[Mesa-dev] Mesa Perspective Texture mapping

[Jeff Slutter]

Hi,     I'm currently porting Descent 3 to Linux using Mesa as the OpenGL renderer.  Using the same source code as the Windows version except for the initialization and any other glx specific things I have gotten it all ported.  However, there seems to be some issues with the perspective texture mapping.  I'm not quite sure if this is on our side, Mesa or maybe even glx (I'm using the NVidia glx X-Server for my TNT and the one for Matrox for my g400), but remember that this is the same source code as the Window's version.  I've also talked to John Carmack at Id on how they do their texture mapping coordinates for Quake (since Mesa and Quake get along quite well).  Where we are different is that Carmack uses OpenGL for transformation and clipping, while we don't.  I have found a hack of sort which improves the texture mapping for D3, however, it still isn't fixed.     It would be a great help to me if I could get in contact with someone to maybe help work out these problems.  At the end of this email I have included the source code to how we calculate our texture coordinates.   Thank you for your time, Jeff Slutter Outrage Entertainment   our texture map coordinate setup code: (done for each vertex, pnt)     float texw=1.0/(pnt->p3_z+Z_bias);   texp->s=pnt->p3_u*texw;   texp->t=pnt->p3_v*texw;   texp->r=0;   texp->q=texw;   My hack was to remove the *texw for the s and t coordinates...that fixed 95% of the problem, however, any polygon clipped on the screen suffered perspective issues.