请你用c语言和OpenGL库编写一程序,实现多边形的逐边剪裁算法的示例代码
时间: 2024-06-09 20:11:16 浏览: 15
好的,以下是一个基于C语言和OpenGL库的多边形逐边剪裁算法的示例代码:
```c
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
#define MAX_POLY 10
#define MAX_VERT 20
typedef struct {
GLfloat x,y;
} point;
typedef struct {
point vert[MAX_VERT];
int num_vert;
} polygon;
typedef struct {
point p1,p2;
} edge;
polygon poly[MAX_POLY];
int num_poly = 0;
edge clip_win[4] = {{{-0.5,-0.5},{-0.5,0.5}}},
{{-0.5,0.5},{0.5,0.5}}},
{{0.5,0.5},{0.5,-0.5}}},
{{0.5,-0.5},{-0.5,-0.5}}};
void draw_clip_win() {
glBegin(GL_LINE_LOOP);
glVertex2f(-0.5,-0.5);
glVertex2f(-0.5,0.5);
glVertex2f(0.5,0.5);
glVertex2f(0.5,-0.5);
glEnd();
}
void draw_poly(int i) {
int j;
glBegin(GL_LINE_LOOP);
for(j=0;j<poly[i].num_vert;j++)
glVertex2f(poly[i].vert[j].x,poly[i].vert[j].y);
glEnd();
}
int inside(point p, edge e) {
GLfloat x1=e.p1.x, y1=e.p1.y, x2=e.p2.x, y2=e.p2.y;
GLfloat t = (p.x-x1)*(y2-y1)-(p.y-y1)*(x2-x1);
return (t >= 0);
}
int intersect(edge e, edge clip, point *p) {
GLfloat x1=e.p1.x, y1=e.p1.y, x2=e.p2.x, y2=e.p2.y;
GLfloat x3=clip.p1.x, y3=clip.p1.y, x4=clip.p2.x, y4=clip.p2.y;
GLfloat denom = (x1-x2)*(y3-y4)-(y1-y2)*(x3-x4);
if(denom == 0) return 0;
GLfloat t = ((x1-x3)*(y3-y4)-(y1-y3)*(x3-x4))/denom;
GLfloat x = x1+t*(x2-x1);
GLfloat y = y1+t*(y2-y1);
if(t>=0 && t<=1 && (x>=-0.5 && x<=0.5) && (y>=-0.5 && y<=0.5)) {
p->x = x; p->y = y;
return 1;
}
return 0;
}
void sutherland_hodgman(int i) {
int j,k;
polygon out_poly;
point S, P;
for(j=0;j<poly[i].num_vert;j++) {
if(j == 0) S = poly[i].vert[poly[i].num_vert-1];
else S = poly[i].vert[j-1];
P = poly[i].vert[j];
if(inside(P,clip_win[0])) {
if(!inside(S,clip_win[0]))
intersect((edge){S,P},clip_win[0],&out_poly.vert[out_poly.num_vert++]);
out_poly.vert[out_poly.num_vert++] = P;
}
else if(inside(S,clip_win[0]))
intersect((edge){S,P},clip_win[0],&out_poly.vert[out_poly.num_vert++]);
}
poly[i] = out_poly;
out_poly.num_vert = 0;
for(k=1;k<4;k++) {
for(j=0;j<poly[i].num_vert;j++) {
if(j == 0) S = poly[i].vert[poly[i].num_vert-1];
else S = poly[i].vert[j-1];
P = poly[i].vert[j];
if(inside(P,clip_win[k])) {
if(!inside(S,clip_win[k]))
intersect((edge){S,P},clip_win[k],&out_poly.vert[out_poly.num_vert++]);
out_poly.vert[out_poly.num_vert++] = P;
}
else if(inside(S,clip_win[k]))
intersect((edge){S,P},clip_win[k],&out_poly.vert[out_poly.num_vert++]);
}
poly[i] = out_poly;
out_poly.num_vert = 0;
}
}
void display() {
int i;
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0,1.0,1.0);
draw_clip_win();
glColor3f(0.0,0.0,1.0);
for(i=0;i<num_poly;i++) {
draw_poly(i);
sutherland_hodgman(i);
}
glColor3f(1.0,0.0,0.0);
for(i=0;i<num_poly;i++) draw_poly(i);
glFlush();
}
void init() {
glClearColor(0.0,0.0,0.0,0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(-0.5,0.5,-0.5,0.5);
glMatrixMode(GL_MODELVIEW);
}
void keyboard(unsigned char key, int x, int y) {
if(key == 'q' || key == 'Q') exit(0);
}
void mouse(int button, int state, int x, int y) {
static int vert = 0;
static int poly_num = 0;
GLfloat xf, yf;
if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {
xf = ((GLfloat)x/glutGet(GLUT_WINDOW_WIDTH))*2.0-1.0;
yf = ((GLfloat)(glutGet(GLUT_WINDOW_HEIGHT)-y)/glutGet(GLUT_WINDOW_HEIGHT))*2.0-1.0;
poly[poly_num].vert[vert].x = xf;
poly[poly_num].vert[vert].y = yf;
poly[poly_num].num_vert++;
vert++;
}
else if(button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN) {
num_poly++;
poly_num++;
vert = 0;
}
glutPostRedisplay();
}
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(500,500);
glutInitWindowPosition(100,100);
glutCreateWindow("Polygon Clipping");
init();
glutDisplayFunc(display);
glutKeyboardFunc(keyboard);
glutMouseFunc(mouse);
glutMainLoop();
return 0;
}
```
该程序实现了一个简单的多边形逐边剪裁算法,并提供了鼠标操作来绘制多边形。你可以尝试在程序中添加更多的多边形进行测试。
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