Re: Inside or outside of a polyhedron

["Andrzej Szymoszek" <ASZYM \\at// ichuwr.chem.uni.wroc.pl>]

   Dear Netters,
   Shouldn't be noticed that if you have n points in space, it isn't
  determined what kind of polyhedron you actually have? This is the
  non-convex case. Imagine 4 points in 2D:
                            .4
                           3.
                        1.      2.
   You can go 1-2-4-3-1, or 1-3-4-2-1, or 1-3-2-4-1. So the problem is
  in this case quite complicated.
   For the "convex" case, staying by 2D (generalization to 3D is
  straightforward, hopefully :-) I have an idea first to find a gravity
  centre of the polygon. This is the point we are sure it is inside.
  Then you join g.c. with the point in question- and determine whether
  it crosses the border (point outside) or not (inside).
   Andrzej Szymoszek
   aszym \\at// ichuwr.chem.uni.wroc.pl