/* Sierpinski Pentagon GL program */


/* This program illustrates simple use of mouse with OpenGL
to start and stop program execution */

#include <GL/glut.h>

/* define a point data type */

typedef struct { float x,y;} point;

point vertices[5]={{50,0},{0,250},{250,500},{500,250},{450,0}}; /* A pentagon */

int j;
point new, old={75,50}; /* A random point */

void clear(void)
{
	glClear(GL_COLOR_BUFFER_BIT);
}

void display(void)

/* computes and plots a single new point */

{
	long random();
	int i;
	j=random()%5; /* pick a vertex at random */


/* Compute point halfway between vertex and old point */

	new.x = (old.x+vertices[j].x)/2; 
	new.y = (old.y+vertices[j].y)/2;
	
/* plot point */

	glBegin(GL_POINTS);
		glVertex2f(new.x, new.y);
	glEnd();


/* replace old point by new */

	old.x=new.x;
	old.y=new.y;
	

	glFlush();
}


void mouse(int btn, int state, int x, int y)
{
if(btn==GLUT_LEFT_BUTTON&state==GLUT_DOWN)  glutIdleFunc(display);
if(btn==GLUT_MIDDLE_BUTTON&state==GLUT_DOWN)   glutIdleFunc(NULL);
if(btn==GLUT_RIGHT_BUTTON&state==GLUT_DOWN)   exit();
}

int main(int argc, char** argv)
{


	glutInit(&argc,argv);
	glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
	glutInitWindowSize(500,500);
	glutInitWindowPosition(0,0);
	glutCreateWindow("Sierpinski Gasket");

	glutIdleFunc (display);
	glutMouseFunc (mouse);  
	glClearColor(1.0, 1.0, 1.0, 0.0); /* white background */
	glColor3f(1.0, 0.0, 0.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(0.0, 500.0, 0.0, 500.0, -1.0, 1.0);
	glMatrixMode(GL_MODELVIEW);
	glutDisplayFunc(clear);


	glutMainLoop();

}