Needs to be updated on this page: http://cgit.freedesktop.org/mesa/mesa/tree/docs/GL3.txt under GL 3.0.
Phoronix: Mesa Can Do EXT_texture_compression_RGTC
In Mesa's quest to catch up to the proprietary Linux drivers (and the graphics drivers available under Windows), they are now a tiny bit closer. David Airlie has announced on the Mesa mailing list that he has implemented support for the EXT_texture_compression_RGTC extension into Mesa...
Hey, at least we recently moved up to 2.1 instead of 1.4...
I believe S3TC is DXT3, and these are DXT4 and 5.
Does anyone know what they're used by? Does this help WINE apps?
Correction: it can replace DirectX's 3Dc/BC5 (which is better than DXT5).
Totally wrong, RGTC is red+green block texture compression. S3TC is RGB and RGBA block compression. How is BC5 (which is a RG compression formats) supposed to replace DXT5 (which is a RGBA compression format) if BC5 can only handle two color channels?!
Your statement is still wrong though. An RG format can never replace an RGB/RGBA format. Using DXTn formats for normal compression was always kind of a hack.
Addition to last post:
The very nVidia article you quote explains why using DXTn for encoding normal/tangent data is a hack.
If anything, then texture_RG and texture_RGTC are the proper ways to store such information.