Intersections with polygons

Projecting the polygon and the intersection point:

choose the axis for which the normal component

is maximal, and project to the plane perpendicular

to that axis; for example, if x component is maximal

then project to yz. Projection is achieved by discarding

on coordinate (x in the example).

A convex polygon can be

thought of as an intersection

of a set of half planes.

(Note: all vertices are 2D now!

we discarded one coordinate).