Vray GPU rendering slightly more noisy/messy despite better settings then CPU

[zach_ryder]

I built this scene out in GPU, but when I switched to CPU, the cpu results looked better as far as noise goes. I had the cpu max sample. at only 20 and the gpu was at 100. I even had the light cache at 3000 for gpu, despite cpu being only 800. Still, when you some in, there is still a lot of noise from the gpu rendering. I'll attach a closeup as well. Does anyone know why this is? Is it because cpu is that much better at understanding light? because this scene does have more then just natural light.

[vladimir_krastev]

Hi, thanks for posting. You can not compare the V-Ray GPU and V-Ray CPU settings directly. The hardware is completely different and the settings for the sampler differ a lot. Please take a look at this thread and especially this post.

[zach_ryder]

I know they produce different results I just didn’t know GPU always produces more noise. Is that true? I’ve tested multiple scenes now with very high GPU settings

[zach_ryder]

I have the max subdiv setting in Vray set to 200. When I I’ve tried 300 but there seems to be no difference

[vladimir_krastev]

I just didn’t know GPU always produces more noise. Is that true?

This is not true.

There could be something in the scene that is causing issues. Try something like 2000 - 3000 and if there is no difference in noise we could review it. Please send it over using the support contact form and include a link to this thread in you e-mail so we can track you issue faster.

[zach_ryder]

I've set it to 200 MAX Subdivs withen the vray UI. So the actual number would be much more (can't remember the actual equation), but your saying to set the Max Subdiv slider to 2000-3000? when I set it to 500 it sometimes doesn't render. I have a rtx 3080

[vladimir_krastev]

HI, try to increase the samples limit from here:


Leave the light cache as it is. If increasing the samples limit and eventually decreasing the noise threshold does not make any difference then there could be something in the scene that is causing issues.

[zach_ryder]

So iv'e tried that as well. Honestly I've tried everything for about 3 hours. My conclusion is that gpu just produces a little bit of noise when you zoom in far to an object. Especially if the scene has more light sources than 1. I've tried multiple past projects, all of which were built for gpu. Iv'e tried really amping up the light cache, and it definitly helped, but when I render the scene in cpu, with max subdivs at 20, the results are better. The only reason I care is because I was just about to build a nice gpu set up. Is there any way i can send someone my scene maybe?

[Morbid Angel]

I built this scene out in GPU, but when I switched to CPU, the cpu results looked better as far as noise goes. I had the cpu max sample. at only 20 and the gpu was at 100. I even had the light cache at 3000 for gpu, despite cpu being only 800. Still, when you some in, there is still a lot of noise from the gpu rendering. I'll attach a closeup as well. Does anyone know why this is? Is it because cpu is that much better at understanding light? because this scene does have more then just natural light.

Just curious what the render time difference was, was it worth the gpu route? The render looks nice by the way. Just needs to be tonemapped.

[zach_ryder]

GPU was much faster (almost half) and that's compared to chaos cloud CPU. I't just slightly bothers me that I can't figure out how to get less noise on the gpu. Had plenty of samples and the noise limit was slightly smaller then cpu. Also, the light cache was much higher.

I guess on the plus side none of my clients notice. It's only really visible when you zoom in, but it is definitely there

[vladimir_krastev]

Hi, by looking at your example images again the CPU one looks a lot more blurry. Are you using Denoiser in both examples? Are you rendering with Brute Force and Light Cache for the CPU? The image filter can also have an impact especially as we are looking at it with a lot of zoom in. But it could as well be something in the scene. Are you using a IES for the spot lights in the ceiling?

[zach_ryder]

Yes I used IES lighting. Does that have something to do with it? I used denoiser on both

[vladimir_krastev]

Hi, have you tried to tweak the GPU Utilisation settings? We can try to help reduce the noise in the GPU render but we will need to review the scene. Please send it over using the support contact form and include a link to this thread in you e-mail so we can track you issue faster.

[zach_ryder]

Is there a GPU Utilisation rollout for sketchup?

[vladimir_krastev]

Hi, thanks for posting. I am not an expert in Sketchup but I see that you have opened a ticket. Our colleagues will answer you as soon as possible. Please send us your scene for review with all assets used in it using the ticket.