gluTessNormal

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 orienta-
       tion  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(3G), gluTessEndPolygon(3G)






							    GLUTESSNORMAL(3G)