On Tuesday 05 April 2005 16:11, Brian Paul wrote: > Roland Mainz wrote: > > Another item would be to look into what's required to support visuals > > beyond 24bit RGB (like 30bit TrueColor visuals) ... someone on IRC > > (AFAIK ajax (if I don't mix-up the nicks again :)) said that this may > > require an ABI change, too... > > I doubt an ABI change would be needed for that.
Are you sure about this? I thought we treated channels as bytes everywhere, unless GLchan was defined to something bigger, and even then only for OSMesa. Even if it's not an ABI change, I suspect that growing GLchan beyond 8 bits while still preserving performance is non-trivial. > > When I look at xc/extras/Mesa/src/mesa/main/config.h I see more items on > > my wishlist: Would it be possible to increase |MAX_WIDTH| and > > |MAX_HEIGHT| (and the matching texture limits of the software > > rasterizer) to 8192 to support larger displays (DMX, Xinerama and Xprint > > come in mind) ? > > If you increase MAX_WIDTH/HEIGHT too far, you'll start to see > interpolation errors in triangle rasterization (the software > routines). The full explanation is long, but basically there needs to > be enough fractional bits in the GLfixed datatype to accomodate > interpolation across the full viewport width/height. > > In fact, I'm not sure that we've already gone too far by setting > MAX_WIDTH/HEIGHT to 4096 while the GLfixed type only has 11 fractional > bits. I haven't heard any reports of bad triangles so far though. > But there probably aren't too many people generating 4Kx4K images. Yet. Big images are becoming a reality. DMX+glxproxy brings this real close to home. > Before increasing MAX_WIDTH/HEIGHT, someone should do an analysis of > the interpolation issues to see what side-effects might pop up. Definitely. > Finally, Mesa has a number of scratch arrays that get dimensioned to > [MAX_WIDTH]. Some of those arrays/structs are rather large already. I looked into allocating these dynamically, but there were one or two sticky points (mostly related to making scope act the same) so I dropped it. It could be done though. - ajax
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