/* gasket2.c   */

/* E. Angel, Interactive Computer Graphics */
/* A Top-Down Approach with OpenGL, Third Edition */
/* Addison-Wesley Longman, 2003 */
/* Recursive subdivision of triangle to form Sierpinski gasket */#include <GL/glut.h>typedef float point2[2];/* initial triangle */point2 v[]={{-1.0, -0.58}, {1.0, -0.58}, {0.0, 1.15}};int n;void triangle( point2 a, point2 b, point2 c)/* display one triangle  */{    glBegin(GL_TRIANGLES);       glVertex2fv(a);       glVertex2fv(b);       glVertex2fv(c);    glEnd();}void divide_triangle(point2 a, point2 b, point2 c, int m){/* triangle subdivision using vertex numbers */    point2 v0, v1, v2;    int j;    if(m>0)     {        for(j=0; j<2; j++) v0[j]=(a[j]+b[j])/2;        for(j=0; j<2; j++) v1[j]=(a[j]+c[j])/2;        for(j=0; j<2; j++) v2[j]=(b[j]+c[j])/2;        divide_triangle(a, v0, v1, m-1);        divide_triangle(c, v1, v2, m-1);        divide_triangle(b, v2, v0, m-1);    }    else(triangle(a,b,c)); /* draw triangle at end of recursion */}void display(void){//	glLogicOp(GL_XOR);//    glClear(GL_COLOR_BUFFER_BIT);//	divide_triangle(v[0], v[1], v[2], n);//    glFlush();}


void mouse(int btn, int state, int x, int y)
{
	if(btn==GLUT_LEFT_BUTTON&&state==GLUT_DOWN)
	{	glLogicOp(GL_XOR);
		divide_triangle(v[0], v[1], v[2], n);
		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(1.0,0.0,0.0);

	glEnable(GL_COLOR_LOGIC_OP);
	glClear(GL_COLOR_BUFFER_BIT);}voidmain(int argc, char **argv){    n=4;    glutInit(&argc, argv);    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB );    glutInitWindowSize(500, 500);    glutCreateWindow("3D Gasket");    glutDisplayFunc(display);
	glutMouseFunc(mouse);	myinit();    glutMainLoop();}