525 lines
11 KiB
C
525 lines
11 KiB
C
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/*
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* A demo of the GLU polygon tesselation functions written by Bogdan Sikorski.
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* Updated for GLU 1.3 tessellation by Gareth Hughes <gareth@valinux.com>
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <GL/glut.h>
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#define MAX_POINTS 256
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#define MAX_CONTOURS 32
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#define MAX_TRIANGLES 256
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#ifndef GLCALLBACK
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#ifdef CALLBACK
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#define GLCALLBACK CALLBACK
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#else
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#define GLCALLBACK
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#endif
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#endif
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#ifdef GLU_VERSION_1_2
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typedef enum{ QUIT, TESSELATE, CLEAR } menu_entries;
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typedef enum{ DEFINE, TESSELATED } mode_type;
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static GLsizei width, height;
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static GLuint contour_cnt;
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static GLuint triangle_cnt;
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static mode_type mode;
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static int menu;
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static GLuint list_start;
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static GLfloat edge_color[3];
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static struct {
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GLfloat p[MAX_POINTS][2];
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GLuint point_cnt;
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} contours[MAX_CONTOURS];
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static struct {
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GLsizei no;
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GLfloat p[3][2];
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GLclampf color[3][3];
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} triangles[MAX_TRIANGLES];
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static void GLCALLBACK error_callback( GLenum err )
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{
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int len, i;
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char const *str;
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glColor3f( 0.9, 0.9, 0.9 );
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glRasterPos2i( 5, 5 );
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str = (const char *) gluErrorString( err );
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len = strlen( str );
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for ( i = 0 ; i < len ; i++ ) {
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glutBitmapCharacter( GLUT_BITMAP_9_BY_15, str[i] );
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}
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}
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static void GLCALLBACK begin_callback( GLenum mode )
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{
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/* Allow multiple triangles to be output inside the begin/end pair. */
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triangle_cnt = 0;
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triangles[triangle_cnt].no = 0;
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}
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static void GLCALLBACK edge_callback( GLenum flag )
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{
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/* Persist the edge flag across triangles. */
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if ( flag == GL_TRUE ) {
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edge_color[0] = 1.0;
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edge_color[1] = 1.0;
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edge_color[2] = 0.5;
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} else {
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edge_color[0] = 1.0;
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edge_color[1] = 0.0;
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edge_color[2] = 0.0;
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}
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}
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static void GLCALLBACK end_callback()
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{
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GLuint i;
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glBegin( GL_LINES );
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/* Output the three edges of each triangle as lines colored
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according to their edge flag. */
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for ( i = 0 ; i < triangle_cnt ; i++ ) {
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glColor3f( triangles[i].color[0][0],
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triangles[i].color[0][1],
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triangles[i].color[0][2] );
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glVertex2f( triangles[i].p[0][0], triangles[i].p[0][1] );
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glVertex2f( triangles[i].p[1][0], triangles[i].p[1][1] );
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glColor3f( triangles[i].color[1][0],
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triangles[i].color[1][1],
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triangles[i].color[1][2] );
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glVertex2f( triangles[i].p[1][0], triangles[i].p[1][1] );
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glVertex2f( triangles[i].p[2][0], triangles[i].p[2][1] );
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glColor3f( triangles[i].color[2][0],
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triangles[i].color[2][1],
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triangles[i].color[2][2] );
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glVertex2f( triangles[i].p[2][0], triangles[i].p[2][1] );
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glVertex2f( triangles[i].p[0][0], triangles[i].p[0][1] );
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}
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glEnd();
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}
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static void GLCALLBACK vertex_callback( void *data )
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{
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GLsizei no;
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GLfloat *p;
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p = (GLfloat *) data;
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no = triangles[triangle_cnt].no;
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triangles[triangle_cnt].p[no][0] = p[0];
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triangles[triangle_cnt].p[no][1] = p[1];
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triangles[triangle_cnt].color[no][0] = edge_color[0];
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triangles[triangle_cnt].color[no][1] = edge_color[1];
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triangles[triangle_cnt].color[no][2] = edge_color[2];
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/* After every three vertices, initialize the next triangle. */
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if ( ++(triangles[triangle_cnt].no) == 3 ) {
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triangle_cnt++;
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triangles[triangle_cnt].no = 0;
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}
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}
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static void GLCALLBACK combine_callback( GLdouble coords[3],
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GLdouble *vertex_data[4],
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GLfloat weight[4], void **data )
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{
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GLfloat *vertex;
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vertex = (GLfloat *) malloc( 2 * sizeof(GLfloat) );
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vertex[0] = (GLfloat) coords[0];
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vertex[1] = (GLfloat) coords[1];
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*data = vertex;
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}
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static void set_screen_wh( GLsizei w, GLsizei h )
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{
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width = w;
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height = h;
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}
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typedef void (GLAPIENTRY *callback_t)();
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static void tesse( void )
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{
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GLUtesselator *tobj;
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GLdouble data[3];
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GLuint i, j, point_cnt;
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list_start = glGenLists( 2 );
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tobj = gluNewTess();
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if ( tobj != NULL ) {
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gluTessNormal( tobj, 0.0, 0.0, 1.0 );
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gluTessCallback( tobj, GLU_TESS_BEGIN, (callback_t) glBegin );
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gluTessCallback( tobj, GLU_TESS_VERTEX, (callback_t) glVertex2fv );
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gluTessCallback( tobj, GLU_TESS_END, (callback_t) glEnd );
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gluTessCallback( tobj, GLU_TESS_ERROR, (callback_t) error_callback );
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gluTessCallback( tobj, GLU_TESS_COMBINE, (callback_t) combine_callback );
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glNewList( list_start, GL_COMPILE );
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gluBeginPolygon( tobj );
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for ( j = 0 ; j <= contour_cnt ; j++ ) {
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point_cnt = contours[j].point_cnt;
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gluNextContour( tobj, GLU_UNKNOWN );
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for ( i = 0 ; i < point_cnt ; i++ ) {
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data[0] = (GLdouble)( contours[j].p[i][0] );
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data[1] = (GLdouble)( contours[j].p[i][1] );
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data[2] = 0.0;
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gluTessVertex( tobj, data, contours[j].p[i] );
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}
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}
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gluEndPolygon( tobj );
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glEndList();
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gluTessCallback( tobj, GLU_TESS_BEGIN, (callback_t) begin_callback );
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gluTessCallback( tobj, GLU_TESS_VERTEX, (callback_t) vertex_callback );
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gluTessCallback( tobj, GLU_TESS_END, (callback_t) end_callback );
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gluTessCallback( tobj, GLU_TESS_EDGE_FLAG, (callback_t) edge_callback );
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glNewList( list_start + 1, GL_COMPILE );
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gluBeginPolygon( tobj );
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for ( j = 0 ; j <= contour_cnt ; j++ ) {
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point_cnt = contours[j].point_cnt;
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gluNextContour( tobj, GLU_UNKNOWN );
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for ( i = 0 ; i < point_cnt ; i++ ) {
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data[0] = (GLdouble)( contours[j].p[i][0] );
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data[1] = (GLdouble)( contours[j].p[i][1] );
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data[2] = 0.0;
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gluTessVertex( tobj, data, contours[j].p[i] );
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}
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}
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gluEndPolygon( tobj );
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glEndList();
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gluDeleteTess( tobj );
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glutMouseFunc( NULL );
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mode = TESSELATED;
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}
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}
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static void left_down( int x1, int y1 )
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{
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GLfloat P[2];
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GLuint point_cnt;
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/* translate GLUT into GL coordinates */
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P[0] = x1;
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P[1] = height - y1;
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point_cnt = contours[contour_cnt].point_cnt;
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contours[contour_cnt].p[point_cnt][0] = P[0];
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contours[contour_cnt].p[point_cnt][1] = P[1];
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glBegin( GL_LINES );
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if ( point_cnt ) {
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glVertex2fv( contours[contour_cnt].p[point_cnt-1] );
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glVertex2fv( P );
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} else {
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glVertex2fv( P );
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glVertex2fv( P );
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}
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glEnd();
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glFinish();
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contours[contour_cnt].point_cnt++;
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}
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static void middle_down( int x1, int y1 )
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{
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GLuint point_cnt;
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(void) x1;
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(void) y1;
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point_cnt = contours[contour_cnt].point_cnt;
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if ( point_cnt > 2 ) {
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glBegin( GL_LINES );
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glVertex2fv( contours[contour_cnt].p[0] );
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glVertex2fv( contours[contour_cnt].p[point_cnt-1] );
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contours[contour_cnt].p[point_cnt][0] = -1;
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glEnd();
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glFinish();
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contour_cnt++;
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contours[contour_cnt].point_cnt = 0;
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}
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}
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static void mouse_clicked( int button, int state, int x, int y )
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{
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x -= x%10;
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y -= y%10;
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switch ( button ) {
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case GLUT_LEFT_BUTTON:
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if ( state == GLUT_DOWN ) {
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left_down( x, y );
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}
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break;
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case GLUT_MIDDLE_BUTTON:
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if ( state == GLUT_DOWN ) {
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middle_down( x, y );
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}
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break;
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}
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}
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static void display( void )
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{
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GLuint i,j;
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GLsizei ii, jj;
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GLuint point_cnt;
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glClear( GL_COLOR_BUFFER_BIT );
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switch ( mode ) {
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case DEFINE:
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/* draw grid */
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glColor3f( 0.6, 0.5, 0.5 );
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glBegin( GL_LINES );
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for ( ii = 0 ; ii < width ; ii += 10 ) {
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for ( jj = 0 ; jj < height ; jj += 10 ) {
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glVertex2i( 0, jj );
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glVertex2i( width, jj );
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glVertex2i( ii, height );
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glVertex2i( ii, 0 );
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}
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}
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glEnd();
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glColor3f( 1.0, 1.0, 0.0 );
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for ( i = 0 ; i <= contour_cnt ; i++ ) {
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point_cnt = contours[i].point_cnt;
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glBegin( GL_LINES );
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switch ( point_cnt ) {
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case 0:
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break;
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case 1:
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glVertex2fv( contours[i].p[0] );
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glVertex2fv( contours[i].p[0] );
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break;
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case 2:
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glVertex2fv( contours[i].p[0] );
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glVertex2fv( contours[i].p[1] );
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break;
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default:
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--point_cnt;
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for ( j = 0 ; j < point_cnt ; j++ ) {
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glVertex2fv( contours[i].p[j] );
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glVertex2fv( contours[i].p[j+1] );
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}
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if ( contours[i].p[j+1][0] == -1 ) {
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glVertex2fv( contours[i].p[0] );
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glVertex2fv( contours[i].p[j] );
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}
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break;
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}
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glEnd();
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}
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glFinish();
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break;
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case TESSELATED:
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/* draw triangles */
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glColor3f( 0.7, 0.7, 0.0 );
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glCallList( list_start );
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glLineWidth( 2.0 );
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glCallList( list_start + 1 );
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glLineWidth( 1.0 );
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glFlush();
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break;
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}
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glColor3f( 1.0, 1.0, 0.0 );
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}
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static void clear( void )
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{
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contour_cnt = 0;
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contours[0].point_cnt = 0;
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triangle_cnt = 0;
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glutMouseFunc( mouse_clicked );
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mode = DEFINE;
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glDeleteLists( list_start, 2 );
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list_start = 0;
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}
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static void quit( void )
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{
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exit( 0 );
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}
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static void menu_selected( int entry )
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{
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switch ( entry ) {
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case CLEAR:
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clear();
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break;
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case TESSELATE:
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tesse();
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break;
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case QUIT:
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quit();
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break;
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}
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glutPostRedisplay();
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}
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static void key_pressed( unsigned char key, int x, int y )
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{
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(void) x;
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(void) y;
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switch ( key ) {
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case 'c':
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case 'C':
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clear();
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break;
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case 't':
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case 'T':
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tesse();
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break;
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case 27:
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case 'q':
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case 'Q':
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quit();
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break;
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}
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glutPostRedisplay();
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}
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static void myinit( void )
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{
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/* clear background to gray */
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glClearColor( 0.4, 0.4, 0.4, 0.0 );
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glShadeModel( GL_FLAT );
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glPolygonMode( GL_FRONT, GL_FILL );
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menu = glutCreateMenu( menu_selected );
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glutAddMenuEntry( "clear", CLEAR );
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glutAddMenuEntry( "tesselate", TESSELATE );
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glutAddMenuEntry( "quit", QUIT );
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glutAttachMenu( GLUT_RIGHT_BUTTON );
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glutMouseFunc( mouse_clicked );
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glutKeyboardFunc( key_pressed );
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contour_cnt = 0;
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mode = DEFINE;
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}
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static void reshape( GLsizei w, GLsizei h )
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{
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glViewport( 0, 0, w, h );
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glMatrixMode( GL_PROJECTION );
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glLoadIdentity();
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glOrtho( 0.0, (GLdouble)w, 0.0, (GLdouble)h, -1.0, 1.0 );
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glMatrixMode( GL_MODELVIEW );
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glLoadIdentity();
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set_screen_wh( w, h );
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}
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#endif
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static void usage( void )
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{
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printf( "Use left mouse button to place vertices.\n" );
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printf( "Press middle mouse button when done.\n" );
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printf( "Select tesselate from the pop-up menu.\n" );
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}
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int main( int argc, char **argv )
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{
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const char *version = (const char *) gluGetString( GLU_VERSION );
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printf( "GLU version string: %s\n", version );
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if ( strstr( version, "1.0" ) || strstr( version, "1.1" ) ) {
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fprintf( stderr, "Sorry, this demo reqiures GLU 1.2 or later.\n" );
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exit( 1 );
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}
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usage();
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glutInit( &argc, argv );
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glutInitDisplayMode( GLUT_SINGLE | GLUT_RGB );
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glutInitWindowPosition(0, 0);
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glutInitWindowSize( 400, 400 );
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glutCreateWindow( argv[0] );
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/* GH: Bit of a hack...
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*/
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#ifdef GLU_VERSION_1_2
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myinit();
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glutDisplayFunc( display );
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glutReshapeFunc( reshape );
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glutMainLoop();
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#endif
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return 0;
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}
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