Re: polygons question

makc.the.great@xxxxxxxxx wrote: 
suppose there are lots of polygons, z-ordered. how do you find if
particular polygon is visible?

that is, how do you check that an edge (line segment) lies within an
area covered by several polygons?

I was thinking about "collapsing" all foregound polygons into one union
shape, then you could just check one vertex and intersections with its
edges; but 1 how do I find union 2 is there better way?

IMHO you should seriously consider reading some introductory material on computer graphics computations first. I recommend the standard book, Computer Graphics: Principles and Practice (Foley, van Dam, Feiner & Hughes). There are too many approaches to solving your problem to post here.
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