计算机图形学Cohen_Sutherland算法裁剪线段

/**

*时间：2011年12月20日

*作者：鲍志强

*功能：直线的裁剪

*指导老师：杜吉祥

**/

#include<GL/glut.h>

#include<math.h>

#include<iostream>

using namespace std;

//定义窗口结构体

typedef struct Window

{

float Xwl;

float Xwr;

float Ywt;

float Ywb;

} *win;

//画窗体

void drawWindow(win pw)

{

glBegin(GL_LINE_LOOP);

glColor3f(1.0,0.0,0.0);

glVertex2f(pw->Xwl,pw->Ywt);

glVertex2f(pw->Xwl,pw->Ywb);

glVertex2f(pw->Xwr,pw->Ywb);

glVertex2f(pw->Xwr,pw->Ywt);

glEnd();

glFlush();

}

//画线

void drawLine(float *p,float *c)

{

glLineWidth(3);   //设置直线的宽度

glBegin(GL_LINES);

glColor3f(c[0],c[1],c[2]);

glVertex2f(p[0],p[1]);

glVertex2f(p[2],p[3]);

glEnd();

glFlush();

}

void Cohen_Sutherland(float *Points,win pw)

{

int code1[]={0,0,0,0},

code2[]={0,0,0,0};

float cutColor[]={0.0,0.0,0.0};

//求出 code1

if(Points[0]<pw->Xwl)

code1[3]=1;

else if(Points[0]>pw->Xwr)

code1[2]=1;

if(Points[1]<pw->Ywb)

code1[1]=1;

else if(Points[1]>pw->Ywt)

code1[0]=1;

//求出 code2

if(Points[2]<pw->Xwl)

code2[3]=1;

else if(Points[2]>pw->Xwr)

code2[2]=1;

if(Points[3]<pw->Ywb)

code2[1]=1;

else if(Points[3]>pw->Ywt)

code2[0]=1;

//判断是否能够 简取

if(code1[0]|code2[0] &&

code1[1]|code2[1] &&

code1[2]|code2[2] &&

code1[3]|code2[3])

{

cout<<"简取线段！"<<endl;

drawLine(Points,cutColor);

return;

}

//判断是否能够 简弃

if(code1[0]&code2[0] ||

code1[1]&code2[1] ||

code1[2]&code2[2] ||

code1[3]&code2[3])

{

cout<<"简弃线段！"<<endl;

return;

}

//不能 简取 简弃，求出所有交点

float k=(Points[3]-Points[1])/(Points[2]-Points[0]);

float x=0,y=0;

float temp[8]={0};

float node[4]={0};

x=pw->Xwl;

y=(Points[1]+((Points[3]-Points[1])/(Points[2]-Points[0]))*(x-Points[0]));

temp[0]=x;

temp[1]=y;

x=pw->Xwr;

y=(Points[1]+((Points[3]-Points[1])/(Points[2]-Points[0]))*(x-Points[0]));

temp[2]=x;

temp[3]=y;

y=pw->Ywb;

x=(Points[0]+(y-Points[1])/((Points[3]-Points[1])/(Points[2]-Points[0])));

temp[4]=x;

temp[5]=y;

y=pw->Ywt;

x=(Points[0]+(y-Points[1])/((Points[3]-Points[1])/(Points[2]-Points[0])));

temp[6]=x;

temp[7]=y;

//取出实交点

for(int i=0;i<4;i++)

{

if(temp[i*2]>=pw->Xwl &&

temp[i*2]<=pw->Xwr &&

temp[i*2+1]>=pw->Ywb &&

temp[i*2+1]<=pw->Ywt)

{

cout<<temp[i*2]<<"  "<<temp[i*2+1]<<endl;

if(temp[i*2]<Points[0])

{

if(node[0]==0)

{

node[0]=Points[0];

node[1]=Points[1];

}

else

{

node[2]=Points[0];

node[3]=Points[1];

}

}

else if(temp[i*2]>Points[2])

{

if(node[0]==0)

{

node[0]=Points[2];

node[1]=Points[3];

}

else

{

node[2]=Points[2];

node[3]=Points[3];

}

}

else

{

if(node[0]==0)

{

node[0]=temp[i*2];

node[1]=temp[i*2+1];

}

else

{

node[2]=temp[i*2];

node[3]=temp[i*2+1];

}

}

}

}

drawLine(node,cutColor);

}

//显示回调函数

void OnDisplay()

{

//消除颜色缓冲区

glClear(GL_COLOR_BUFFER_BIT);

//定义四条直线

float Points1[]={50,200,300,500};

float Points2[]={150,200,400,400};

float Points3[]={250,200,600,400};

float Points4[]={50,450,200,500};

float color[]={1.0,0,0};

//定义裁剪窗口

//数组格式为：minX maxX minY maxY

win pw=(win)malloc(sizeof(Window)); //声明一个窗口的全局变量

pw->Xwl=100;

pw->Xwr=550;

pw->Ywb=100;

pw->Ywt=450;

drawLine(Points1,color);

drawLine(Points2,color);

drawLine(Points3,color);

drawLine(Points4,color);

drawWindow(pw);

//裁剪直线

Cohen_Sutherland(Points1,pw);

Cohen_Sutherland(Points2,pw);

Cohen_Sutherland(Points3,pw);

Cohen_Sutherland(Points4,pw);

}

void OnReshape(int w,int h)

{

glClearColor(1.0f,1.0f,1.0f,0.0f);      //设置背景颜色

gluOrtho2D(0,w,0,h); //将当前绘图区域设置为二维正交投影的

}

int main(int argc, char *argv[])

{

glutInit(&argc,argv);

glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);

glutInitWindowSize(700,600);

glutInitWindowPosition(200,100);

glutCreateWindow("My OpenGL");

glutDisplayFunc(&OnDisplay);

glutReshapeFunc(&OnReshape);

glutMainLoop();

return 0;

}