Elladan wrote: > On Fri, Jul 05, 2002 at 08:15:26AM +0100, Keith Whitwell wrote: > >>Elladan wrote: >> >>>Yes. I'm seeing the same thing on my Radeon 7500. See screenshots >>>here: >>> >>>http://www.eskimo.com/~elladan/tux >>> >>>(Or in the bug report I filed on the dri project page...) >>> >>>I'm also seeing generally horrible problems with tuxracer whenever it >>>uses multiple textures on the same polygon, as far as I can tell. >>> >>>There seemed to be a few other bugs in the database on multitexture >>>problems, too... >> >>It's to do with multipass rendering, I think, rather than the texture code >>specifically. >> >>The same problem gives you the 'shimmery' ice patches. The mesa gloss demo >>shows similar artifacts.
> Where would this problem most likely reside in the code? Any guesses? > Eg., file/function areas? I can go playing around in there if someone > have some vague idea what the problem might be... > > -J This sounds like Z-buffer fighting. If you draw the same triangle twice with exactly the same vertices you'd expect that the same Z values would be generated for each fragment. But the OpenGL spec doesn't require that to be true, depending on particular state changes between passes. (See the OpenGL spec appendices). If the first triangle is drawn in hardware but the second is drawn with software (or vice versa) you almost never get exactly the same rasterization results. I've also seen cards which will do both passes in hardware but still produce different Z values. glPolygonOffset() is the usual solution to this problem and its up to the application programmer to know when to use it. Strictly speaking, the gloss demo should use glPolygonOffset() for the second rendering pass. But it doesn't because I was lazy when I wrote the demo. So, if my hypothesis is correct, this is an application problem. -Brian ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek We have stuff for geeks like you. http://thinkgeek.com/sf _______________________________________________ Dri-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/dri-devel
