How does the GPU memory and scene size relate?

[particlerealities]

I'm putting together a parts list for a new workstation and am trying to figure out how many GB of memory my new graphics card will have to be.

Attached is a screen grab of a recent model I just created. For V-Ray RT GPU, I'm assuming I'd need a video card with about 6GB of memory to handle this particular scene? Can anyone confirm if that's the case? Am I looking at the correct indicator of file size?

Please note I paid ZERO attention to file size as I built the model. I could have optimized texture maps/sizes, geometry, etc., and will in the future. Since I can't currently use GPU rendering, I haven't even worried about it till now.

[Alan Iglesias]

I don't have a formula for you, but I can tell you that RT/GPU seems to use significantly less RAM than the Physical RAM number you get in the Summary window after a typical rendering. For instance, a recent rendering that used just about 3GB in the summary window rendered on the GPU using 675MB, which was reported by the EVGA Precision GPU monitoring/overclocking tool.

I'm guessing that the summary number is really all the RAM that is being used at the time which of course includes the application with the loaded file. The GPU apparently is only going to be concerned with the the actual scene rendering data, which seems to be much less.

Exactly how much less, I cannot sure until more testing, but I would still buy the most RAM possible for my GPUs if I am going to be trying to render entire scenes in GPU on a regular basis.

Hope this helps some,

-Alan

[particlerealities]

Thanks Alan - I noticed when I looked at the DOS window for V-Ray RT, there was a line item for "Memory usage: X.XX MB". I wonder if that's the number that matters? If so, the previously mentioned model indicated 168.63 MB, but then it loads the Bitmap files, and now it's crashing (just updated to the newest V-Rary version this morning). Joy.

[Alan Iglesias]

Thanks Alan - I noticed when I looked at the DOS window for V-Ray RT, there was a line item for "Memory usage: X.XX MB". I wonder if that's the number that matters?

I did a test rendering here and the Memory Usage line you speak of was relatively low, at 25.9MB while the GPU was reporting a 641MB RAM usage. I'm no expert, but it seems that on the console the line was reporting RAM used before maps were loaded, so perhaps that has something to do with it.

I'm sure Vlado can be much more specific about all this, but these are my findings at this point...

-Alan

[vlado]

The line in the console output refers to geometry only; as Alan pointed out, it does not include any textures for the time being. We can add more diagnostics for GPU memory usage if you think it will be helpful.

Best regards,
Vlado

[Alan Iglesias]

...We can add more diagnostics for GPU memory usage if you think it will be helpful.

Well, as long as the GPU monitoring app is correct in terms of RAM being used, I think we're in pretty good shape there (I'd rather have you spending your time adding RT/GPU features!).

So would it be safe to say that the GPU will be using less RAM than Max typically reports because just the rendering info is going to the GPU, and not the RAM used for application and loaded file data?

Thanks Vlado,

-Alan

[particlerealities]

Thanks Vlado - I personally think knowing exactly how big the scene is when it is transferred to the GPU would be very beneficial to knowing how much "space" you have left to play with, but I'm not aware what "GPU monitoring app" Alan is referring to - is there already something out there that does this? Maybe since I can't currently render to GPU is the reason I've never seen it.

(Just got approved today to buy a GTX 580 for testing speed improvements before I start buying tons of them and putting them in my current farm computers)

[Alan Iglesias]

Just got approved today to buy a GTX 580 for testing speed improvements before I start buying tons of them and putting them in my current farm computers

Grab the EVGA 580 Classified if you can. It's the fastest and arguably best made 580 out there and can be overclocked under warranty. Run the EVGA Precision tool whenever you are rendering and monitor the temps and memory usage.

Most importantly, Have Fun!

-Alan

[particlerealities]

Thanks - that's actually the one I'm looking at! If I can prove a big enough speed increase to my bosses, I might be able to a bunch more of them. Or at least a pair for my workstation, then the rest with EVGA GeForce GTX570 HD 2560MB cards.

[Alan Iglesias]

I'm currently running two 3GB GTX 580 boards in my workstation and and although I realize that things will improve greatly over the next few years, right now 1024 cores are doing a wonderful job for me in RT/GPU.

Just make sure you have the power and cooling to support the boards and you should be all set...

-Alan

[Guest]

I am attempting to hit the nail on the head with GPU rendering and memory usage so I ran some small tests. I started by going to the 3ds Max summary info which states the GPU bench mark scene vlado supplied is 7GB physical and almost 10GB virtual memory. I am not sure if this differs during render time?



When I hit render using the default settings, the V-Ray log states the scene is 40.94mb and I understand this is without any textures? The textures themselves add up to only 1.68mb.



Then I used MSI Afterburner to monitor my GPU memory during rendering. Here is a screen shot before I clicked render so I knew how much memory had been taken up already by other applications and system tasks and a screen shot during the rendering.



GPU 1 shows an increase of 228mb and GPU 2 shows an increase of 258mb. There also seems to be differences between using production and active shade as I ran these tests too. Production rendering seemed to take up more GPU memory.

[3LP]

In my opinion, it would be great to have a helper in the scene, or a button somewhere where it can calculate the ram used for the render.
We could monitor the memory before actually send a render and have Vray.exe crashing. It's annoying specially when I have DR assigned and I forgot to unchecked it.
I need to check all the nodes again after to make sure all the RT are working properly. RT is not hot jumping nodes in the scene like the normal DR so when one RT is crashing or not responding, I need to stop everything and restart everything again.
This is specially annoying with the fact that when we are spawning, the geometry is uploaded from the master computer and not the server who has mostly just a 1Gb ethernet cable and not teaming of 10Gb cables like the server, so it can take a while to send the render out on the nodes to see at the end that it's crashing.

If a monitor tool allowed us to tweak all this before rendering, this would be great, and save a lot of time!

Any news about new features for DR with RT in general, cpu and gpu?

Thanks

Stan