This function generates a new surface point, P and a new 
surface normal, N.  The reflection vector R is also calculated.
P and N are new globals which are returned to the renderer 
and used by any surface shader following this displacement.
PP  is the point to be displaced.
DIR is the direction vector for the displacement.
AMP is the amplitude of the displacement.
VAL is the displacement value.

This must be a point.  The default is is the surface point, P.
This is the point to be displaced.

This must be a normal.  The default is is the surface normal, N.
This is the direction vector for the displacement.

This must be a float.  The default is 0.05.
This is the amplitude of the displacement.

This must be a float.  The default is 0.0.
This is the displacement value.

This is the new shading normal.

This is the new reflection vector.

This is the new surface point.