I want to use DXT5 compressed 3D textures. On nVidia this works very well using the NV_vtc extension. However, on ATI I did not find this extension to be supported.
So, does ATI support compressed 3D textures in any way? D3D seems not to support nVidia’s specific vtc format, but it supports to compress each 2D slice using DXTn, which of course gives the same compression ratio, it’s just a different format. I couldn’t try it with ATI in OpenGL so far, though.
The S3TC extension does not mention 3D textures, at all.