Le source : RasterisationCercle.cpp
/* Un programme OpenGL de rasterisation */
/* d'un cercle */
/* */
/* Auteur: Nicolas JANEY */
/* nicolas.janey@univ-fcomte.fr */
/* Novembre 2009 */
#include <stdlib.h>
#include <stdio.h>
#include <GL/glut.h>
#include <GL/gl.h>
#include <GL/glu.h>
static int scn = 0;
static int r = 50;
/* Scene dessinee */
void pixelsSymetriques(int x,int y) {
glVertex2f(x,y);
glVertex2f(-x,y);
glVertex2f(x,-y);
glVertex2f(-x,-y);
glVertex2f(y,x);
glVertex2f(-y,x);
glVertex2f(y,-x);
glVertex2f(-y,-x);
}
void cercle(int r) {
int x,y,d;
x = 0;
y = r;
d = 1 - r;
glBegin(GL_POINTS);
pixelsSymetriques(x,y);
while ( y > x ) {
if ( d < 0 )
d += 2 * x + 3;
else {
d += 2 * (x - y) + 5;
y--; }
x++;
pixelsSymetriques(x,y); }
glEnd();
}
void scene1(void) {
glPushMatrix();
glColor3f(0.0F,0.0F,0.0F);
cercle(r);
glPopMatrix();
}
void disque(int r) {
int *tx =(int *) calloc(r+1,sizeof(int));
int x,y,d;
x = 0;
y = r;
d = 1 - r;
tx[y] = x;
tx[x] = y;
while ( y > x ) {
if ( d < 0 )
d += 2 * x + 3;
else {
d += 2 * (x - y) + 5;
y--; }
x++;
tx[y] = x;
tx[x] = y; }
glBegin(GL_LINES);
glVertex2i(tx[0],0);
glVertex2i(-tx[0],0);
for ( int i = 1 ; i <= r ; i++ ) {
glVertex2i(tx[i],i);
glVertex2i(-tx[i],i);
glVertex2i(tx[i],-i);
glVertex2i(-tx[i],-i); }
glEnd();
free(tx);
}
void scene2(void) {
glPushMatrix();
glColor3f(0.0F,0.0F,0.0F);
disque(r);
glPopMatrix();
}
/* Fonction executee lors d'un rafraichissement */
/* de la fenetre de dessin */
void display(void) {
glClearColor(1.0F,1.0F,1.0F,1.0F);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
if ( scn == 0 )
scene1();
else
scene2();
glPopMatrix();
glFlush();
glutSwapBuffers();
}
/* Fonction executee lors d'un changement */
/* de la taille de la fenetre OpenGL */
void reshape(int x,int y) {
glViewport(0,0,x,y);
glMatrixMode(GL_PROJECTION) ;
glLoadIdentity() ;
glOrtho(-x/2,-x/2+x,-y/2,-y/2+y,-300.0,300.0) ;
glMatrixMode(GL_MODELVIEW) ;
glLoadIdentity() ;
}
/* Fonction executee lors de l'appui */
/* d'une touche alphanumerique du clavier */
void keyboard(unsigned char key,int x,int y) {
switch (key) {
case 43 :
r++;
glutPostRedisplay();
break;
case 45 :
r--;
if ( r == 0 )
r = 1;
else
glutPostRedisplay();
break;
case 0x0D :
scn = !scn;
glutPostRedisplay();
break;
case 0x1B :
exit(0);
break; }
}
/* Fonction principale */
int main(int argc,char **argv) {
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_RGBA|GLUT_DEPTH|GLUT_DOUBLE);
glutInitWindowSize(240,240);
glutInitWindowPosition(50,50);
glutCreateWindow("Rasterisation d'un cercle");
glutKeyboardFunc(keyboard);
glutReshapeFunc(reshape);
glutDisplayFunc(display);
glutMainLoop();
return(0);
}
RETOUR