gluTessNormal()                                   gluTessNormal()

NAME    [Toc]    [Back]

       gluTessNormal - specify a normal for a polygon

SYNOPSIS    [Toc]    [Back]

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

PARAMETERS    [Toc]    [Back]

       Specifies  the  tessellation object (created with gluNewTess()).
  Specifies the  first  component  of  the  normal.
       Specifies  the  second component of the normal.  Specifies
       the third component of the normal.

DESCRIPTION    [Toc]    [Back]

       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    [Toc]    [Back]

       gluTessBeginPolygon(3), gluTessEndPolygon(3)



                                                  gluTessNormal()