Clipping a Triangle Polygon: The best way ???

Clipping a Triangle Polygon: The best way ???

Post by Steve Humphrie » Tue, 22 Jul 1997 04:00:00

> Hi, I am searching for information on the best polygon clipping
> routine.

> At present I am trying the two most common, Sutherland-Hodgman
> reentrant

> and Laing-Barsky parametric.

> The problem I have is that when clipping in a corner, the clipper does

> not clip my
> UV coords for the corner. How do I clip a tri-poly and generate a
> corner
> vertex
> with the correct UV information ???

> Also, Once clipped, I require triangles as the return, and not a 4-5-6

> sided poly.
> I wish to pass these into a pure triangle renderer, so only triangles
> can be output
> by the clipper.

> I have had no success in finding a complete routine, source or
> otherwise.
> This is a fundemantal part of a renderer but there seems to be a
> severe
> lack of
> references out there.

> Any help will be much appreciated !

> Cheers


1. Converting polygons to triangles after clipping

I am currently rewriting my renderer to use triangles only instead of
arbitrary size polygons. The reasons are various, but my question is:

After clipping a triangle in screen space against a rectangular boundary,
the resulting polygon is no longer a triangle. Is there an efficient way
to divide this polygon back into triangles? If yes, how.

Fabian Gonzalez


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