Author Topic: dubcats secret little hideout  (Read 109418 times)

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

subpixelsk

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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 -
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Renzo Piano Building Workshop / Paris

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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