How much memory does a scene use?

[arobbert]

All of this talk about GPU rendering has got me thinking. If a given scene must fit into the GPU memory you need to know how big the scene is. How do you tell?

[vlado]

Good question. Will see if we can print some statistics on that.

Best regards,
Vlado

[arobbert]

No one knows this? Are you just buying a GPU and hoping it will work?

[Alan Iglesias]

No one knows this? Are you just buying a GPU and hoping it will work?

Well, yeah, pretty much at this point. Since RT is initially mostly targeted for bringing down the waiting time for test renders previewing lighting, texturing, reflections and so-forth, folks should be able to pare down large scenes to fit in GPU RAM space for test renders while still leaving enough in the scene to get a real good idea of what it all is going to look like when you go for the production render.

That being said, it looks like we will be gettting some scene RAM use stats that will help even more with this.

-Alan

[vlado]

No one knows this? Are you just buying a GPU and hoping it will work?

Well, a very rough guide is that 1 million triangles require about 150 MB of VRAM, and each texture - 2 MB (assuming GPU texture size of 512 x 512). However older cards have a limit on the amount of VRAM that can be allocated in one chunk, even if there is more VRAM available. Fermi-based cards are a lot better in that regards.

Best regards,
Vlado

[arobbert]

Thanks Vlado!

[vlado]

So I did some actual tests with two scenes, one has 4,580,499 triangles and takes 440 MB of GPU memory (which gives about 97 MB per million triangles), and the other one has 4,730,314 triangles and takes 678 MB of GPU memory (which is about 144 MB per million triangles).

Best regards,
Vlado

[Bpositive]

What about the actual size of the textures, doesn't that matter then? And how about proxies?

It seems you can fit quite large scenes on the GPU!? Then why all the fuzz about about vram sizes! I'm confused...!

[Alan Iglesias]

What about the actual size of the textures, doesn't that matter then?

Since RT GPU takes each texture map and reduces them to a standard size (512x512 is the default, IIRC), then I'd imagine the bigger issue is the amount of textures rather than their actual size...

-Alan

[Bpositive]

Okay, I can see the spinner now. And the maximum is 2048.

I think you should at least have the option to make that larger. If you for instance have a scene with only a few but large textures.