OpenGL Programming Guide

Appendix CThe OpenGL Utility Library

Polygon Tessellation

The Tessellation Object

As a complex polygon is being described and tessellated, it has associated data, such as the vertices, edges, and callback functions. All this data is tied to a single tessellation object. To do tessellation, your program first has to create a tessellation object using the routine gluNewTess(). GLUtriangulatorObj* gluNewTess(void);

Creates a new tessellation object and returns a pointer to it. A null pointer is returned if the creation fails.

If you no longer need a tessellation object, you can delete it and free all associated memory with gluDeleteTess(). void gluDeleteTess(GLUtriangulatorObj *tessobj);

Deletes the specified tessellation object, tessobj, and frees all associated memory.

A single tessellation object can be reused for all your tessellations. This object is required only because library routines might need to do their own tessellations, and they should be able to do so without interfering with any tessellation that your program is doing. It might also be useful to have multiple tessellation objects if you want to use different sets of callbacks for different tessellations. A typical program, however, allocates a single tessellation object and uses it for all its tessellations. There's no real need to free it because it uses a small amount of memory. On the other hand, if you're writing a library routine that uses the GLU tessellation, you'll want to be careful to free any tessellation objects you create.

OpenGL Programming Guide