On Wed, Mar 13, 2002 at 02:02:25AM +0100, Dieter N�tzel wrote:
> On Tue, Mar 12, 2002 at 23:41:23, Ian Romanick wrote:
> > S3 owns S3TC, not FXT1 and not the VQ in the RagePro and not the VQ
> > in the PowerVR SG.
>
> We have to convert from S3TC to FXT1 (UT for example).
Alle klar! Yes, if you decompress S3TC textures in your driver you are
using S3's IP. Fine. However, the ARB_texture_compression spec makes
absolutely NO REQUIREMENT that you do this. As far as I know (and perhaps
Brian can comment more), it is 100% for an application to do:
glTexImage2D( GL_TEXTURE_2D, 0, GL_COMPRESS_RGB_ARB, width, height,
0, GL_RGB, GL_UNSIGNED_BYTE, image_data );
and have the driver select the compression mode (if any) to use. The driver
is the free to use S3TC, FXT1, or anything else it chooses. If I read the
spec correctly, the driver can even choose to ignore the internal format and
just use GL_RGB.
In fact, I believe that this is *exactly* what Quake3 and RtCW (and probably
other games) do. TTimo, is that correct?
Given that, I see no reason (but I'm not a lawyer) why support for the
GL_3DFX_texture_compression_FXT1 extension or any other non-S3TC texture
compression could not be implemented in Mesa / DRI. Look at the extension
spec again.
There is NO mention of decompressing S3TC textures and recompressing them to
FXT1. 3dfx did that in their Windows drivers purely to better support the
installed software base the was already using the S3TC extensions. Since
there really is no such software base (besides UT) on Linux, we don't have
to worry about that. :)
http://oss.sgi.com/projects/ogl-sample/registry/3DFX/texture_compression_FXT1.txt
--
Tell that to the Marines!
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