编程实现Sutherlang-Hodgman多边形裁剪算法

#include<GL/glut.h>#include<iostream.h>#include<stdio.h>#include<stdlib.h>typedef struct {float x,y;}wcPt2D;typedef enum{Left,Right,Bottom,Top}Boundary;int Inside(wcPt2D p,Boundary b,wcPt2D wMin,wcPt2D wMax){switch(b){case Left:if(p.x<wMin.x) return (false) ;break;case Right:if(p.x>wMax.x) return (false);break;case Bottom:if(p.y<wMin.y) return (false);break;case Top:if(p.y>wMax.y) return (false);break;}return true;}int Cross(wcPt2D p1,wcPt2D p2,Boundary b,wcPt2D wMin,wcPt2D wMax){if(Inside(p1,b,wMin,wMax)==Inside(p2,b,wMin,wMax))return (false);elsereturn true;}wcPt2D Intersect(wcPt2D p1,wcPt2D p2,Boundary b,wcPt2DwMin,wcPt2D wMax){wcPt2D iPt;float m;if(p1.x !=p2.x) m=(p2.y-p1.y)/(p2.x-p1.x);switch(b){case Left:iPt.x=wMin.x;iPt.y=p2.y+(wMin.x-p2.x)*m;break;case Right:iPt.x=wMax.x;iPt.y=p2.y+(wMax.x-p2.x)*m;break;case Bottom:iPt.y=wMin.y;if(p1.x!=p2.x)iPt.x=p2.x + (wMin.y-p2.y)/m;else iPt.x=p2.x;break;case Top:iPt.y=wMax.y;if(p1.x!=p2.x) iPt.x=p2.x+(wMax.y-p2.y)/m;else iPt.x=p2.x;break;}return iPt;}int edgeCliper(Boundary b,wcPt2D wMin,wcPt2D wMax,wcPt2D *pIn,int cnt,wcPt2D *pOut){wcPt2D s;int i,Outcnt=0;s=pIn[0];for(i=1;i<=cnt;i++){if(!Inside(s,b,wMin,wMax)&&Inside(pIn[i],b,wMin,wMax)){pOut[Outcnt]=Intersect(s,pIn[i],b,wMin,wMax);Outcnt++;pOut[Outcnt]=pIn[i];Outcnt++;}else if(Inside(s,b,wMin,wMax)&&Inside(pIn[i],b,wMin,wMax)){pOut[Outcnt]=pIn[i];Outcnt++;}else if(Inside(s,b,wMin,wMax)&&(!Inside(pIn[i],b,wMin,wMax))){pOut[Outcnt]=Intersect(s, pIn[i], b,wMin, wMax);Outcnt++;}s=pIn[i];}return (Outcnt);}void init (void){glClearColor(1.0,1.0,1.0,0.0);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluOrtho2D(-400.0,400.0,-300.0,300.0);}void ClipPolygonSuthHodg(void){glClear(GL_COLOR_BUFFER_BIT);glMatrixMode(GL_MODELVIEW);int i,cnt,Outcnt,b;wcPt2D points[8]={{-300,-100},{-300,150},{-100,150},{-100,100},{100,100},{100,0},{0,-100},{-300,-100}}; cnt=7;wcPt2D pOut[28] ,pIn[28];wcPt2D wMin={-200,0},wMax={50,200};for(i=0; i<4*cnt; i++){pIn[i].x=0.0;pIn[i].y=0.0;pOut[i].x=0.0;pOut[i].y=0.0;} for(i=0; i<=cnt; i++) pIn[i]=points[i];glColor3f(0.0,0.0,0.0);glBegin(GL_LINE_LOOP);glVertex2f(wMin.x,wMin.y);glVertex2f(wMax.x,wMin.y);glVertex2f(wMax.x,wMax.y);glVertex2f(wMin.x,wMax.y);glEnd();glLineWidth(2.0);glBegin(GL_LINE_LOOP);for(i=0;i<cnt;i++)glVertex2f(pIn[i].x,pIn[i].y);glEnd();for(b=0;b<4;b++){Outcnt=edgeCliper(Boundary(b),wMin,wMax,pIn,cnt,pOut);for(i=0;i<Outcnt;i++)pIn[i]=pOut[i];pIn[Outcnt]=pOut[0];cnt=Outcnt;}glColor3f(1.0,0.0,0.0);glBegin(GL_LINE_LOOP); for(i=0;i<cnt;i++) glVertex2f(pOut[i].x,pOut[i].y);glEnd();glFlush();}void main(int argc,char **argv){glutInit(&argc,argv);glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);glutInitWindowPosition(50,100);glutInitWindowSize (800, 600);glutCreateWindow ("An Example OpenGL Program");init();glutDisplayFunc (ClipPolygonSuthHodg);glutMainLoop ();}