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Brian Hanke avatar image
Brian Hanke asked

Arnold GPU is slow and noisy

What's the deal with Arnold GPU? Cycles GPU in Blender is 2-4 times faster on the same scene. GPU-only renderers are extremely fast. But I can't get any speed improvements with Arnold GPU. Almost without exception scenes render slower and end up noisier when using GPU mode. Am I missing something? I've messed around with adaptive sampling but it doesn't seem to make much difference. I'm using a laptop with a 6-core i7 and a 1070. I've attached two renders: 3m23s CPU, 4m10s GPU. CPU looks beautiful but the GPU one is FAR noisier. CPU was at 8/2/2/2 and GPU was 20AA (no adaptive sampling).3m23s.png

4m10s.png

gpu
3m23s.png (1.1 MiB)
4m10s.png (1.3 MiB)
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Thiago Ize avatar image
Thiago Ize answered

Shaders with refraction and reflection are known to be noisier on the GPU than on the CPU and so will require more samples to converge. Are you finding that GPU is slower in scenes that aren't all just glass-like like in your shader ball example? If you change the shader ball to not be transmissive how does it compare?

Finally, what version of mtoa/arnold are you using? Try to update to the latest (arnold core is at 6.1.0.1 as of today).


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Brian Hanke avatar image
Brian Hanke answered

> If you change the shader ball to not be transmissive how does it compare?

Wow, big difference there. Changing the material to be only diffuse and spec really let the GPU shine. 6:55 for CPU, 2:02 for similar noise level on GPU, 3:13 and it's substantially cleaner than CPU. Very nice! Much more what I expected from a GPU renderer (50-75% faster).

I have the most recent MtoA and Arnold versions. Are there any plans to improve Arnold GPU performance on glass/SSS materials?

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If you mean the converging of noise, then yes.
This is an ongoing process, and it's not a quick fix.
If you see render engines that handles these things faster, it is very likely they are more mature, or they fake/cheat, do things that eventually will sacrifice quality in one way or the other.

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Brandy Kennedy avatar image
Brandy Kennedy answered

@Brian Hanke when you did away with the transmission, what did your glass look like? I am absolutely fighting Maya GPU rendering tooth and nail to get a clean glass render. At best it's about half the quality of CPU, and taking 3 times as long. I have decent specs for a laptop. I feel like it should support a faster render for either CPU or GPU, but I'm just not getting them.

11th Gen Intel Core i9-11900H @ 2.50GHz , RAM 32.0 GB, NVIDA RTX 3050 Ti

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Honestly I don't even try to use GPU any more. I feel like it's designed with Quadro/RTX cards in mind, so it doesn't offer any advantage on prosumer-level hardware. I stay on CPU and I'm very satisfied. One thing you can check regarding noise reduction is the sampling on your lights. Even going from 1 to 2 samples can make a big difference.
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