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

/*
In this lab, we will create an OpenGL program to look at the 2D Sierpinski Gasket

  #1
  Note that the WINDOW pre-processor #define is 500.  Set up your window using
  this parameter, so the window is 500 x 500, but with the origin, (0,0) in the 
  center.


  #2
  Determine coordinates for an isoceles triangle that will fit in your window.
  By isoceles we mean equal length edges.  You should then enter these coordinates
  in the vertices array.  It's 3 rows (for 3 points), and 2 columns (x and y coord).

  You should also pick one, initial point in your triangle, and enter the coordinates 
  in the array p.


  #3
  Complete the loop rendering 100 points inside the triangle, based on our in-class
  discussion (and textbook).  Note that the vector version of glVertex2f is used.


  #4
  Modify your code so that clicking on the left mouse button will render an
  additional 100 points, preserving the points already rendered.  
*/



// make your intial window size a pre-processor definition
#define WINDOW 500

GLint clear=1;
GLfloat vertices[3][2]={ {-0.87*WINDOW/4 , -WINDOW/4} 
					   , { 0.87*WINDOW/4 , -WINDOW/4}
					   , { 0 , WINDOW/4} };

GLfloat p[2] = { 0 , 0 };



void myInit() {
	glClearColor(1,1,1,0);
	glColor3f(1,0,0);
	glPointSize(2);

	// clipping window here
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(-WINDOW/2,WINDOW/2,-WINDOW/2,WINDOW/2);
	glMatrixMode(GL_MODELVIEW);
}

void display ()
{
	if (clear==1) glClear(GL_COLOR_BUFFER_BIT);
	
	GLint j,k;

	glBegin(GL_POINTS);
	for (k=0; k<100; k++) {
		// first, pick a random vertex from 0, 1, or 2
		j = rand()%3;
		// now, compute the next point
		p[0] = (p[0] + vertices[j][0])/2;
		p[1] = (p[1] + vertices[j][1])/2;
		// display the new point
		glVertex2fv(p);
	}
	glEnd();

	glFlush();
}

void mouse (int btn, int state , int x, int y)
{
	if (btn==GLUT_LEFT_BUTTON && state == GLUT_DOWN) {
		clear=0;
		display();
	}
	if (btn==GLUT_RIGHT_BUTTON && state==GLUT_DOWN) {
		exit(0);
	}
}

int main (int argc, char **argv)
{
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB );
	glutInitWindowSize(WINDOW,WINDOW);
	glutCreateWindow("2D Gasket");
	glutDisplayFunc(display);
	glClearColor(1.0,1.0,1.0,0.0);
	glutMouseFunc(mouse);
	myInit();
	glutMainLoop();

	return 0;
}