Testing RT GPU noise

Common Common :: Hardware
1

I’m testing RT GPU 3.10.03 to see if we can use it as a production renderer. I currently have a GTX 970. The time needed to resolve noise to an acceptable level takes about the same amount of time as the the standard production renderer using the adaptive sampler so there doesn’t appear to be an advantage. The noise is mostly visible in glossy refractions and reflections but also in the shadows.

It appears the only way to reduce the noise is to throw more processing time at the whole scene. Raising the subdivision settings of the lights and materials does not seem to have any affect. Am I missing something in the settings?

What kind of speed improvement would I see by adding an additional GTX 970? Would it reduce render time by 50%? How much faster would a Titan X or Z be?

2

It depends on what CPU you are comparing to?

Best regards,
Vlado

3

I’m assuming you are already using the light cache for secondary GI? This only works when V-Ray RT GPU is a production renderer.

Other than that, the GPU renderer doesn’t have any quality settings. Your only option is to get more and/or faster GPUs.

V-Ray 3.2 will improve the noise levels, and also the GPU render speed generally, so you might want to wait a bit until then.

Best regards,
Vlado

4
5

Thanks for your reply. When will this build be out? Do you have any idea of what kind of speed increase there will be adding an additional card?

6

Well, one can easily add multiple GPU to a motherboard for “cheap”.
If you’d want to do the same with the cpus, you need to go for xeons, and they are quite expensive.
I have 3 GTX 970 here and it can outperform a dual xeon 2970 v2. but for way way way less $.

Stan

7

V-Ray scales almost linearly, meaning that adding 2 cards make the rendering ( almost ) two time faster ( keep in mind that the GPU memory does not stack. 2 cards, 4 gigs each makes 4 gigs, not 8 ). I think that a modern CPU can feed at least 8 GPUs without any trouble.
If everything is okay, probably the build will be released next week.

8

thanks for your replies

9

unless i am mistaken (very possible, i dont use rt gpu much) it defaults to a noise threshold of 0.. if i understand right, this means it will continue refining all the pixels until the time limit is reached.

setting a higher noise theshold (i.e. 0.004) means when easily resolved areas reach that threshold, the gpu will stop refining them and focus its efforts on the areas that still need it.

in my head at least this means a big speedup, as the gpu will be working on progressively less of the image as time goes on.

am i talking out of my a** or is this correct? if so a default of 0 for threshold isnt a good setting at all for speed.

10

Thanks for the tip. This does seem to be the case.

11

ahh glad to see it wasnt just me. in this case id suggest Chaos change the default noise threshold to something that uses the gpu more efficiently. i cant see why you would ever want noise threshold of 0.