gluTessBeginPolygon — delimit a polygon description
void gluTessBeginPolygon( | GLUtesselator* | tess, |
| GLvoid* | data); |
tessSpecifies the tessellation object (created with gluNewTess).
dataSpecifies a pointer to user polygon data.
gluTessBeginPolygon and gluTessEndPolygon delimit the definition of a
convex, concave or self-intersecting 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.
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.
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);
gluNewTess, gluTessBeginContour, gluTessCallback, gluTessEndPolygon, gluTessNormal, gluTessProperty, gluTessVertex
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