/************** Snow.cpp **************/
/*       Copyright By Nameless        */
/*         All Right Reserved         */
/*                NUDT                */
/*            Oct,27,2007             */
/**************************************/

#include <GL/glut.h>
#include <math.h>

#define DEEP 4
#define PI 3.1415926
#define RADIUS 40
#define OX 250
#define OY 175

void init()
{
 glClearColor(0.0, 0.0, 0.0, 0.0);
 glMatrixMode(GL_PROJECTION);
 gluOrtho2D(0.0,500.0,0.0,350.0);
}

void DrawSnow(GLint deep,GLint r,GLint theata,GLint x,GLint y)
{
 if (deep>=DEEP)
  return;
 int xi=r*cos(theata*PI/180);
 int yi=r*sin(theata*PI/180);
 glBegin(GL_LINES);
  glVertex2i(x,y);
  glVertex2i(x+xi,y+yi);
 glEnd();
 glBegin(GL_LINES);
  glVertex2i(OX+OX-x,OY+OY-y);
  glVertex2i(OX+OX-x-xi,OY+OY-y-yi);
 glEnd();
 DrawSnow(deep+1,r/2,theata-45,x+xi/2,y+yi/2);
 DrawSnow(deep+1,r,theata,x+xi/2,y+yi/2);
 DrawSnow(deep+1,r/2,theata+45,x+xi/2,y+yi/2);
 return;
}

void Snow()
{
 glClear(GL_COLOR_BUFFER_BIT);
 glColor3f(1.0,1.0,1.0);
 DrawSnow(0,RADIUS,90,OX,OY);
 DrawSnow(0,RADIUS,30,OX,OY);
 DrawSnow(0,RADIUS,-30,OX,OY);
 glFlush();
}

int main(int argc, char* argv[])
{
 glutInit(&argc,argv);
 glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
 glutInitWindowPosition(50,100);
 glutInitWindowSize(400,300);
 glutCreateWindow("递归雪花");
 init();
 glutDisplayFunc(Snow);
 glutMainLoop();
 return 0;
}

效果图：