CUDA/OPTIX Killer Shader

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Sharlybg
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CUDA/OPTIX Killer Shader

Post by Sharlybg »

Related to this topic here : viewtopic.php?f=4&p=29932#p29932

And This error :
Sharlybg wrote: Mon Apr 26, 2021 12:04 pm Strangelly since quite sometime i'm not able to render big project on Nvidia CUDA/ OPTIX. ONly OPENCL is working on the 2060super i'm working with. I was trying to compare OPTIX vs No Optix on huge assets scene. It constantly crash before starting. And this on official Blendluxcore 2.5 and blender 2.83.
Sometime textures disappear randomlly on some object during final render even if visible in viewport and material preview. Sadly as theses are most of the time big Project i can't send it to DADe to look into it as he need small size repeatable error file for investigation :|
Here : viewtopic.php?f=5&t=3511&start=20

I found that a mesh with both procedural shader and textured glossy Transluscent material is the source of the problem. I manage to have it on simple cube scene.

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Dade
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Re: CUDA/OPTIX Killer Shader

Post by Dade »

I'm going to check this tomorrow.
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Re: CUDA/OPTIX Killer Shader

Post by Dade »

This is something we have already seen in the past: you are mixing a transmitting material (glossytranslucent) with transparency (or opacity, I never remember how it is called in Blender).
This is, in general, a bad idea because it does mess the volumes stack (sometime you hit the surface, sometime you don't because of transparency).

The best work around should be to use "glossy" instead of "glossytranslucent" and to edit the alpha mask image to have "0.75" instead of "1" (so it is 25% transparent).

It is a bug but it is an ill condition very hard to track on GPUs.
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Re: CUDA/OPTIX Killer Shader

Post by Sharlybg »

But this the best way to make realistic foliage and leaves with 3d renderer. It is 1n extremelly used combo in archviz.
Grass trees pampas flowers all use this. It even the method followed in Cycles and Maxwell felixrender.

Simple glossy will not give you this realistic glowing scattering effect. And you can't avoid opacity features as you need that to define leaves shapes with less geometry.

In addition it work on buggy opencl on nvidia and not on Optix with the same nvidia gpu.
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Re: CUDA/OPTIX Killer Shader

Post by Sharlybg »

Look like the bug is still there on 2.6 build. People could easily get this brutal crash condering the amount of Nvidia user and LOL plant package.
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