GPU (RTX) rendering big quality problems vs. CPU rendering

[andykerstens]

Hi all,

I’m using Vray Next for Sketchup a few years now. I did always render on CPU only.
I just bought a new desktop pc with following specifications:

AMD 3990x
MSI Nvidia RTX2080 Ti (11GB) (driver studio version 442.19)
128GB Ram
Windows 10 Pro
Sketchup 2020
Latest Vray Next version

Before this new pc I had a desktop (Intel Xeon E5 1650 v4 + Geforce GTX 1080), using Sketchup 2018 + Vray next.
I did always render on CPU only, because the production render result with Cuda, or GPU only were very noisy and wasn’t the same quality output as the CPU.
I thought, with my new setup, this would be better, but it isn’t. The result, and quality differences are simular as with the old hardware setup.

Now I do have the latest ‘Studio’ driver version, but I did also try it with the older driver version.
In attachment the screenshots of the setting, and actual production render. Please also note the difference in glass an carpet textures in the render. (cpu vs. gpu)
Please download them via following link to have all settings and renders: https://www.dropbox.com/sh/db5uergsa...7hdVHG2pa?dl=0

I always used the default setting from Vray itself (high, and one time very high for the gpu only).
I also downloaded 2 models from Chaosgroup to do the same test between cpu and gpu. This is also in attachment. (interior / exterior model)
https://www.chaosgroup.com/vray/sket...utorial-videos

I looked up things, but really can’t find any solution, or the base problem.
Could someone help me out?

Thanks!

[DCHA34]

Hi,
check this parameter:
GPU Textures / Resize = Full-size textures and not Resize textures

[andykerstens]

Hi,
check this parameter:
GPU Textures / Resize = Full-size textures and not Resize textures

Thanks for the feedback!
Unfortunately the noise is not gone. The overall quality is still very bad compared tot the CPU rendering.
he texture of the carpet worked well after setting the textures not to resize.

[Micha]

Hi andykerstens

I suppose so you run in the biggest V-Ray pitfall I know - the default render setting presets of VfSU/R. This settings are implement from someone who try to destroy V-Ray. ... it's a joke, but true is this setups cause that you don't get the results you would expect. If I would use a V-Ray for Rhino/SU trial and use this settings, I wouldn't buy V-Ray.

I tried to bring it on the table, for example here:
https://forums.chaosgroup.com/forum/...lc-sample-size


Attached two screenshot for progressive and non progressive GPU rendering. Try this and let me know what you get. Never use the default presets!!! They cause noise and longer render times. Hands off from this and you will be happy. Only you need to touch for faster previews or finer noise is the noise threshold. For large rendering increase the LC subdivs.

For example the presets set a larger LC sample size for faster rendering but this caused a 4 times slower render time at one of my interior scenes. So, be careful. An other example - texture shouldn't be downsized, the on-demand mipmapping is a great feature to get full quality, no need to downscale.

I use two 2080ti for my daily GPU renderings since more than a half year and I'm very happy about speed and quality. The V-Ray plugin for SU and Rhino is a great tool with a lot very nice functions. But the tiny presets destroy anything.

[andykerstens]

Hi andykerstens

I suppose so you run in the biggest V-Ray pitfall I know - the default render setting presets of VfSU/R. This settings are implement from someone who try to destroy V-Ray. ... it's a joke, but true is this setups cause that you don't get the results you would expect. If I would use a V-Ray for Rhino/SU trial and use this settings, I wouldn't buy V-Ray.

I tried to bring it on the table, for example here:
https://forums.chaosgroup.com/forum/...lc-sample-size


Attached two screenshot for progressive and non progressive GPU rendering. Try this and let me know what you get. Never use the default presets!!! They cause noise and longer render times. Hands off from this and you will be happy. Only you need to touch for faster previews or finer noise is the noise threshold. For large rendering increase the LC subdivs.

For example the presets set a larger LC sample size for faster rendering but this caused a 4 times slower render time at one of my interior scenes. So, be careful. An other example - texture shouldn't be downsized, the on-demand mipmapping is a great feature to get full quality, no need to downscale.

I use two 2080ti for my daily GPU renderings since more than a half year and I'm very happy about speed and quality. The V-Ray plugin for SU and Rhino is a great tool with a lot very nice functions. But the tiny presets destroy anything.

Hi Micha,

Thanks for your reaction. All the detailed settings behind the default settings are just 'Chinese' for me. Your settings work really well actually!
The only thing is this render took 20mins and the startup time is also quite long. While the render on CPU did about 10mins, and is still some better quality.
Cuda, combining both GPU and CPU is not really better for the render times, and is also not the same quality as the CPU.
I thoughtt GPU rendering would be much faster, but if you want quality is takes at least the same time, it looks to me.

Once more, many thanks!

[Micha]

Your CPU is very powerful, so the single GPU has a problem. It looks like a 3990x is approx. so fast like two 2080ti. GPU renderings is interesting on the long run if you work with multiple GPU and if you need to upgrade from time to time. It's easy to add four new GPU, but it's a lot of work to upgrade the CPU.

Right, the startup time of the GPU is to long. Hope it can be optimized by the team.

[konstantin_chaos]

Hi guys,

Here are some facts which should clarify things a little:
1. The Quality presets were created back in the day for CPU rendering (emphasis on bucket rendering). And for mid range systems they do work very well.
2. The Very High preset is intentionally limited to avoid excessive render times.
3. The quality preset settings are shared between the CPU and the GPU (in bucket mode). Unfortunately the sampling is quite a bit different between the engines which leads to higher noise levels on GPU.

So here's what we'll do to improve the experience:
1. The preset settings will be updated giving you better image quality for slightly longer render times
2. A new preset can be added using even higher settings. This will work great for people that are mainly concerned with quality and not that much with render times
3. We'll try separating the GPU and CPU presets to ensure somewhat consistent noise levels

* The changes listed here will not be part of Update 2. The'll come at a later stage after extensive testing.

To improve the quality of the GPU result in the current version one can just increase the 'Max Subdivs' to 40, 60 or even 100 (in rare cases).

I suppose so you run in the biggest V-Ray pitfall I know - the default render setting presets of VfSU/R. This settings are implement from someone who try to destroy V-Ray. ... it's a joke

Micha, this is rude and untrue as I explained above...

They cause noise and longer render times

The settings you suggested will render longer for sure.

For example the presets set a larger LC sample size for faster rendering but this caused a 4 times slower render time at one of my interior scenes.

This is true to some extent.
We'll have to update the light cache settings a bit to account for slowdowns caused by the re-tracing.

Konstantin

[Micha]

Hi konstantin_chaos ,

please forgive me my provocative words. I tried to talk about a serious problem, that the wrong preset setups will cause that Chaosgroup lost potential users and frustrate exist users, if they get noisy results only. The situation doesn't changed over months. The presets can't be used to get speed&quality and your trial users got lost. Is this an acceptable situation, if an easy solution is possible? The engine is fantastic, but the wrong setup can cause that the goal is never reached.

I wrote my thoughts about the weak result not without to test it before. For example the high and very high presets. Turn on the sampling rate output and you will see the disaster. An interior will show you a nearly complete red sampling rate output, since much higher max subdivs are needed to reach the wanted noise threshold. Like you wrote 40..100 are needed and not 18 or 24 only. And I observed it with my interiors and 100 is often needed to get enough samples against the noise.

But instead to enable more samples for "Very high" quality, only the min subdivs are increased - which cause longer render times, but not a finer noise. The user is waiting a long time and finally he don't get "very high" quality, only low preview quality again. The extreme tight limit of 0.003 can't be reached if only 24 subdivs are available.

And the LC problem - I rendered large 360° panoramas and my deadline was tight. I tried "medium" but the render time was very long. I was very surprised that I got 400% speed increase by editing the sample size only. I used a finer sample size and got much more speed. It's a big difference if your output needs 2h or 30min. If you need to render 4 panos and other renderings too, than this little wrong option can cause a lot of trouble.

I hope you forgive me and understand my motivation to bring the focus on this serious issue.

[konstantin_chaos]

Hi Micha,

I understand that this has to be addressed.
But i was hoping for a change in the way the GPU engine does it's sampling.

In any case I'm currently running numerous tests in an automated way and based on the results we'll update the settings.

The minimum subdivisions increase is intentional and very necessary in some situations:
It removes completely black buckets in dark areas of the image.

The LC issue is a real thing and will be resolved.

I hope you forgive me and understand my motivation to bring the focus on this serious issue.

It's cool.
I highly appreciate the feedback you're giving us.

Konstantin

[joey145]

Hi, here is the short, simple solution to your problem:

1. Select RTX or CUDA (Vray Next for Sketchup Update 2)
2. Set 'Quality' to 'High'
3. Render Parameters > Quality > Max Subdivs: 42 (default is 18 )
4. Forget about CPU rendering

If you want less noise, just raise the Max Subdivs. At around 60 you won't even need Denoiser.

Have fun!

[Micha]

joey145 And if you set at the light cache raytrace 1 and sample size 0.01 you could get more speed, most for interiors. The best way to find the right max subdiv is to enable the sampling rate output channel. If you get to much noisy red areas, the max subdivs needs to be increased. For me below 50 caused to much noisy at critical areas like blurry metals.

[konstantin_chaos]

Hi guys,

I've just uploaded a new stable nightly build.
https://nightlies.chaosgroup.com/mai...table/20200416

Here's the announcement thread where you can see the most important changes listed:
https://forums.chaosgroup.com/forum/...lable-20200416

In it the quality presets have been updated in a big way.
There are 6 quality levels now which should give you consistent results when switching engines or samplers.
In order to achieve that we had to do a lot of testing and introduce some significant changes.
You'll notice that now the min and max subdivision values are visible independent of the render mode or engine.
The Max Subdivs in particular change automatically when you go from CPU to GPU and vise versa.
This was key when pursuing consistent quality.

Please give this build a try and let me know what you think.

Regards,
Konstantin

[fprpic]

Sorry to bump just like this, but I've been struggling with those presets for quite a white, and I was thinking to open a topic about it...
I will try a new nightly build. Thanks