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From: teunis <teunis@computersupportcentre.com>
To : ggi-develop@eskimo.com
Date: Wed, 19 Aug 1998 19:29:23 -0700 (MST)
Re: LibGGI3D RFC
On Wed, 19 Aug 1998, Jon M. Taylor wrote:
> 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.
No it doesn't. Not if you forget the other info present. A normal won't
interpolate a texture coordinate. Or a colour coordinate if you do
colour-shading across a texture. Or other more bizarre data (ie: mixing
coefficient for mixing two textures :)
G'day, eh? :)
- Teunis
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