Difference in render output ADV vs GPU

[sheehan_partners_nm]

I am completely new with Vray GPU, so did a quick test out of curiosity. Same scene, just switch the Production mode from vray Adv. to Vray RT ( Cuda+CPU). Didnt mess with the settings at all.
GPU is giving me a way more accurate material look. In the first picture you can see how well bump and reflections are treated in GPU. The second one is much more flat.... Why is that?

[savage309]

V-Ray GPU and V-Ray Adv are two different render engines. Renders between them are not guaranteed to match (in fact, they will almost never will). They use completely different algorithms and approaches. Most likely this difference is caused by the bump map.

If you want render to match between CPU and GPU, you can use "V-Ray GPU CUDA running on CPU", or as we call it - hybrid rendering. Check about it here (keep in mind that hybrid rendering has the GPU feature set).

Best,
Blago.

[sheehan_partners_nm]

Hey Blago, thanks for answering. Yes, I was aware they are completely different engines, that's why I have been using the traditional ADV all the time for production works.
As you suggested, I used hybrid for the test, faster rendering with both resources. I am surprised how much "better" Vray GPU looks! Seems like there is no bump map at all for the ADV test, which is rendering perfectly during the other test.

[vladimir.nedev]

The most likely reason for the difference in those renders is that the GPU renderer doesn't perform filtering on the textures.
That's very important to get all of the detail out of the bump/normal map.
You can disable the filtering for the production renderer as well, just for your bump/normal map and see if that helps.

Greetings,
Vladimir Nedev