1GLUTESSVERTEX(3G)                OpenGL Manual               GLUTESSVERTEX(3G)
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NAME

6       gluTessVertex - specify a vertex on a polygon
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C SPECIFICATION

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

13       tess
14           Specifies the tessellation object (created with gluNewTess()).
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16       location
17           Specifies the location of the vertex.
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19       data
20           Specifies an opaque pointer passed back to the program with the
21           vertex callback (as specified by gluTessCallback()).
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DESCRIPTION

24       gluTessVertex describes a vertex on a polygon that the program defines.
25       Successive gluTessVertex calls describe a closed contour. For example,
26       to describe a quadrilateral, gluTessVertex should be called four times.
27       gluTessVertex can only be called between gluTessBeginContour() and
28       gluTessEndContour().
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30       data normally points to a structure containing the vertex location, as
31       well as other per-vertex attributes such as color and normal. This
32       pointer is passed back to the user through the GLU_TESS_VERTEX or
33       GLU_TESS_VERTEX_DATA callback after tessellation (see the
34       gluTessCallback() reference page).
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EXAMPLE

37       A quadrilateral with a triangular hole in it can be described as
38       follows:
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40           gluTessBeginPolygon(tobj, NULL);
41              gluTessBeginContour(tobj);
42                 gluTessVertex(tobj, v1, v1);
43                 gluTessVertex(tobj, v2, v2);
44                 gluTessVertex(tobj, v3, v3);
45                 gluTessVertex(tobj, v4, v4);
46              gluTessEndContour(tobj);
47              gluTessBeginContour(tobj);
48                 gluTessVertex(tobj, v5, v5);
49                 gluTessVertex(tobj, v6, v6);
50                 gluTessVertex(tobj, v7, v7);
51              gluTessEndContour(tobj);
52           gluTessEndPolygon(tobj);
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NOTES

57       It is a common error to use a local variable for location or data and
58       store values into it as part of a loop. For example:
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60           for (i = 0; i < NVERTICES; ++i) {
61              GLdouble data[3];
62              data[0] = vertex[i][0];
63              data[1] = vertex[i][1];
64              data[2] = vertex[i][2];
65              gluTessVertex(tobj, data, data);
66           }
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69       This doesn't work. Because the pointers specified by location and data
70       might not be dereferenced until gluTessEndPolygon() is executed, all
71       the vertex coordinates but the very last set could be overwritten
72       before tessellation begins.
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74       Two common symptoms of this problem are when the data consists of a
75       single point (when a local variable is used for data) and a
76       GLU_TESS_NEED_COMBINE_CALLBACK error (when a local variable is used for
77       location).
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SEE ALSO

80       gluNewTess(), gluTessBeginContour(), gluTessBeginPolygon(),
81       gluTessCallback(), gluTessEndPolygon(), gluTessNormal(),
82       gluTessProperty()
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85       Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
86       under the SGI Free Software B License. For details, see
87       http://oss.sgi.com/projects/FreeB/.
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AUTHORS

90       opengl.org
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94opengl.org                        06/10/2014                 GLUTESSVERTEX(3G)
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