橡皮筋技术的实现

 #include<gl\glut.h>int iPointNum=0;int x1=0,x2=2,y1=0,y2=0;int winWidth=400,winHeight=300;void Initial(void){ glClearColor(1.0f,1.0f,1.0f,1.0f);}void ChangeSize(int w,int h){ winWidth=w; winHeight=h; glViewport(0,0,w,h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(0.0,winWidth,0.0,winHeight);}void Display(void){ glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0f,0.0f,0.0f); if(iPointNum>=1) {  glBegin(GL_LINES);  glVertex2i(x1,y1);  glVertex2i(x2,y2);  glEnd(); } glutSwapBuffers();}void MousePlot(GLint button,GLint action,GLint xMouse,GLint yMouse){ if(button==GLUT_LEFT_BUTTON && action==GLUT_DOWN) {  if(iPointNum==0||iPointNum==2)  {   iPointNum=1;   x1=xMouse;   y1=winHeight-yMouse;  }  else  {   iPointNum=2;   x2=xMouse;   y2=winHeight-yMouse;   glutPostRedisplay();  } } if(button==GLUT_RIGHT_BUTTON&&action==GLUT_DOWN) {  iPointNum=0;  glutPostRedisplay(); }}void PassiveMouseMove(GLint xMouse,GLint yMouse){  if(iPointNum==1)  {   x2=xMouse;   y2=winHeight-yMouse;   glutPostRedisplay();   }}int main(int argc,char*argv[]){  glutInit(&argc,argv);  glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB);  glutInitWindowSize(400,300);  glutInitWindowPosition(100,100);  glutCreateWindow("橡皮筋技术");  glutDisplayFunc(Display);  glutReshapeFunc(ChangeSize);  glutMouseFunc(MousePlot);  glutPassiveMotionFunc(PassiveMouseMove);  Initial();  glutMainLoop();  return 0;}