[comp.graphics] Help with Painter's algorithm for non-intersecting polygons

butch@fergvax.unl.edu (FERGVAX Daily Operator) (06/26/91)

	I'm working on a polygon-based 3D graphing application and I need a good
sorting algorithm for the faces.  I've worked with just sorting on a Z value
(which I know doesn't work, but was enough to show my off the program at the
time) and I've looked in Foley-Van Damm at the Newell-Newell-Sanchez
algorithm.  The latter I like and it's precisely what I'm looking for.
However, I'm stuck:

	So, I've got some questions:  (1) How can you tell if one polygon is
completely on a one side of another polygon, and (2) There are cases where
adding a test for (1) does not completely insure a correctly sorted face list,
so could anyone recommend some extra criteria for correctly sorting
non-intersecting polygons?

Please e-mail me at butch@fergvax.unl.edu if you can help me.

Thanks in advance,

Butch