Author Topic: dubcats secret little hideout  (Read 101569 times)

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 -
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Renzo Piano Building Workshop / Paris

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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
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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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   (____|___|     https://www.twitch.tv/dubca7 / https://soundcloud.com/dubca7 / https://dubcatshideout.com  ( ͡° ͜ʖ ͡°)

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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   (____|___|     https://www.twitch.tv/dubca7 / https://soundcloud.com/dubca7 / https://dubcatshideout.com  ( ͡° ͜ʖ ͡°)

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.

2018-08-14, 16:07:43
Reply #263

aldola

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i love hisao suzuki work, but i dont know the camera he used, may be someone here knows it

2018-08-14, 16:32:07
Reply #264

oddvisionary

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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.

Zbrush. Seriously, with some wood brush, this is the most efficient way for sculpting/modeling your reference.
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2018-08-14, 20:19:59
Reply #265

Basshunter

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Zbrush. Seriously, with some wood brush, this is the most efficient way for sculpting/modeling your reference.

Thanks for your opinion Oddivisionary. I appreciate it.

Can I ask you something else?

once the sculpting is done, how would you approach texturing process?

2018-08-15, 00:41:38
Reply #266

oddvisionary

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Zbrush. Seriously, with some wood brush, this is the most efficient way for sculpting/modeling your reference.

Thanks for your opinion Oddivisionary. I appreciate it.

Can I ask you something else?

once the sculpting is done, how would you approach texturing process?

Pleasure. I'm not a Zbrush specialist but there is two ways :

- Sculpt a non detailed version of the wood, and add the textures using Mari/Substance Painter (including bump or normal or displacement) : this way you have a bit more freedom in the texturing processs. You can use photo scanned seamless textures as well as a starting point.
- Texture directly from Zbrush as I've seen some incredible texturing done with it.
Freelance Post-Prod / Lighting & Look Dev 3D Generalist | VFX Designer | Sound Effect Recordist & Sound Designer

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2018-08-21, 07:50:37
Reply #267

subpixelsk

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Hi dubcat, I got into hdri calibration thanks to your tips thank you! However I would like to somehow calibrate hdri that has partially overcast sun - is that possible in any way? or is it just eyeballing then? for example some of noemotion evening hdris so that the intensity of direct light would be correct

2018-08-21, 11:04:41
Reply #268

romullus

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And one more question about HDRI from me. I remember you mentioned that photoshop damges HDRI files uppon saving them. How would be possible to check if a file was crippled? I took two files, one with unclipped dynamic range in HDR format and another with clipped range in EXR format, made simple offset adjustment in photoshop and resaved both in their respective formats. Both files came out at almost exact same size (difference is within few bytes), both have unchanged dynamic range and renders identical to unmodified files (except for the shadow position, of course). For me it looks like the files weren't damaged at all and are perfectly safe to use. Am i missing something? I would like to adjust transformation of most of my HDRIs, but before doing that i want to be sure that i won't do any irreversible damage.
I'm not Corona Team member. Everything i say, is my personal opinion only.

2018-08-22, 13:48:27
Reply #269

Dippndots

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@romullus regarding EXR, if you save a "32-bit" EXR from photoshop and try to use it in max, the window that pops up after selecting the file will list each channel as 16-bit, if you have ProEXR, I'm under the impression that it saves correctly?