcat.

Can I ask your opinion on something?

What do you think would be the best approach for recreating (Modeling and texturing) a highly detailed photorealistic reclaimed wood table top like this one?

I have no access to the real thing so scanning isn't possible.