// header files
#include <iostream>
#include <GL/glut.h>



// function prototypes
void display(void);
void reshape(int width, int height);
void init();



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

  // initialize glut 
  glutInit(&argc, argv);

  // set window size
  glutInitWindowSize(600,600);

  // establish glut display parameters
  glutInitDisplayMode(GLUT_DOUBLE   | GLUT_RGB  |GLUT_DEPTH);

  // create window
  glutCreateWindow("My Second OpenGL program");

  // register callback functions
  glutDisplayFunc(display);
  glutReshapeFunc(reshape); 


  // initalize opengl parameters
  init();

  // loop until something happens
  glutMainLoop();
  return 0;           
}

void init()
{



  // initialize viewing system
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(20.0, 1.0, 1.0, 100.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();

  // initialize background color to black
  glClearColor(0,0,0,0);

	// enable depth buffering
 	glEnable(GL_DEPTH_TEST);
}




void reshape(int width, int height)
{
	if (width<height)
		glViewport(0,0,width,width);
	else
		glViewport(0,0,height,height);

}

void display()
{

// clear buffers
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// initialize modelview matrix
	glMatrixMode(GL_MODELVIEW_MATRIX);
	glLoadIdentity();

// translate everything in z
	glTranslatef(0,0,-10);

// draw Sphere
	GLfloat purple[] = {1,0,1,0};			// purple
	glColor4fv(purple);
	glutSolidSphere(1,100,100);


// draw Triangle strip
	GLfloat green[] = {0,1,0,0};			// gree 
	glColor4fv(green);
	glBegin(GL_TRIANGLE_STRIP);
	glVertex3f(-20.0,-1.0,-80.0);
	glVertex3f(-20.0,-1.0,0.0);
	glVertex3f(20.0,-1.0,-80.0);
	glVertex3f(20.0,-1.0,0.0);
	glEnd();

// swap buffers
	glutSwapBuffers();


	
}