[Bug 22181] r200: Doom3 engines with r200 renderer (Mesa-7.5-rc3 regression)

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

http://bugs.freedesktop.org/show_bug.cgi?id=22181





--- Comment #5 from Roland Scheidegger <sr...@tu...>  2009-06-10 04:03:40 PST ---
(In reply to comment #4)
> (In reply to comment #2)
> > Created an attachment (id=26606)
 --> (http://bugs.freedesktop.org/attachment.cgi?id=26606) [details] [details]
> > possible fix
> > 
> > No this rather looks like classic z fighting, I think this bug reappeared a
> > couple of times already.
> > Does this patch fix it?
> > I think r100 should also do this though it won't matter for doom3 (and results
> > between fixed function and vertex programs will be different anyway since one
> > will be running in hw one in sw so it might not really help there). (r300
> > probably wants to set this too.)
> > 
> 
> How does dp4/mad selection affect the resulting vertex position?
This affects resulting vertex position only very slightly due to rounding
errors. The reason for z fighting is doom3 renders the same geometry twice,
first pass with fixed function (for shadows), second pass with vertex program.
If the generated fragments don't match z fighting will happen, and since r200
uses DP4 for fixed function hw tcl we need to match that for vertex program.


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