From: Jon M. Taylor <taylorj@ecs.csus.edu>
  To  : ggi-develop@eskimo.com
  Date: Wed, 19 Aug 1998 18:55:09 -0700 (PDT)

Re: LibGGI3D RFC

On Thu, 20 Aug 1998, Olivier Galibert wrote:

> On Wed, Aug 19, 1998 at 05:18:05PM -0700, Jon M. Taylor wrote:
> > 	The higher layers could clip during tesellation, and as such
> > they'd be able to take all those coordinates into account.
> 
> By "clip" do you mean 2d clipping?  

	No.  Yes.  Maybe |->.  It depends on how you clip.  You *could*
have your 3D clipper turn partially-visible triangles into two triangles
and do HSR and backface culling, so that when the triangles are sent to
LibGGI3D for drawing there are no z-overlaps or clipping issues left. 

> If yes, wouldn't that break gouraud shading?

	Not if you do it right.  If the clipper described above were to
interpolate the vertex normals of the pre-clipped triangle along the two
clipped sides, it could compute the effective vertex normals of the two
new triangle vertices which would be created by the clip.  This allows you
to get the exact same effective shading.

Jon

---
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