/* gasket.c   */

/* E. Angel, Interactive Computer Graphics */
/* A Top-Down Approach with OpenGL, Third Edition */
/* Addison-Wesley Longman, 2003 */
/* Two-Dimensional Sierpinski Gasket          *//* Generated Using Randomly Selected Vertices *//* And Bisection                              */#include <GL/glut.h>void myinit(void){ /* attributes */      glClearColor(1.0, 1.0, 1.0, 1.0); /* white background */      glColor3f(1.0, 0.0, 0.0); /* draw in red *//* set up viewing *//* 500 x 500 window with origin lower left */      glMatrixMode(GL_PROJECTION);      glLoadIdentity();      gluOrtho2D(0.0, 500.0, 0.0, 500.0);      glMatrixMode(GL_MODELVIEW);}void display( void ){/* define a point data type */    typedef GLfloat point2[2];         point2 vertices[3]={{0.0,0.0},{250.0,500.0},{500.0,0.0}}; /* A triangle */    int i, j, k;    int rand();       /* standard random number generator */    point2 p ={75.0,50.0};  /* An arbitrary initial point inside traingle */    glClear(GL_COLOR_BUFFER_BIT);  /*clear the window *//* compute and plots 5000 new points */    for( k=0; k<5000; k++)    {         j=rand()%3; /* pick a vertex at random */     /* Compute point halfway between selected vertex and old point */         p[0] = (p[0]+vertices[j][0])/2.0;          p[1] = (p[1]+vertices[j][1])/2.0;        /* plot new point */          glBegin(GL_POINTS);               glVertex2fv(p);           glEnd();        }     glFlush(); /* clear buffers */ }void main(int argc, char** argv){/* Standard GLUT initialization */    glutInit(&argc,argv);    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); /* default, not needed */    glutInitWindowSize(500,500); /* 500 x 500 pixel window */    glutInitWindowPosition(0,0); /* place window top left on display */    glutCreateWindow("Sierpinski Gasket"); /* window title */    glutDisplayFunc(display); /* display callback invoked when window opened */    myinit(); /* set attributes */    glutMainLoop(); /* enter event loop */}