计算机图形学——编码裁剪

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要求：利用编码裁剪（Cohen-Sutherland）法裁剪《计算机图形学基础》（第二版）（p183 图6-40）所示线段。
#include<GL/glut.h>  #include<stdio.h>  #include<stdlib.h>    #define LEFT_EDGE 1  #define RIGHT_EDGE 2  #define BOTTOM_EDGE 4  #define TOP_EDGE 8    void LineGL(int x0,int y0,int x1,int y1)  {      glBegin(GL_LINES);      glColor3f(1.0f,0.0f,0.0f);glVertex2f(x0,y0);          glColor3f(0.0f,1.0f,0.0f);glVertex2f(x1,y1);           glEnd();                                                }                                                            struct Rectangle  {      float xmin,xmax,ymin,ymax;  };    Rectangle rect;  int x0,y0,x1,y1;    int CompCode(int x,int y,Rectangle rect)  {      int code=0x00;        if(y<rect.ymin)          code=code|4;      if(y>rect.ymax)          code=code|8;      if(x>rect.xmax)          code=code|2;      if(x<rect.xmin)          code=code|1;return code;}    int cohensutherlandlineclip(Rectangle rect,int &x0,int &y0,int &x1,int &y1)  {      int accept,done;      float x,y;      accept=0;      done=0;            int total=0,flag=0;           int code0,code1,codeout;      code0=CompCode(x0,y0,rect);      printf("code0=%d\n",code0);      code1=CompCode(x1,y1,rect);      printf("code1=%d\n",code1);      do{          if(!(code0|code1))               {              accept=1;              done=1;          }          else if(code0 & code1)          {              done=1;flag=1;          }                     else          {              if(code0!=0)                  codeout=code0;              else                  codeout=code1;                if(codeout&LEFT_EDGE)              {                  y=y0+(y1-y0)*(rect.xmin-x0)/(x1-x0);                  x=(float)rect.xmin;              }              else if(codeout&RIGHT_EDGE)              {                  y=y0+(y1-y0)*(rect.xmax-x0)/(x1-x0);                  x=(float)rect.xmax;              }              else if(codeout&BOTTOM_EDGE)              {                  x=x0+(x1-x0)*(rect.ymin-y0)/(y1-y0);                  y=(float)rect.ymin;              }              else if(codeout&TOP_EDGE)              {                  x=x0+(x1-x0)*(rect.ymax-y0)/(y1-y0);                  y=(float)rect.ymax;              }              if(codeout==code0)              {                  x0=x;   y0=y;                  code0=CompCode(x0,y0,rect);              }              else              {                  x1=x;   y1=y;                  code1=CompCode(x1,y1,rect);              }              total++;              if(total>2)                          {                  done=1;flag=1;              }          }             }while(!done);            if(accept)                  LineGL(x0,y0,x1,y1);      else      {          x0=0;y=0;x1=0;y1=0;          LineGL(x0,y0,x1,y1);      }                return accept;  }    void myDisplay()  {      glClear(GL_COLOR_BUFFER_BIT);      glColor3f(1.0f,1.0f,1.0f);      glRectf(rect.xmin,rect.ymin,rect.xmax,rect.ymax);      LineGL(x0,y0,x1,y1);      glFlush();  }    void Init()  {      glClearColor(0.0,0.0,0.0,0.0);      glShadeModel(GL_FLAT);        rect.xmin=200;  //设置坐标系  原坐标应为（0,0）（2,0）（0,2）（2,2）改为（200,200）（400,200）（200,400）（400,400）    rect.xmax=400;      rect.ymin=200;      rect.ymax=400;        x0=100,y0=0,x1=500,y1=500;    //为方便看，将原坐标（-1，-2）改为（100,0），（3，3）改为（500,500）}    void Reshape(int w,int h)  {      glViewport(0,0,(GLsizei) w,(GLsizei) h);      glMatrixMode(GL_PROJECTION);      glLoadIdentity();       gluOrtho2D(0.0,(GLdouble) w,0.0,(GLdouble) h);  //定义窗口大小}   int main(int argc,char *argv[])  {      glutInit(&argc,argv);      glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);      glutInitWindowPosition(100,100);      glutInitWindowSize(640,480);      glutCreateWindow("Cohen-Sutherland");       Init();      glutDisplayFunc(myDisplay);      glutReshapeFunc(Reshape);      glutMainLoop();            return 0;  }
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