From http://www.jwz.org/xscreensaver/xscreensaver-5.27.tar.gz

[xscreensaver] / hacks / delaunay.h

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+/* Triangulate
+   Efficient Triangulation Algorithm Suitable for Terrain Modelling
+   or
+   An Algorithm for Interpolating Irregularly-Spaced Data
+   with Applications in Terrain Modelling
+
+   Written by Paul Bourke
+   Presented at Pan Pacific Computer Conference, Beijing, China.
+   January 1989
+   Abstract
+
+   A discussion of a method that has been used with success in terrain
+   modelling to estimate the height at any point on the land surface
+   from irregularly distributed samples. The special requirements of
+   terrain modelling are discussed as well as a detailed description
+   of the algorithm and an example of its application.
+
+   http://paulbourke.net/papers/triangulate/
+   http://paulbourke.net/papers/triangulate/triangulate.c
+ */
+
+#ifndef __DELAUNAY_H__
+#define __DELAUNAY_H__
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif /* HAVE_CONFIG_H */
+
+typedef struct {
+   double x,y,z;
+} XYZ;
+
+typedef struct {
+   int p1,p2,p3;
+} ITRIANGLE;
+
+/*
+   Takes as input NV vertices in array pxyz
+   Returned is a list of ntri triangular faces in the array v
+   These triangles are arranged in a consistent clockwise order.
+   The triangle array 'v' should be malloced to 3 * nv
+   The vertex array pxyz must be big enough to hold 3 more points
+   The vertex array must be sorted in increasing x values
+ */
+extern int delaunay (int nv, XYZ *pxyz, ITRIANGLE *v, int *ntri);
+
+/* qsort(p,nv,sizeof(XYZ), delaunay_xyzcompare); */
+extern int delaunay_xyzcompare (const void *v1, const void *v2);
+
+
+#endif /* __DELAUNAY_H__ */
+