shading errors on opencl

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lacilaci
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shading errors on opencl

Post by lacilaci »

I've noticed this behavior when rendering using path+opencl
It was discussed in some threads somewhat before. Long triangles are rendering dark. However on cpu it's not a problem, why is that?

Also raising min epsilon helps a bit but in my example rough glass is somewhat darker anyways. And in other cases with some cad files backfaces render dark/not black using gpu but on cpu it's ok.
Which can be pretty annoying when everything looks ok and then I switch to cpu+gpu and suddenly all kinds of artifacts appear. Is this something that can be fixed?

Attached also a primitive example scene(just use any hdri with it)
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cpu.jpg
ocl.jpg
shadingerror.blend
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lacilaci
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Re: shading errors on opencl

Post by lacilaci »

rough glass, cpu+gpu vs gpu only. 20 sec. rendering
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cpu_and_gpu_20sec.jpg
gpu_only_20sec.jpg
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Sharlybg
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Re: shading errors on opencl

Post by Sharlybg »

put minimum epsilon value to 0.0001 instead of 0.00001 :
dgr.jpg
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lacilaci
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Re: shading errors on opencl

Post by lacilaci »

maybe for better illustration, cpu vs gpu roughglass.
cpu roughglass is also extremely slow to compute.
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cpu_roughglass.jpg
gpu_roughglass.jpg
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lacilaci
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Re: shading errors on opencl

Post by lacilaci »

Sharlybg wrote: Thu Sep 06, 2018 11:25 am put minimum epsilon value to 0.0001 instead of 0.00001 :

dgr.jpg
I've mentioned this in my first post..
This doesn't help always, and it makes problem less visible not gone completely in other cases(and problem is not visible on cpu only). Also, rough glass is rendering differently with gpu than on cpu.
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