[Bug 20626] r200 texgen with glVertex4f(x, y, z, w) error

[<bug...@fr...>]

http://bugs.freedesktop.org/show_bug.cgi?id=20626





--- Comment #13 from Roland Scheidegger <sr...@tu...>  2009-03-17 18:32:26 PST ---
(In reply to comment #12)
> > Yes, I do the same operation under ATI's windows driver, and no problem with
> > disabling texgen R or Q, (and when enable all of texgen STRQ, they looks like
> > not set R200_TEXGEN_FORCE_W_TO_ONE), so I guess they maybe have another way to
> > set q to 1.0 when disable texgen Q. To play with R200_TEXGEN_FORCE_W_TO_ONE is
> > not a right way but a useful way sometimes.
> > And sometimes when we disable some of the texgen coords, the r200 produce
> > unexperted results, this maybe we have no right way to generate q coord(for
> > examples, q is zero), but ATI can do it!
> 
> An acceptable way maybe when user disable texgen Q, driver can enable it on
> R200, and set q1 = q2 = q3 = 0.0f, and q4 = 1.0f, and set the
> R200_TEXGEN_FORCE_W_TO_ONE, thus we can get q to 1.0f. it is OpenGL-compliant!

Maybe I'm missing something, but I fail to see how that can work. If you set
R200_TEXGEN_FORCE_W_TO_ONE how can the result be correct if the incoming vertex
w is != 1.0? I think that basically would just eliminate the w divide which
can't possibly be correct.


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