DIHEDRALANGLE Compute dihedral angle between 2 planes.

   THETA = dihedralAngle(PLANE1, PLANE2)
   PLANE1 and PLANE2 are plane representations given in the following
   format:
   [x0 y0 z0 dx1 dy1 dz1 dx2 dy2 dz2]
   THETA is the angle between the two vectors given by plane normals,
   given between 0 and PI.

   References
   http://en.wikipedia.org/wiki/Dihedral_angle
   http://mathworld.wolfram.com/DihedralAngle.html

   See also:
   planes3d, lines3d, angles3d, planesBisector

   ---------
   author : David Legland 
   INRA - TPV URPOI - BIA IMASTE
   created the 21/02/2005.

Package: matgeom