Index for Section 3

Alphabetical listing for G

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gluTessNormal()
NAME
  gluTessNormal - specify a normal for a polygon

SYNOPSIS
  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(3), gluTessEndPolygon(3)

Index for Section 3

Alphabetical listing for G

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