[quote="Ashley":1o65s6rr]Yeah you could do it by compositing convex polygons, but not a single concave polygon on its own. I don't think Ellipse in the physics engine uses vertices at all, I suspect it's a custom algorithm, since there are probably specific equations for perfectly round objects.
The reason is (not that I'm an expert) that it's much harder to write an efficient collision detection engine if you can't guarantee a convex polygon. I'm not sure the specifics why. I think it also applies to a dynamic shadows engine, but I'm not sure.[/quote:1o65s6rr]
Perhaps what's needed is an algorithm to automagically convert complex polys to tris, the way 3D modelling programs do:
Programs like Max and Maya let you make crazy n-sided polygons, but blow the surface it's all converted to triangles.