?? liangbarsk.cpp
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#include<GL/glut.h>
#include<math.h>
const int nVerts=6;//多邊形頂點數(shù)
const int maxVerts=10;//裁剪后最大頂點個數(shù)
int countVerts=0;//頂點計數(shù)
bool flag=true;
class wcPt2D
{
private:
GLfloat x,y;
public:
wcPt2D()
{
x=y=0.0;
}
void setCoords(GLfloat xCoord,GLfloat yCoord)
{
x=xCoord;
y=yCoord;
}
GLfloat getx()const
{
return x;
}
GLfloat gety()const
{
return y;
}
};
wcPt2D Pverts[nVerts];//原多邊形
wcPt2D CPverts[maxVerts];//裁剪后多邊形
wcPt2D winMin,winMax;//定義裁剪窗口
GLint clipTest(GLfloat p,GLfloat q,GLfloat &u1,GLfloat &u2)
{
GLfloat r;
GLint returnValue=true;
if(p<0.0)
{
r=q/p;
if(r>u2)
returnValue=false;
else
if(r>u1)
u1=r;
}
else
if(p>0.0)
{
r=q/p;
if(r<u1)
returnValue=false;
else if(r<u2)
u2=r;
}
else
if(q<0.0)
returnValue=false;
return (returnValue);
}
void isAddVerts(wcPt2D p1,wcPt2D p2)//逆時針添加可能的裁剪窗口頂點
{
if(p1.getx()==winMax.getx())//p1在右邊界
{
if(p1.gety()!=winMax.gety())
{
if(p2.getx()!=winMax.getx())
{
CPverts[countVerts].setCoords(winMax.getx(),winMax.gety());
countVerts++;
if(p2.gety()!=winMax.gety())
{
CPverts[countVerts].setCoords(winMin.getx(),winMax.gety());
countVerts++;
if(p2.getx()!=winMin.getx())
{
CPverts[countVerts].setCoords(winMin.getx(),winMin.gety());
countVerts++;
}
}
}
}
else
{
if(p2.gety()!=winMax.gety())
{
CPverts[countVerts].setCoords(winMin.getx(),winMax.gety());
countVerts++;
if(p2.getx()!=winMin.getx())
{
CPverts[countVerts].setCoords(winMin.getx(),winMin.gety());
countVerts++;
}
}
}
}
else if(p1.gety()==winMax.gety())//p1在上邊界
{
if(p1.getx()!=winMin.getx())
{
if(p2.gety()!=winMax.gety())
{
CPverts[countVerts].setCoords(winMin.getx(),winMax.gety());
countVerts++;
if(p2.getx()!=winMin.getx())
{
CPverts[countVerts].setCoords(winMin.getx(),winMin.gety());
countVerts++;
if(p2.gety()!=winMin.gety())
{
CPverts[countVerts].setCoords(winMax.getx(),winMin.gety());
countVerts++;
}
}
}
}
else
{
if(p2.getx()!=winMin.getx())
{
CPverts[countVerts].setCoords(winMin.getx(),winMin.gety());
countVerts++;
if(p2.gety()!=winMin.gety())
{
CPverts[countVerts].setCoords(winMax.getx(),winMin.gety());
countVerts++;
}
}
}
}
else if(p1.getx()==winMin.getx())//p1在左邊界
{
if(p1.gety()!=winMin.gety())
{
if(p2.getx()!=winMin.getx())
{
CPverts[countVerts].setCoords(winMin.getx(),winMin.gety());
countVerts++;
if(p2.gety()!=winMin.gety())
{
CPverts[countVerts].setCoords(winMax.getx(),winMin.gety());
countVerts++;
if(p2.getx()!=winMax.getx())
{
CPverts[countVerts].setCoords(winMax.getx(),winMax.gety());
countVerts++;
}
}
}
}
else
{
if(p2.gety()!=winMin.gety())
{
CPverts[countVerts].setCoords(winMax.getx(),winMin.gety());
countVerts++;
if(p2.getx()!=winMax.getx())
{
CPverts[countVerts].setCoords(winMax.getx(),winMax.gety());
countVerts++;
}
}
}
}
else if(p1.gety()==winMin.gety())//p1在下邊界
{
if(p1.getx()!=winMax.getx())
{
if(p2.gety()!=winMin.gety())
{
CPverts[countVerts].setCoords(winMax.getx(),winMin.gety());
countVerts++;
if(p2.getx()!=winMax.getx())
{
CPverts[countVerts].setCoords(winMax.getx(),winMax.gety());
countVerts++;
if(p2.gety()!=winMax.gety())
{
CPverts[countVerts].setCoords(winMin.getx(),winMax.gety());
countVerts++;
}
}
}
}
else
{
if(p2.getx()!=winMax.getx())
{
CPverts[countVerts].setCoords(winMax.getx(),winMax.gety());
countVerts++;
if(p2.gety()!=winMax.gety())
{
CPverts[countVerts].setCoords(winMin.getx(),winMax.gety());
countVerts++;
}
}
}
}
}
bool lineClipLiangBarsk(wcPt2D p1,wcPt2D p2)
{
GLfloat u1=0.0,u2=1.0,dx=p2.getx()-p1.getx(),dy;
if(clipTest(-dx,p1.getx()-winMin.getx(),u1,u2))
if(clipTest(dx,winMax.getx()-p1.getx(),u1,u2))
{
dy=p2.gety()-p1.gety();
if(clipTest(-dy,p1.gety()-winMin.gety(),u1,u2))
if(clipTest(dy,winMax.gety()-p1.gety(),u1,u2))
{
if(u1==0.0)
{
CPverts[countVerts].setCoords(p1.getx()+u2*dx,p1.gety()+u2*dy);
countVerts++;
}
else if(u1>0.0&&u2<=1.0)
{
wcPt2D tmp;
tmp.setCoords(p1.getx()+u1*dx,p1.gety()+u1*dy);
if(!flag)
{
isAddVerts(CPverts[countVerts-1],tmp);
flag=true;
}
CPverts[countVerts].setCoords(tmp.getx(),tmp.gety());
countVerts++;
CPverts[countVerts].setCoords(p1.getx()+u2*dx,p1.gety()+u2*dy);
countVerts++;
}
return true;
}
}
return false;
}
void init()
{
glClearColor(1.0,1.0,1.0,0.0);
glMatrixMode(GL_PROJECTION);
gluOrtho2D(0.0,200.0,0.0,150.0);
}
void initPolygon()
{
Pverts[0].setCoords(50.0,50.0);
Pverts[1].setCoords(120.0,60.0);
Pverts[2].setCoords(150.0,80.0);
Pverts[3].setCoords(110.0,130.0);
Pverts[4].setCoords(70.0,110.0);
Pverts[5].setCoords(30.0,75.0);
}
void initClipWindow()
{
winMin.setCoords(35.0,55.0);
winMax.setCoords(110.0,90.0);
}
void showClipWindow()
{
glBegin(GL_LINE_LOOP);
glVertex2f(winMin.getx(),winMin.gety());
glVertex2f(winMax.getx(),winMin.gety());
glVertex2f(winMax.getx(),winMax.gety());
glVertex2f(winMin.getx(),winMax.gety());
glEnd();
}
void showPolygon(wcPt2D *verts,int n)
{
glBegin(GL_POLYGON);
for(int i=0;i<n;i++)
glVertex2f(verts[i].getx(),verts[i].gety());
glEnd();
}
void clip()
{
for(int i=0;i<nVerts;i++)
{
if(!lineClipLiangBarsk(Pverts[i],Pverts[(i+1)%nVerts]))
flag=false;
}
}
void displayFcn()
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.0,0.0,1.0);
initPolygon();
initClipWindow();
showPolygon(Pverts,nVerts);//原多邊形顯示
glColor3f(0.0,0.0,0.0);
showClipWindow();//裁剪窗口顯示
glColor3f(1.0,0.0,0.0);
clip();
showPolygon(CPverts,countVerts);
glFlush();
}
int main(int argc,char **argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowPosition(50,100);
glutInitWindowSize(400,300);
glutCreateWindow("Liang-Barsk Programme");
init();
glutDisplayFunc(displayFcn);
glutMainLoop();
return 0;
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