Each 3D object is described by two files --
one that specifies the vertices,
and the other that specifies how the vertices are connected to form
polygons.

(a) coor file -- coordinate file specifies the coordinates of vertices.
	line 1:  number of vertices.
	line 2..n+1: list the x,y,z coordinates of the n points

(b) poly file -- polygon file.
	line 1:  number of polygons
	line 2..n+1: list of vertices for each polygon.  first column is just
		a label for the polygon.  the first and last vertices are
		connected to form a closed polygon.