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difference in Disney plausible shader

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difference in Disney plausible shader

Unread postby calincasian » Wed Mar 13, 2019 3:19 am

Hey there,

I'm seeing a difference between Clarisse and Houdini when using the Disney Plausible and an environment light with an hdr map.
I'm noticing the difference mostly in the reflections. In Clarisse it seems that the sun reflection size don't quite match. I got closer by adding 3% roughness in Clarisse but couldn't get rid of the harsh white reflections. Also The Clarisse image have slightly blurred reflections.
I have same number of reflected rays, 10 in both packages. Is there anything I'm missing?

cheers
calin
Attachments
testHoudini.jpg
testClarisse.jpg
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Re: difference in Disney plausible shader

Unread postby mdkai » Wed Mar 13, 2019 9:30 am

Hi

To be fair mantra and clarisse are quite different render concepts , and the Disney principle shader is a paper all devs have to read and implement.
Now I'm sure each does things a bit different , some features in the shader are added or not described in the paper ..So it's not unusual to have slight variations..

Looking at it from my phone I spot not many heavy differences at all to be honest.

Cheers
Kai
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Re: difference in Disney plausible shader

Unread postby dboude » Wed Mar 13, 2019 9:42 am

Hi,

Perhaps it comes from the sampling resolution of your env light. Try to increase it. Or you are using mipmapping for your hdr texture...

Env_Sampling_Rez.png
Env_Sampling_Rez.png (11.52 KiB) Viewed 316 times


Edit : I don't now Mantra but perhaps it clamps the value by default. You can try to do the same in Clarisse at the renderer level. Set the Sample Clamping to 1.

Cheers ;)
Démian
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Re: difference in Disney plausible shader

Unread postby calincasian » Wed Mar 13, 2019 10:46 pm

Kai, I was expecting some slight variations however in this case in my opinion there is a lot of differences and that's why I posted and ask the community about parameter changes to get it closer.
Maybe the filtering on the jpg image soften some of the issues and I'm more concerned about the harsh highlights where there's no roll off.
Demian might be right and it could be a light issue, I've changed the sampling resolution and still the same, I've also clamp the samples to 1 at the render node. Here is a cropped version and hopefully it will show the pure white highlights.

cheers
calin
Attachments
testHoudini.jpg
testHoudini.jpg (42.75 KiB) Viewed 266 times
testClarisse.jpg
testClarisse.jpg (43.2 KiB) Viewed 266 times
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Re: difference in Disney plausible shader

Unread postby mdkai » Wed Mar 13, 2019 11:02 pm

You can pick sample that area. Looks like its the sun in your HDRI, and indeed it seems like it is clipped in Mantra.
This give more pleaseant looking highlights but it also means these are clamped values.

Clarisse does not clamp any highlights by default, which is why the white pixel appears. They happen if values between pixels are extrem far off.
I.e.:when the sun is proper exposed, pixel values for lights can jump from 0.75 to 15000 .. Since you can not really make a smooth transition, it shows as hard pixels.
Simply change the clamping, like Démian suggested from 10 to 2 or even 1 !
clampingSample.jpg
clampingSample.jpg (20.95 KiB) Viewed 259 times


Cheers
Kai
Last edited by mdkai on Wed Mar 13, 2019 11:26 pm, edited 1 time in total.
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Re: difference in Disney plausible shader

Unread postby calincasian » Wed Mar 13, 2019 11:17 pm

yes, sorry forgot to mention in my last post that reducing the sample clamping to 1 helped a lot. there are still some odd pixels here and there but overall I think I'm fine with the result. Thanks everyone for helping out.

cheers
calin
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Re: difference in Disney plausible shader

Unread postby dboude » Thu Mar 14, 2019 9:32 am

You're welcome ;)
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