gluTessBeginPolygon
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## Name

gluTessBeginPolygon — delimit a polygon description

## C Specification

`void `gluTessBeginPolygon`` | `(` | `GLUtesselator* `tess`, GLvoid* `data`);`

## Python Specification

``gluTessBeginPolygon`` | `(` | ``tess`, `data`) → `None``

## 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

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