POLYGON3DNORMALANGLE Normal angle at a vertex of the 3D polygon.

   THETA = polygon3DNormalAngle(POLYGON, IND)
   where POLYGON is a set of points, and IND is index of a point in
   polygon. The function compute the angle of the normal cone localized at
   this vertex.
   If IND is a vector of indices, normal angle is computed for each vertex
   specified by IND.

   Example
   % create an equilateral triangle in space
   poly3d = [1 1 0;-1 0 1;0 -1 -1];
   % compute each normal angle
   theta = polygon3dNormalAngle(poly3d, 1:size(poly3d, 1));
   % sum of normal angles must be equal to 2*PI for simple polygons
   sum(theta)

   IMPORTANT NOTE: works only for convex angles ! ! ! !

   See also
   polygons3d, faceNormalAngle

 ------
 Author: David Legland
 e-mail: david.legland@grignon.inra.fr
 Created: 2005-11-30
 Copyright 2005 INRA - CEPIA Nantes - MIAJ (Jouy-en-Josas).

Package: matgeom