making cpu scene render with gpu rendering

[digitarch]

Muhammed,
as your gpu shaderball testscene renders fine but our scenes don´t we need some assistance in converting our existing scenes and workflows to gpu rendering. We we now save your shaderball rendersettings and try them with our scenes..
Matthias

[digitarch]

Muhammed, opened our scene and used your shaderball testcene rendersetting. Still doesn´t render. Logfile attached. Then we rendered with material override - maybe it´s any map or shader problem.

[digitarch]

ok, now our scene with your rendersettings and material override. less errors but still no rendering

[digitarch]

Muhammad? What to do now?

[Muhammed_Hamed]

Sorry, I just saw your post. I will move this thread to the correct forum now
Swap GI to BF and use Cuda mode in performance tab. Let me know if this helps

Could you please share more information on your scene setup? Does it use proxies, displacement, FP?

Best,
Muhammed

[digitarch]

Muhammed, sorry, didnt see the vray gpu forum (quite at way scrolling down the screen

[digitarch]

I found the vray gpu list: https://docs.chaos.com/m/mobile.action#page/60100952

does that mean that if we use any of the incompatible features the scene wont render? (Using vraymap for showing blueprints in viewport but they are of course hidden while rendering)

[Muhammed_Hamed]

Hi digitarch

V-Ray GPU is a separate renderer, optimized for speed and built from scratch to utilize the GPU hardware. There are known limitations in the link you shared, it is best to start your new scene using the GPU engine from the start. This way you avoid any differences or limitations on swapping

It is also possible to render your current scenes with V-Ray GPU, with some tweaks. Did you swap to Cuda and try with your scene?
Some of the errors you got above are because of exceeding the GPU memory. Is it possible to upload me one of your scenes? I will tell you what is causing the errors and how to approach this

Best,
Muhammed

[digitarch]

Muhammed, Swap GI to BF and use Cuda mode in performance tab didn´t help. We start now with a new project from blank screen for testing gpu performance and see ....

[Muhammed_Hamed]

Good luck!

Please let me know if you have questions on the GPU workflow

Best,
Muhammed

[digitarch]

Hello Muhammed,

thank you for your help, i really apprechiate it.

I now tried to compare GPU and CPU rendering in my current project by using VRayMaterial Override with a grey Material to keep things simple.

I did a lot of test rendering with different Noise Thresholds comparing the rendertimes.

Here are some results:

V-Ray GPU 5 Bucket Mode, CUDA, Brute Force, Samples limit 3000, Noise limit 0,2, RTX only
1min16sec
V-Ray GPU 5 Bucket Mode, CUDA, Brute Force, Samples limit 3000, Noise limit 0,2, hybrid
1min6sec
V-Ray 5 Bucket Mode, Brute Force, Max Subdivs 100, Noise threshold 0,2
43 sec

V-Ray GPU 5 Bucket Mode, CUDA, Brute Force, Samples limit 3000, Noise limit 0,05, RTX only
5min00sec
V-Ray GPU 5 Bucket Mode, CUDA, Brute Force, Samples limit 3000, Noise limit 0,05, hybrid
3min55sec
V-Ray 5 Bucket Mode, Brute Force, Max Subdivs 100, Noise threshold 0,05
3min16sec

V-Ray GPU 5 Progressive, CUDA, Brute Force, Samples limit 3000, Noise limit 0,2, RTX only
57sec
V-Ray GPU 5 Progressive, CUDA, Brute Force, Samples limit 3000, Noise limit 0,2, hybrid
1min11sec
V-Ray 5 Progressive, Brute Force, Max Subdivs 100, Noise threshold 0,2
57sec

V-Ray GPU 5 Progressive, CUDA, Brute Force, Samples limit 3000, Noise limit 0,1, RTX only
2min5sec
V-Ray GPU 5 Progressive, CUDA, Brute Force, Samples limit 3000, Noise limit 0,1, hybrid
1min35sec
V-Ray 5 Progressive, Brute Force, Max Subdivs 100, Noise threshold 0,1
1min38sec


As you can see in Bucket Mode CPU rendered much faster than GPU in both cases did (RTX as well as hybrid)
Using Progressive GPU Hybrid rendered a bit faster than CPU, but RTX alone still remained very slow.

Now our question is whether we didn't set up GPU rendering correctly?

I attached a Link of the scene and both cpu and gpu rendersettings for you to download:

https://we.tl/t-N0IKOWKG47


Thank you in advance.

Best regards, Marco

[Muhammed_Hamed]

Thank you for the scene, digitarch

Here are a few tips to help with your testing,

-Your test runs need to be at least 5 minutes for accurate results, V-Ray GPU takes a few second to move geometry and texture to system memory then GPU memory. So if your render time is 1 minute, half of that is probably the process of moving the scene into VRAM.
-Use 3000 LC Subdivs for interior scenes, this affects both V-Ray and V-Ray GPU, specially the GPU engine, this can double your rendering speed.
-Use the sky texture in a domelight not 3Ds Max environment slot, the Domelight is always faster (Applies to both V-Ray and V-Ray GPU)
-Disable displacement from Global Swatches, unless you manually match the look between the 2 different engines. Right now displacement looks so different between the 2 engines.
-Delete render elements for such tests to be safe
-Use RTX mode, it is super fast for the type of scene. The hardware acceleration is very helpful
-Your goal should be achieving the same noise results, the GPU engine gives cleaner results and slightly brighter by default. You need to keep that in mind, you need to adjust your noise threshold to make for a fair comparison. Check below

I used slightly higher resolution in my testing, to make sure the testing is accurate

Clay test,
V-Ray Bucket mode, 5950X CPU 16 cores/32 threads >> 49 Minutes 31 Seconds
V-Ray GPU Progressive mode, RTX 3090 >> 3 Minutes 17 Seconds

For this test I used .01 noise threshold for V-Ray and .02 noise threshold for V-Ray GPU, and still the result of V-Ray GPU is cleaner

Beauty test,
V-Ray Bucket mode, 5950X CPU 16 cores/32 threads >> 58 Minutes 43 Seconds
V-Ray GPU Progressive mode, RTX 3090 >> 10 Minutes 4 Seconds

.01 noise threshold for V-Ray and .02 noise threshold for V-Ray GPU

So why am I comparing V-Ray's Bucket mode to V-Ray GPU progressive mode?
This is the recommended way of using each renderer, V-Ray(CPU) is fastest and most efficient with bucket mode and V-Ray GPU is fastest with progressive mode









Have a great weekend!

Best,
Muhammed

[digitarch]

Hello Muhammed,

Thank you so much for the detailed response!

We will try your settings and see if we can reproduce it.


Best regards, Marco

[Muhammed_Hamed]

Good morning digitarch

Let me know how this goes, your 3060 should be exactly half of the 3090's performance. You can match your results with mine above, it should be close

Best,
Muhammed

[Witt3D]

Hi, found this thread really important for us,as our study is thinking to move on GPU rendering too.
Not that much info about GPU rendering, on this forum and even on the internet, at least not very delighting one.

We really have several FAQS about this issue, and we didnt achieve to find out simple answers, although we think they have to be somewhere.

First of all, sorry Muhammed, but we find out not a fair comparision the one you are just showing up.

· RTX 3090 cost around 2.500 euro, but 5950X just 500 euro. A better comparision should be RTX 3090 with Amd Ryzen 3970X.
· We can accept the point of view with the noise thresold, but both has to been render with the same method, progressive method consumes more memory and has some limitations, so it is also an unfair comparision.

This is more or less what we have find out on the internet. Not fair comparisions, and not clear info about some important points that we gonna point out here, so perhaps Muhammed and chaosgroup can put some light on it..

The first point would be to compare with the same method (progressive or bucket) and with two equal price piece of hardware, GPU and CPU. This can give us a good starting point to know, where ever we have to spend more money pon GPU or CPU to get speed improve. We havent find nothing close to this on the internet. And it all about money. Where we should put all our budget in.
Second point, is assuming GPU will be faster than CPU (we dont really know cause we cannot get a decent test with equal hardware and equal method), we get to an important limitation about VRAM memory on GPU.

Right now, a normal scene on our study consumes about 100 - 140 GB RAM. Lots of polygons, high resolution textures, displacement and high resolution final image.
No graphic card has this amount of VRAM, we know it seems that GPU needs less VRAM than CPU does, but do we have a good criteria to know if we can render our scenes with GPU?, or do we have to spend thousands of euros on a workstation with the latest Graphic cards, and after that hit render and get memory exception error?
Some of our questions are regarding this matter. And it would be greatful that someone in Chaosgroup put some info on this.

We have read a lot about this matter, and we have come close to confirm that some Nvidia cards with NVlink can share their VRAM memory. It seems, but havent get an official reply, that Vray 5 is ready to handle it. Is it so?
How much Vram do we need, when we need 120 GB for CPU? More or less, nothing like, it depends on bla,bla,bla,... . Just a rough value. So we come close to know how many graphic cards do we have to link with Nvlink.
Next, if VRam is not enough, Vray is compiled to work with the Ram memory of the computer, even if it slows a bit the render, or you just cannot render the image? Cause i really know that if i have n AMD Ryzen 3990X with 256 GB RAM i can render whatever i want, pretty sure aobut this. It can take a night long, but i can render it on high resolution image. Is it the same with GPU? Or we get a point where we have spend 8.000 euro on a workstation and we hit render and get an error and no final render?

This are some of our questions that need to get an answer before we decide to move on GPU Rendering if finally we do so.

Thank you.