RE: clipping planes bypassed in CG vertex shaders

"Tony Cox" <[email protected]>
Newsgroups gmane.games.devel.opengl
Organization Fat City Network Services, San Diego, California
Message-ID <[email protected]>
No, as previously explained by others, there's just no way you can possibly clip before the vertex shader. Since the final position of the vertex is computed by it, how would you know whether and how to clip until you've run it?

Tony Cox - Development Manager
Studio ZR, Microsoft Game Studios

-----Original Message-----
Sent: Monday, May 23, 2005 8:03 PM
To: Multiple recipients of list OPENGL-GAMEDEV-L

Guys, thanks for all comments.

Well, clipping must be applied per primitive (i.e. triangle)... so, it could 
be done before shading... Primitives can be removed, or clipped (it could 
add new verteces). So, in vertex shader, we can receive unclipped or new 
verteces, and we can play with them as we need (modify: move, translate, 
whatever). I think, it is good.

After vertex shader, clipping even works, but it could not be good enough, 
because we do not want to waste gpu time shading verteces of objects which 
are going to be removed by clipping.

Well, anyway, the point is that user clipping planes are disable in 
programmable pipeline (at least in my fx5200 and fx6800). I think, it is a 
little damn for some programmers.

Regards
Rhadamés

ibing).
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-- 
Author: Tony Cox
  INET: [email protected]

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