Can't clean up reflections

[GregCooper]

I've created a sample scene to replicate an issue I'm having in a much larger scene. I can't seem to get clean/correct looking reflections on a glass material (vraymtl) when compared to CPU even at low quality settings. The reflection of the lampshade is passable but the refl/spec of the bottle shows up with really hot single pixels instead of a nice blur as with the CPU image. I do have DOF turned on as it will be in the production scene. Can't figure out if this is something to do with the DOF calculation or the reflection. Even if I crank the min/max subdivs and lower the noise threshold right down with CUDA it never seems to get the bottle reflection right.

I've tried tweaking quite a few of the render and material settings but it always seems to render the same. Is there something I'm missing in regards to rendering reflections on CUDA?

Using Vray Next for Maya Update 2. Images and test scene attached.

[Karol.Osinski]

I think GPU engine needs higher sampling than CPU. In Sample Rate render element you can clearly see that GPU pass is much noisier / red / green. That makes me think GPU engine reaches its max subdivs faster therefore it is harder for it to reach the noise treshhold. O would try going up to 100 max AA subdivs and then maybe increase the shading rate and see what happens.

[^Lele^]

Shading rate isn't taken into account with GPU: assume it to be 1, and change the sampling accordingly (i.e. raise max AA, ideally by a lot.).
Noise threshold ought to be the stop criterion, not max AA.

[Karol.Osinski]

Shading rate isn't taken into account with GPU

- Thanks for clarifying it Lele, it crossed my mind at some point that GPU's sample rate pass simply does not work correctly.

[GregCooper]

Okay thanks Lele. I thought I was going high with 64 max subdivs but it makes sense to just control it with the noise threshold. I'll give it a go.

[Micha]

You could render a shading rate pass and check it. I found that 1/100 are good subdiv values for daily use in GPU mode.