Characters with Displacement

[pipe_mm]

Hello dear Chaosgroup people,

we are in the middle of production of a commercial and there is a weird bug around displacements.

I have 3 characters in the scene. All of them use a soft bercon noise as displacement.
It works perfectly for two characters, but it always stops at lightcache calculation when I activate the dipl for the third guy.

This is RTX GPU Rendering on a superfast machine running a RTX4080 (also tried it on another computer with RTX3080ti)
The problem does not occure in CPU mode (only GPU)

I have tried a lot of different displacement settings, and naming of the input connections, without any luck.
Perhaps you could take a look at the scene and hopefully help find the issue
https://pipe.green-cloud.at/index.php/s/xW5nFnSf9j3rZDc

thanks a lot
Martin

[Twist]

Looks like it's working fine here.

Rendered on a 3080ti, vray 6.00.03 hotfix 1, maya 2023.3

[pipe_mm]

thnx for testing - hmmm

[pipe_mm]

haha trallala
it seems to be related to the combination of displacement and the AL shader.
rendering the three guys with standard MTL or vray fast SSS is no prob.

but try to apply a AL shader (and turn the SSS mix on) and - badabing badabong - the scene crashes

very curious me

(the image shows the guys with standard SSS shader + diplacement)

[pipe_mm]

yep - this does the trick - going back to good old vrayFastSSS from ALsurface makes the scene render.
too bad, for I really like the AL material.

[pipe_mm]

actually this isnt a happy solution
the look on the character changes tremendousely, switching from AL to SSS

I am pretty sure there is a GPU instability in the combination of displacement and the AL shader
thnx for support

[oglu]

Have you tried the translucency ss in the standard vmat?
I like how easy it is to control.

https://docs.chaos.com/m/mobile.action#page/66690483

[pipe_mm]

thnx Oglu for your reply - yes I use it in combination with blurry refractions, but never as a pure SSS material. As a support for a blurry refraction it is very beautiful, but also very renderheavy. will run a little test on it. thnx

[oglu]

Yes its random walk ss. This should work great.

[Muhammed_Hamed]

+1 on using the translucency in V-Ray's material, it uses Random Walk SSS(multi scatter) and will get you much better results than FastSSS2 or Alsurface(both use a single scatter)
You need to set GI bounces in IPR to 16 or use LC in IPR for this to work well

RandomWalk is slower than other solutions for now, this is improved in the upcoming update to V-Ray GPU. Uniform mode will be supported on GPU, on average it is 2x faster than the older directional algorithm, plus it gives better results with low poly meshes.

About the instability with displacement I will test on my side, as always if you get me a scene, or if I can reproduce on my side I will make sure the issue is solved

Best,
Muhammed

[oglu]

I like the look!

[pipe_mm]

thnx for your active participation in here.
I tried the translucency SSS of the VrayMTL but its giving a to strong refraction on the eyelid, making the pupil shine through.
so I sticked to standard FastSSS for this production.

attached some render tests with translucency SSS scaling 0,1 0,2 1,0

[Muhammed_Hamed]

Thanks for sharing! I think this depends on geometry. For Random Walk it is best if the surface is water-tight
For SSS mode you need to disable refractivity, and use scale and SSS color to control the effect
For Volumetric mode, it could be used with refractivity

If there is a chance to share this little guy under NDA, I would love to test with. The issue with the eyelid I can make a request for improvement to our developers
my Email is muhammed.hamed@chaos.com

Best,
Muhammed