gluTessBeginPolygon function

The gluTessBeginPolygon and gluTessEndPolygon functions delimit a polygon description.

Syntax

void WINAPI gluTessBeginPolygon(
   GLUtesselator *tess,
   void          *polygon_data
);

Parameters

tess

The tessellation object (created with gluNewTess).

polygon_data

A pointer to a programmer-defined polygon data structure.

Return value

This function does not return a value.

Remarks

The gluTessBeginPolygon and gluTessEndPolygon functions delimit the definition of a nonconvex polygon. Within each gluTessBeginPolygon / gluTessEndPolygon pair, include one or more calls to gluTessBeginContour. Within each contour, there are zero or more calls to gluTessVertex. The vertexes specify a closed contour (the last vertex of each contour is automatically linked to the first).

The polygon_data parameter is a pointer to a programmer-defined data structure. If the appropriate callbacks are specified (see gluTessCallback), this pointer is returned to the callback function or functions, making it a convenient way to store per-polygon information.

When you call gluTessEndPolygon, the polygon is tessellated, and the resulting triangles are described through callbacks. For descriptions of the callback functions, see gluTessCallback.

Examples

The following describes a quadrilateral with a triangular hole:

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);

Requirements

See also

gluNewTess

gluTessBeginContour

gluTessCallback

gluTessEndContour

gluTessNormal

gluTessProperty

gluTessVertex