Author Topic: dubcats secret little hideout  (Read 110222 times)

2018-08-02, 01:08:43
Reply #240

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 #241

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 #242

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 #243

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 #244

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 #245

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 #246

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 #247

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 #248

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/

2018-08-07, 20:52:14
Reply #249

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 #250

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 #251

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 #252

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 #253

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 #254

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.