** Next:** Experiments and Results
** Up:** Contents
** Previous:** SGI-based Algorithm Implementation

While using the OpenGL library, some other speed-up improvements
could be done. Few years ago, new extensions had been added to
OpenGL system. These extensions are working with vertex arrays and
indices to these arrays. If not using these extensions, three
vertices (3*3 coordinates) are needed to define each triangle. For
two triangles 3*3*2 coordinates are needed, etc. In fact, the
vertex coordinates are shared by more than one triangle (e.g.,in
Delaunay triangulation one vertex is shared by approximately 6
triangles). The reduced data size should be twice smaller than the
original size. Original size is *t * 3 vertices * 3 coordinates = 9 * t*,
while reduced size is *v * 3 coordinates + t * 3 indices*,
where *t* is the number of triangles and *v* is the
number of vertices. Because in a usual triangle model the number
of vertices is about twice smaller than the number of triangles,
the reduced size is *(t/2) * 3 + t * 3 = 9 * t/2*.
It's also possible to use these extensions in combination with
triangle strips. The reduced data size while using triangle strips
and OpenGL extension should be about 6 times smaller than the
classic method (three times smaller using triangle strips and
twice smaller using the extension).

Petr Vanecek, pet@students.zcu.cz,
2002-03-19