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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 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, 0.0, 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  geometry.  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)