I'm trying to figure out how OpenGL compresses and mipmaps 3D textures. From the spec, I gather that mipmaps are just 2x2x2 down-sampled (cube filtered) versions of the original. But how might one compress 3D images for S3TC, by compressing each slice independently, or by taking slices together somehow? I have a working version of the 2D version, but I'm not sure how to proceed with 3D. I'm thinking slices but not sure.
I know that OpenGL can do this for me, but I want this addition to my library.
Any insight would be appreciated.