gluTessBeginPolygon.3gl (GLU version 1.2 and later)

Name

  gluTessBeginPolygon -	delimit	a polygon description

C Specification

  void gluTessBeginPolygon( GLUtesselator *tess,
			    void *polygon_data )

Parameters

  tess		Specifies the tessellation object (created with	gluNewTess).

  polygon_data	Specifies a pointer to user polygon data.

Description

  gluTessBeginPolygon and gluTessEndPolygon delimit the	definition of a
  nonconvex polygon. Within each gluTessBeginPolygon/gluTessEndPolygon pair,
  there	must be	one or more calls to gluTessBeginContour/gluTessEndContour.
  Within each contour, there are zero or more calls to gluTessVertex. The
  vertices specify a closed contour (the last vertex of	each contour is
  automatically	linked to the first).  See the gluTessVertex,
  gluTessBeginContour and gluTessEndContour reference pages for	more details.

  polygon_data is a pointer to a user-defined data structure. If the
  appropriate callback(s) are specified	(see gluTessCallback), then this
  pointer is returned to the callback function(s). Thus, it is a convenient
  way to store per-polygon information.

  Once gluTessEndPolygon is called, the	polygon	is tessellated,	and the
  resulting triangles are described through callbacks.	See gluTessCallback
  for descriptions of the callback functions.

Example

  A quadrilateral with a triangular hole in it can be described	like this:

  gluTessBeginPolygon(tobj, NULL);
   gluTessBeginContour(tobj);
     gluTessVertex(tobj, v1, v1);
     gluTessVertex(tobj, v2, v2);
     gluTessVertex(tobj, v3, v3);
     gluTessVertex(tobj, v4, v4);
   gluTessEndContour(tobj);
   gluTessBeginContour(tobj);
     gluTessVertex(tobj, v5, v5);
     gluTessVertex(tobj, v6, v6);
     gluTessVertex(tobj, v7, v7);
   gluTessEndContour(tobj);
  gluTessEndPolygon(tobj);

See Also

  gluNewTess, gluTessBeginContour, gluTessVertex, gluTessCallback,
  gluTessProperty, gluTessNormal gluTessEndPolygon

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Last Edited: Fri Dec 6 11:18:03 EST 1996 by AFV
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