Texture ram

[ACFred]

Texture RAM is memory on a video card that is devoted to manipulating your textures, thereby decreasing the load on your CPU, RAM and standard video chip.
For instance, my card has 92MB on it, 32MB is devoted to textures. It seems to help a little bit, but my card is a little older (Wildcat II 5000).

[moin]

hey, thanks. cleared up some things!!!:)

[anthonymcgrath]

hey ACFred, can you show me where to find out how much texture ram is used by my machine? I'm on windows xp. If you could also show tell me how to adjust it for maya that would be cool. cheers.

[ACFred]

It's actually graphics card specific and, typically, only highend graphics cards have memory devoted to only texture swapping. What graphics card to you have? I'm not sure how the newer multimedia cards such as GeForce4 and ATI cards deal with memory, but we can definitely figure it out.

[MDC]

For the lowend cards, GeForce, Radeon, etc, the memory on the card is used for texture storage, and if needed, textures are stored in main memory and swapped very quickly across the AGP bus. I'm not sure exactly what the advantage is to having seperate onboard texture memory on a video card such as the Wildcat other than to minimize the possibility of texture swapping with main memory. Typically, the memory in your video card will look like this.

Total 64 Megabytes:

At 1280 x 1024 x 32 bpp color

Approximately 5 megabytes will be what's called a front buffer. The front buffer is the image that is currently being displayed.

Another 5 megabytes is dedicated to the back buffer, the back buffer is the image the graphics cards is drawing to display next.

And finally you'll have usually and 8 bpp depth buffer (z-buffer). This is used to create depth in a 3D scene. At 1280x1024 it's just over a meg.

So for this simple setup you're using about 11 of your 64 megs for just display. If you are using a 16 bit depth buffer, or triple buffering, or doing anti aliasing you use up even more memory.

Sticking with the original simple example, we have roughly 52.5 megs left for textures. The thing is though usually the textures will be mip mapped. This means the same texture will be duplicated and scaled and filtered decreasingly smaller each time so as the texture get's further from a camera it doesn't shimmer. So if you have a 512x512x32bpp texture with 5 levels of mip maps, in memory it's stored at these resolutions 512x512, 256x256, 128x128, 64x64, 32x32. This one texture alone can take up a couple megs of memory uncompressed if it's mip mapped.

I don't know of any software that actively monitors your video memory usage, other than tools game programmers have written for them selves. Your computer using OPen GL or Direct X will manage this all by itself, so you don't need to worry about it much. If you are building scenes that use large ammounts of textures and you want to display them real time, just get a card with a lot of video RAM and you should be fine.

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