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+/*
+ * Copyright (c) 1993-1997, Silicon Graphics, Inc.
+ * ALL RIGHTS RESERVED 
+ * Permission to use, copy, modify, and distribute this software for 
+ * any purpose and without fee is hereby granted, provided that the above
+ * copyright notice appear in all copies and that both the copyright notice
+ * and this permission notice appear in supporting documentation, and that 
+ * the name of Silicon Graphics, Inc. not be used in advertising
+ * or publicity pertaining to distribution of the software without specific,
+ * written prior permission. 
+ *
+ * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
+ * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
+ * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
+ * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
+ * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
+ * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
+ * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
+ * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
+ * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
+ * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
+ * 
+ * US Government Users Restricted Rights 
+ * Use, duplication, or disclosure by the Government is subject to
+ * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
+ * (c)(1)(ii) of the Rights in Technical Data and Computer Software
+ * clause at DFARS 252.227-7013 and/or in similar or successor
+ * clauses in the FAR or the DOD or NASA FAR Supplement.
+ * Unpublished-- rights reserved under the copyright laws of the
+ * United States.  Contractor/manufacturer is Silicon Graphics,
+ * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
+ *
+ * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
+ */
+
+/*
+ *  tess.c
+ *  This program demonstrates polygon tessellation.
+ *  Two tesselated objects are drawn.  The first is a
+ *  rectangle with a triangular hole.  The second is a
+ *  smooth shaded, self-intersecting star.
+ *
+ *  Note the exterior rectangle is drawn with its vertices
+ *  in counter-clockwise order, but its interior clockwise.
+ *  Note the combineCallback is needed for the self-intersecting
+ *  star.  Also note that removing the TessProperty for the 
+ *  star will make the interior unshaded (WINDING_ODD).
+ */
+#include <GL/glut.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#ifdef GLU_VERSION_1_2
+
+/* Win32 calling conventions. */
+#ifndef CALLBACK
+#define CALLBACK
+#endif
+
+GLuint startList;
+
+void display (void) {
+   glClear(GL_COLOR_BUFFER_BIT);
+   glColor3f(1.0, 1.0, 1.0);
+   glCallList(startList);
+   glCallList(startList + 1);
+   glFlush();
+}
+
+void CALLBACK beginCallback(GLenum which)
+{
+   glBegin(which);
+}
+
+void CALLBACK errorCallback(GLenum errorCode)
+{
+   const GLubyte *estring;
+
+   estring = gluErrorString(errorCode);
+   fprintf(stderr, "Tessellation Error: %s\n", estring);
+   exit(0);
+}
+
+void CALLBACK endCallback(void)
+{
+   glEnd();
+}
+
+void CALLBACK vertexCallback(GLvoid *vertex)
+{
+   const GLdouble *pointer;
+
+   pointer = (GLdouble *) vertex;
+   glColor3dv(pointer+3);
+   glVertex3dv(vertex);
+}
+
+/*  combineCallback is used to create a new vertex when edges
+ *  intersect.  coordinate location is trivial to calculate,
+ *  but weight[4] may be used to average color, normal, or texture
+ *  coordinate data.  In this program, color is weighted.
+ */
+void CALLBACK combineCallback(GLdouble coords[3], 
+                     GLdouble *vertex_data[4],
+                     GLfloat weight[4], GLdouble **dataOut )
+{
+   GLdouble *vertex;
+   int i;
+
+   vertex = (GLdouble *) malloc(6 * sizeof(GLdouble));
+
+   vertex[0] = coords[0];
+   vertex[1] = coords[1];
+   vertex[2] = coords[2];
+   for (i = 3; i < 7; i++)
+      vertex[i] = weight[0] * vertex_data[0][i] 
+                  + weight[1] * vertex_data[1][i]
+                  + weight[2] * vertex_data[2][i] 
+                  + weight[3] * vertex_data[3][i];
+   *dataOut = vertex;
+}
+
+void init (void) 
+{
+   GLUtesselator *tobj;
+   GLdouble rect[4][3] = {50.0, 50.0, 0.0,
+                          200.0, 50.0, 0.0,
+                          200.0, 200.0, 0.0,
+                          50.0, 200.0, 0.0};
+   GLdouble tri[3][3] = {75.0, 75.0, 0.0,
+                         125.0, 175.0, 0.0,
+                         175.0, 75.0, 0.0};
+   GLdouble star[5][6] = {250.0, 50.0, 0.0, 1.0, 0.0, 1.0,
+                          325.0, 200.0, 0.0, 1.0, 1.0, 0.0,
+                          400.0, 50.0, 0.0, 0.0, 1.0, 1.0,
+                          250.0, 150.0, 0.0, 1.0, 0.0, 0.0,
+                          400.0, 150.0, 0.0, 0.0, 1.0, 0.0};
+
+   glClearColor(0.0, 0.0, 0.0, 0.0);
+
+   startList = glGenLists(2);
+
+   tobj = gluNewTess();
+   gluTessCallback(tobj, GLU_TESS_VERTEX, 
+                   (GLvoid (CALLBACK*) ()) &glVertex3dv);
+   gluTessCallback(tobj, GLU_TESS_BEGIN, 
+                   (GLvoid (CALLBACK*) ()) &beginCallback);
+   gluTessCallback(tobj, GLU_TESS_END, 
+                   (GLvoid (CALLBACK*) ()) &endCallback);
+   gluTessCallback(tobj, GLU_TESS_ERROR, 
+                   (GLvoid (CALLBACK*) ()) &errorCallback);
+
+   /*  rectangle with triangular hole inside  */
+   glNewList(startList, GL_COMPILE);
+   glShadeModel(GL_FLAT);    
+   gluTessBeginPolygon(tobj, NULL);
+      gluTessBeginContour(tobj);
+         gluTessVertex(tobj, rect[0], rect[0]);
+         gluTessVertex(tobj, rect[1], rect[1]);
+         gluTessVertex(tobj, rect[2], rect[2]);
+         gluTessVertex(tobj, rect[3], rect[3]);
+      gluTessEndContour(tobj);
+      gluTessBeginContour(tobj);
+         gluTessVertex(tobj, tri[0], tri[0]);
+         gluTessVertex(tobj, tri[1], tri[1]);
+         gluTessVertex(tobj, tri[2], tri[2]);
+      gluTessEndContour(tobj);
+   gluTessEndPolygon(tobj);
+   glEndList();
+
+   gluTessCallback(tobj, GLU_TESS_VERTEX, 
+                   (GLvoid (CALLBACK*) ()) &vertexCallback);
+   gluTessCallback(tobj, GLU_TESS_BEGIN, 
+                   (GLvoid (CALLBACK*) ()) &beginCallback);
+   gluTessCallback(tobj, GLU_TESS_END, 
+                   (GLvoid (CALLBACK*) ()) &endCallback);
+   gluTessCallback(tobj, GLU_TESS_ERROR, 
+                   (GLvoid (CALLBACK*) ()) &errorCallback);
+   gluTessCallback(tobj, GLU_TESS_COMBINE, 
+                   (GLvoid (CALLBACK*) ()) &combineCallback);
+
+   /*  smooth shaded, self-intersecting star  */
+   glNewList(startList + 1, GL_COMPILE);
+   glShadeModel(GL_SMOOTH);    
+   gluTessProperty(tobj, GLU_TESS_WINDING_RULE,
+                   GLU_TESS_WINDING_POSITIVE);
+   gluTessBeginPolygon(tobj, NULL);
+      gluTessBeginContour(tobj);
+         gluTessVertex(tobj, star[0], star[0]);
+         gluTessVertex(tobj, star[1], star[1]);
+         gluTessVertex(tobj, star[2], star[2]);
+         gluTessVertex(tobj, star[3], star[3]);
+         gluTessVertex(tobj, star[4], star[4]);
+      gluTessEndContour(tobj);
+   gluTessEndPolygon(tobj);
+   glEndList();
+   gluDeleteTess(tobj);
+}
+
+void reshape (int w, int h)
+{
+   glViewport(0, 0, (GLsizei) w, (GLsizei) h);
+   glMatrixMode(GL_PROJECTION);
+   glLoadIdentity();
+   gluOrtho2D(0.0, (GLdouble) w, 0.0, (GLdouble) h);
+}
+
+/* ARGSUSED1 */
+void keyboard(unsigned char key, int x, int y)
+{
+   switch (key) {
+      case 27:
+         exit(0);
+         break;
+   }
+}
+
+int main(int argc, char** argv)
+{
+   glutInit(&argc, argv);
+   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
+   glutInitWindowSize(500, 500);
+   glutCreateWindow(argv[0]);
+   init();
+   glutDisplayFunc(display);
+   glutReshapeFunc(reshape);
+   glutKeyboardFunc(keyboard);
+   glutMainLoop();
+   return 0;  
+}
+
+#else
+int main(int argc, char** argv)
+{
+    fprintf (stderr, "This program demonstrates the new tesselator API in GLU 1.2.\n");
+    fprintf (stderr, "Your GLU library does not support this new interface, sorry.\n");
+    return 0;
+}
+#endif