max 3D texture size on ATI X1800 512MB card

OpenGL OpenGL: Advanced Coding
1

Greetings,

What is the maximum 3D texture that can be loaded on ATI X1800 512MB card? The theoretical limit is reported as 2048x2048x2048. However I am unable to load more than 512x512x600 (8-bit, GL_LUMINANCE).

nVIDIA 7800 GTX although having 512MB, limits 3D textures to 512x512x512. Any idea if this will be increased in future drivers?

thanks,

Maniam

2

Hint: 2048x2048x2048 = 2^33 = 8 Gb
512x512x600 ~ 2^27 = 127 Mb
(assuming 1 byte per texel).

The first limit is just teoretical, it’s not possible with 512 Mb videomem.

3

I think that 2048^3 refers to the maximum
size in each dimension, so e.g. a 2048x32x32
3D texture should work.

4

I did some testing, and it turns out ATI has the same limitation; glTexImage3D() calls work on 3D texures (8-bit, GL_LUMINANCE) upto 512x512x512 only. 512x512x1024 returns GL_OUT_OF_MEMORY.

I tried using in-between non-power-2 sizes, but the driver hangs.

Fine, so I try loading 2 512^3 8-bit textures, which amounts to 256MB. I still get GL_OUT_OF_MEMORY ! I don’t know why I’ve paid more for video memory that doesn’t seem to be getting used!

This sucks… Hope this is just a driver bug?
Has anyone had similar experiences?

thanks,
Maniam