gistfile1.cpp

/* recursive subdivision of triangle to form Sierpinski gasket */
/* number of recursive steps given on command line */
#include<time.h>
#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

/* initial triangle */
typedef GLfloat point3[3];
point3 v[]={{-1.0, -0.58,0.0}, {1.0, -0.58,0.0}, {0.0, 1.15,0.0},{0.0,0.0,-1.73}};

int n = 1; /* number of recursive steps */
int dg = 0 ;
void triangle( point3 a, point3 b, point3 c, point3 d)
{
    /* draw one triangle */
    glColor3f(1.0, 0.0, 0.0);
    glVertex3fv(a);
    glVertex3fv(b);
    glVertex3fv(c);
    glColor3f(0.0, 1.0, 0.0);
    glVertex3fv(a);
    glVertex3fv(c);
    glVertex3fv(d);
    glColor3f(0.0, 0.0, 1.0);
    glVertex3fv(a);
    glVertex3fv(d);
    glVertex3fv(b);
    glColor3f(0.0, 0.0, 1.0);
    glVertex3fv(b);
    glVertex3fv(d);
    glVertex3fv(c);
}

void divide_triangle(point3 a, point3 b, point3 c, point3 d , int m)
{
    /* triangle subdivision using vertex numbers */
    point3 v0, v1, v2, v3, v4, v5;
    int j;
    if(m > 0)
    {
        for(j=0; j<3; j++) v0[j]=(a[j]+b[j])/2;
        for(j=0; j<3; j++) v1[j]=(a[j]+c[j])/2;
        for(j=0; j<3; j++) v4[j]=(d[j]+a[j])/2;
        for(j=0; j<3; j++) v2[j]=(b[j]+c[j])/2;
        for(j=0; j<3; j++) v3[j]=(d[j]+c[j])/2;
        for(j=0; j<3; j++) v5[j]=(d[j]+b[j])/2;
        
        divide_triangle(a, v0, v1, v4, m-1);
        divide_triangle(v0, v1, v2, v5, m-1);
        divide_triangle(v1, v2, c, v3, m-1);
        divide_triangle(v4, v5, v3, d, m-1);
    }
    else triangle(a,b,c,d); /* draw triangle at end of recursion */
}


void display()
{
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW);	//#do Rotate, Translate, Scale.
    glLoadIdentity();
    glRotatef(dg,0,1,0);
    glBegin(GL_TRIANGLES);
    divide_triangle(v[0], v[1], v[2], v[3], n);
    glEnd();
    glFlush();
}

void myinit()
{
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(-2.0, 2.0, -2.0, 2.0);
    glMatrixMode(GL_MODELVIEW);
    glClearColor (1.0, 1.0, 1.0, 1.0);
    glColor3f(0.0,0.0,0.0);
    glEnable(GL_DEPTH_TEST);
    
}
void myReshape(int w, int h)
{
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    if (w <= h)
        glOrtho(-2.0, 2.0, -2.0 * (GLfloat) h / (GLfloat) w,
                2.0 * (GLfloat) h / (GLfloat) w, -10.0, 10.0);
    else
        glOrtho(-2.0 * (GLfloat) w / (GLfloat) h,
                2.0 * (GLfloat) w / (GLfloat) h, -2.0, 2.0, -10.0, 10.0);
}

void timer ( )
{
    clock_t now = clock ( ) ;
    static clock_t last = 0 ;
    
    if ( ( now - last ) / ( ( float ) CLOCKS_PER_SEC ) > 1 / 300.0 )
    {
        dg++;
        dg %= 360 ;
        last = now ;
    }
    glutPostRedisplay ( ) ;
}
int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(500,500);
    glutCreateWindow("3D Gasket");
    glutReshapeFunc(myReshape);
    glutDisplayFunc(display);
    glutIdleFunc(timer);
    glEnable(GL_DEPTH_TEST);
    glClearColor(1.0, 1.0, 1.0, 1.0);
    glutMainLoop();
    
    return 0;
}