On Thu, 03 Mar 2005 17:45:15 +0100, Roland Scheidegger <[EMAIL PROTECTED]> wrote: > Brian Paul wrote: > > Roland Scheidegger wrote: > > > >> here's a patch which mainly does 3 things: - convert sis, mach64, > >> and radeon to spantmp2. The sis and mach64 drivers got a slight > >> change, previously you could not read back alpha values (always > >> 0xff) and I don't think there was a good reason for that? > > > > > > IIRC, the mach64 doesn't support destination alpha planes. OpenGL > > requires that reads of absent alpha planes returns 1.0. I don't know > > if the SiS chip is the same. > Are you sure? At least the driver handles things like GL_DST_ALPHA blend > factors, wouldn't you get awfully bogus results if it wouldn't support > destination alpha planes in that case? It does not export BGRA visuals > however for some reason. Note that r128 driver (which was converted to > use spantmp2 by Ian and thus got that same change in behaviour reading > back RGBA pixels already) does not export visuals with a alpha component > neither (just BGR 888, if I read that right). SIS OTOH exports BGRA visuals. >
I think the mach64 had some limitations regarding alpha. I think it could only do fog or alpha, but not both at the same time. perhaps what you are seeing is a result of that. Alex ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
