GLUTESSNORMAL(3G)														 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 program 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 orien-
       tation 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, 0.0, 0.0) (the initial 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 geom-
       etry.  The  sign  of the normal is chosen so that the sum of the signed areas of all input contours is nonnegative (where a CCW contour has
       positive area).

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

SEE ALSO

       gluTessBeginPolygon, gluTessEndPolygon

																 GLUTESSNORMAL(3G)