gluTessNormal(3G)	       OpenGL Reference		     gluTessNormal(3G)



NAME
     gluTessNormal - specify a normal for a polygon


C SPECIFICATION
     void gluTessNormal( GLUtesselator*	tess,
			 GLdouble valueX,
			 GLdouble valueY,
			 GLdouble valueZ )


PARAMETERS
     tess    Specifies the tessellation	object (created	with gluNewTess).

     valueX  Specifies the first component of the normal.

     valueY  Specifies the second component of the normal.

     valueZ  Specifies the third component of the normal.


DESCRIPTION
     gluTessNormal describes a normal for a polygon that the user is defining.
     All input data will be projected onto a plane perpendicular to one	of the
     three coordinate axes before tessellation and all output triangles	will
     be	oriented CCW with respect to the normal	(CW orientation	can be
     obtained by reversing the sign of the supplied normal). For example, if
     you know that all polygons	lie in the x-y plane, call gluTessNormal(tess,
     0.0, 0.0, 1.0) before rendering any polygons.

     If	the supplied normal is (0,0,0) (the default value), the	normal is
     determined	as follows. The	direction of the normal, up to its sign, is
     found by fitting a	plane to the vertices, without regard to how the
     vertices are connected. It	is expected that the input data	lies
     approximately in the plane; otherwise projection perpendicular to one of
     the three coordinate axes may substantially change	the geometry. The sign
     of	the normal is chosen so	that the sum of	the signed areas of all	input
     contours is non-negative (where a CCW contour has positive	area).

     The supplied normal persists until	it is changed by another call to
     gluTessNormal.


SEE ALSO
     gluTessBeginPolygon, gluTessEndPolygon










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