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GLUTESSVERTEX()						       GLUTESSVERTEX()

NAME
       gluTessVertex - specify a vertex	on a polygon

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

       delim $$

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 gluTessCall-
       back reference page).

EXAMPLE
       A quadrilateral with a triangular hole in it can	be described  as  fol-
       lows:

       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	consists  of  a	 single	 point
       (when  a	 local	variable  is  used  for	data) and a GLU_TESS_NEED_COM-
       BINE_CALLBACK error (when a local variable is used for location).

SEE ALSO
       gluTessBeginPolygon, gluNewTess,	gluTessBeginContour,  gluTessCallback,
       gluTessProperty,	gluTessNormal, gluTessEndPolygon

							       GLUTESSVERTEX()

NAME | C SPECIFICATION | PARAMETERS | DESCRIPTION | EXAMPLE | NOTES | SEE ALSO

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