note
bart
There's a nice simple algorithm to check if a point is inside a polygon: the principle is this: draw a line from it to any point outside the polygon (for example with an X that is larger than any X for all the polygon vertices), and count how many edges it crosses. Iff this number is even, the point is outside of the polygon.
<P>There are problematic cases where your test line goes straight through a vertex. You could think up an elaborate advanced scheme, taking the direction of the crossing into account, and counting such a crossing as +0.5 or -0.5 depending on its direction; or you could simply try again with a different line.
<P>Combine this with tests on whether any edges from the polygons actually cross, and the basis is set.
402017
402017