GLUTESSBEGINPOLYGON(3G) manual page

Table of Contents

## Name

gluTessBeginPolygon - delimit a polygon description

## C Specification

void gluTessBeginPolygon( GLUtesselator* tess,

        GLvoid* data )

eqn not supported

## Parameters

tess
  Specifies the tessellation object (created with gluNewTess).
data
  Specifies a pointer to user polygon data.

## Description

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.

## 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);

## See Also

gluNewTess, gluTessBeginContour, gluTessVertex, gluTessCallback, gluTessProperty, gluTessNormal, gluTessEndPolygon

Table of Contents

- Name
- C Specification
- Parameters
- Description
- Example
- See Also