http://blog.csdn.net/nanhaizhixin/article/details/6531896
【Sutherlang-Hodgman 多边形裁剪算法】
#include
#include
#include
#includetypedef 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.xwMax.x) return (false);
break;
case Bottom:
if(p.ywMax.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);
else
return true;
}wcPt2D Intersect(wcPt2D p1,wcPt2D p2,Boundary b,wcPt2D wMin,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);
}voidinit (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 
