On 17 Jul 2002, Michel Dänzer wrote:

> On Tue, 2002-07-16 at 20:17, Leif Delgass wrote: 
> > On Tue, 16 Jul 2002, Keith Whitwell wrote:
> > 
> > > > Well, it's not high on my list.  I don't think flat-shading is used that
> > > > often, and the changes don't have any effect on smooth shading.  Actually, 
> > > > it _eliminates_ some saves/restores necessary for unfilled polygons with 
> > > > hardware flat-shading.
> > > >  
> > > > Actually, I think the problem is larger than mach64.  Rage128 has the same
> > > > problem and it appears to have GL compliant flat-shading based on the
> > > > primitive.  The problem is that for clipped polygons, the primitive type
> > > > changes, so flat-shading breaks down in that case (like with unfilled
> > > > polygons).  I think the templates would have to be changed to copy the
> > > > provoking-vertex color of the polygon being clipped into the vertices of
> > > > the triangles generated by clipping, rather than interpolating the color.
> > > 
> > > I'm surprised that this isn't working.  Can you verify?  I tested on the i810 
> > > at the time & definitely got clipping working there...
> > 
> > Here's a couple screenshots with the r128 driver (20020629 build):
> > 
> > http://www.retinalburn.net/linux/r128-unclipped-flat.png
> > http://www.retinalburn.net/linux/r128-clipped-flat.png
> > 
> > Allen's test program is attached.  Maybe someone could check this on 
> > Radeon with software tcl as well?
> 
> Broken, as expected. As we've both been reporting for some time,
> software clipping is broken in the r128 and radeon drivers. I used to
> suspect a Mesa problem, but the mga driver works. I wish I knew what to
> look for about this problem...

Actually, since mga uses DO_FLAT in the templates, the provoking-vertex
color gets copied to all vertices.  I think the problem is with
interpolation and drivers that define DO_FLAT as zero.  Keith said that
i810 worked, but it _doesn't_ set DO_FLAT, which is the define that
controls whether colors are copied.  It sets HAVE_HW_FLATSHADE, but that
just causes colors to be saved and restored when working with unfilled
tris.

-- 
Leif Delgass 
http://www.retinalburn.net



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