GLUTESSVERTEX(3G)						   OpenGL Manual						 GLUTESSVERTEX(3G)

NAME

       gluTessVertex - specify a vertex on a polygon

C SPECIFICATION

       void gluTessVertex(GLUtesselator* tess, GLdouble * location, GLvoid* data);

PARAMETERS

       tess
	   Specifies the tessellation object (created with gluNewTess()).

       location
	   Specifies the location of the vertex.

       data
	   Specifies an opaque pointer passed back to the program with the vertex callback (as specified by gluTessCallback()).

DESCRIPTION

       gluTessVertex describes a vertex on a polygon that the program defines. Successive gluTessVertex calls describe a closed contour. For
       example, to describe a quadrilateral, gluTessVertex should be called four times.  gluTessVertex can only be called between
       gluTessBeginContour() and gluTessEndContour().

       data normally points to a structure containing the vertex location, as well as other per-vertex attributes such as color and normal. This
       pointer is passed back to the user through the GLU_TESS_VERTEX or GLU_TESS_VERTEX_DATA callback after tessellation (see the
       gluTessCallback() reference page).

EXAMPLE

       A quadrilateral with a triangular hole in it can be described as follows:

	   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);

NOTES

       It is a common error to use a local variable for location or data and store values into it as part of a loop. For example:

	   for (i = 0; i < NVERTICES; ++i) {
	      GLdouble data[3];
	      data[0] = vertex[i][0];
	      data[1] = vertex[i][1];
	      data[2] = vertex[i][2];
	      gluTessVertex(tobj, data, data);
	   }

       This doesn't work. Because the pointers specified by location and data might not be dereferenced until gluTessEndPolygon() is executed, all
       the vertex coordinates but the very last set could be overwritten before tessellation begins.

       Two common symptoms of this problem are when the data consists of a single point (when a local variable is used for data) and a
       GLU_TESS_NEED_COMBINE_CALLBACK error (when a local variable is used for location).

SEE ALSO

       gluNewTess(), gluTessBeginContour(), gluTessBeginPolygon(), gluTessCallback(), gluTessEndPolygon(), gluTessNormal(), gluTessProperty()

COPYRIGHT

       Copyright (C) 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see
       http://oss.sgi.com/projects/FreeB/.

AUTHORS

       opengl.org

opengl.org							    06/10/2014							 GLUTESSVERTEX(3G)