wumpus-basic

Copperbox revision 1547.

A better prototype than yesterday's effort to find the intersection of a point and a plane (and hence a calculate radial anchors).

Today's version has a problem though - because it finds the intersection of a line segment and a plane it is insensitive to the "correct" quadrant. E.g. the plane for the east and west anchors is the same - the horizontal plane - and polygon crosses the horizontal plane at both east and west. Calculating "west" actually finds east because of the search order of the polygon's line segments.