Le source : TD-CohenSutherland.cpp
/* Auteur: Nicolas JANEY */
/* nicolas.janey@univ-fcomte.fr */
/* Avril 2003 */
/* Clipping de Cohen-Sutherland */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include "ModuleCouleurs.h"
#include "ModuleMenus.h"
#include "ModuleReshape.h"
struct point {
int x ;
int y ; } ;
struct segment {
point pi ;
point pf ; } ;
struct rectangle {
point ig ;
point sd ; } ;
struct code {
int c1 ;
int c2 ;
int c3 ;
int c4 ; } ;
static int aff = 0 ;
static segment s1 = { { 2,10 },
{ 27,19 } } ;
static segment s2 = { { 5,9 },
{ 28,4 } } ;
void pixel(int x,int y,float *c) {
glColor4fv(c) ;
glBegin(GL_QUADS) ;
glVertex2f(x-1.0F,y-1.0F) ;
glVertex2f(x-1.0F,y) ;
glVertex2f(x,y) ;
glVertex2f(x,y-1.0F) ;
glEnd() ;
}
void line(point *pi,point *pf,float *c) {
int dx,dy,i,xinc,yinc,cumul,x,y ;
x = pi->x ;
y = pi->y ;
dx = pf->x - pi->x ;
dy = pf->y - pi->y ;
xinc = ( dx > 0 ) ? 1 : -1 ;
yinc = ( dy > 0 ) ? 1 : -1 ;
dx = abs(dx) ;
dy = abs(dy) ;
pixel(x,y,c) ;
if ( dx > dy ) {
cumul = dx / 2 ;
for ( i = 1 ; i <= dx ; i++ ) {
x += xinc ;
cumul += dy ;
if (cumul >= dx) {
cumul -= dx ;
y += yinc ; }
pixel(x,y,c) ; } }
else {
cumul = dy / 2 ;
for ( i = 1 ; i <= dy ; i++ ) {
y += yinc ;
cumul += dx ;
if ( cumul >= dy ) {
cumul -= dy ;
x += xinc ; }
pixel(x,y,c) ; } }
}
void traceRectangle(rectangle *r,float *c) {
point id = { r->sd.x,r->ig.y };
point sg = { r->ig.x,r->sd.y };
line(&id,&r->ig,c) ;
line(&id,&r->sd,c) ;
line(&sg,&r->ig,c) ;
line(&sg,&r->sd,c) ;
}
void getCode(point *p,rectangle *r,code *c) {
c->c1 = p->x < r->ig.x;
c->c2 = p->x > r->sd.x;
c->c3 = p->y < r->ig.y;
c->c4 = p->y > r->sd.y;
}
void affichageCode(code *c) {
printf("%d%d%d%d\n",c->c1,c->c2,c->c3,c->c4);
}
int codeNul(code *c) {
return(!(c->c1 || c->c2 || c->c3 || c->c4)) ;
}
int pas1commun(code *c1,code *c2) {
if ( c1->c1 && c2->c1 )
return(0);
if ( c1->c2 && c2->c2 )
return(0);
if ( c1->c3 && c2->c3 )
return(0);
if ( c1->c4 && c2->c4 )
return(0);
return(1) ;
}
int code0(code *c) {
return(c->c1) ;
}
int code1(code *c) {
return(c->c2) ;
}
int code2(code *c) {
return(c->c3) ;
}
int code3(code *c) {
return(c->c4) ;
}
int intersection(int ai,int bi,int af,int bf,int val) {
int res = 0 ;
if ( af-ai != 0 )
res =(int) (0.499 + bi +(double) (val-ai) / (af-ai) * (bf-bi)) ;
else
res = 32767 ;
return(res) ;
}
void clipperSegment(rectangle *r,segment *s,float *c) {
segment se = *s ;
code c1,c2 ;
point p ;
getCode(&s->pi,r,&c1) ;
getCode(&s->pf,r,&c2) ;
while ( ( !codeNul(&c1) || !codeNul(&c2) ) && ( pas1commun(&c1,&c2) ) ) {
if ( codeNul(&c1) ) {
p = s->pi ;
s->pi = s->pf ;
s->pf = p ;
c1 = c2 ; }
if ( code0(&c1) ) {
s->pi.y = intersection(s->pi.x,s->pi.y,s->pf.x,s->pf.y,r->ig.x) ;
s->pi.x = r->ig.x ; }
else
if ( code1(&c1) ) {
s->pi.y = intersection(s->pi.x,s->pi.y,s->pf.x,s->pf.y,r->sd.x) ;
s->pi.x = r->sd.x ; }
else
if ( code2(&c1) ) {
s->pi.x = intersection(s->pi.y,s->pi.x,s->pf.y,s->pf.x,r->ig.y) ;
s->pi.y = r->ig.y ; }
else
if ( code3(&c1) ) {
s->pi.x = intersection(s->pi.y,s->pi.x,s->pf.y,s->pf.x,r->sd.y) ;
s->pi.y = r->sd.y ; }
getCode(&s->pi,r,&c1) ;
getCode(&s->pf,r,&c2) ; }
if ( codeNul(&c1) && codeNul(&c2) )
line(&s->pi,&s->pf,c) ;
*s = se ;
}
void dessineQuadrillage(void) {
float i;
glColor4fv(couleurGrisMoyen()) ;
glBegin(GL_LINES);
for ( i = 0 ; i <= 30 ; i++ ) {
glVertex3d(i,0,-10.0);
glVertex3d(i,20,-10.0); }
for ( i = 0 ; i <= 20 ; i++ ) {
glVertex3d(0,i,-10.0);
glVertex3d(30,i,-10.0); }
glEnd() ;
}
void display() {
rectangle r = { 6,5,26,15 } ;
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glPushMatrix();
dessineQuadrillage();
traceRectangle(&r,couleurRouge(0.6F));
switch ( aff) {
case 1 : line(&s1.pi,
&s1.pf,
couleurBleu(0.5));
line(&s2.pi,
&s2.pf,
couleurVertFonce(0.5));
break ;
case 2 : line(&s1.pi,
&s1.pf,
couleurBleu(0.3));
line(&s2.pi,
&s2.pf,
couleurVertFonce(0.3));
clipperSegment(&r,
&s1,
couleurBleu(0.8));
clipperSegment(&r,
&s2,
couleurVertFonce(0.8));
break ;
case 3 : clipperSegment(&r,
&s1,
couleurBleu(0.8));
clipperSegment(&r,
&s2,
couleurVertFonce(0.8));
break ; }
glPopMatrix();
glFlush();
glutSwapBuffers() ;
}
void special(int key,int x,int y) {
}
void key(unsigned char key,int x,int y) {
switch ( key ) {
case 0x0D : aff = (aff+1)%4 ;
glutPostRedisplay();
break;
case 0x1B : exit(0);
break; }
}
void myinit() {
glEnable(GL_ALPHA_TEST);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);
glClearColor(0.8F,0.8F,0.8F,1.0F);
}
int main(int argc,char **argv) {
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_RGBA|GLUT_DEPTH|GLUT_DOUBLE);
glutInitWindowSize(375,252);
glutInitWindowPosition(50,50);
glutCreateWindow("Clipping Cohen-Sutherland");
myinit();
creationMenuBasique();
setParametresOrthoBasique(-0.5,20.5,-0.5,20.5,-50.0,50.0);
glutReshapeFunc(reshapeOrthoBasique);
glutSpecialFunc(special);
glutKeyboardFunc(key);
glutDisplayFunc(display);
glutMainLoop();
return(0);
}
RETOUR