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, May 26, 1995

AFV