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#include <windows.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <stdlib.h>
#include <stdio.h>
#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,
glVertex3dv);
gluTessCallback(tobj, GLU_TESS_BEGIN,
beginCallback);
gluTessCallback(tobj, GLU_TESS_END,
endCallback);
gluTessCallback(tobj, GLU_TESS_ERROR,
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,
vertexCallback);
gluTessCallback(tobj, GLU_TESS_BEGIN,
beginCallback);
gluTessCallback(tobj, GLU_TESS_END,
endCallback);
gluTessCallback(tobj, GLU_TESS_ERROR,
errorCallback);
gluTessCallback(tobj, GLU_TESS_COMBINE,
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);
}
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;
} |
