//********************************************************************y
// simple planetary system:
// a spinning yellow moon orbiting around a red sun
// Demonstrates:
// modelling and transformations use, animation, use of double buffering, 
// depth buffer use,
// and idle callback
// Modified from the Red Book example
// GK. 10/9/2003
//********************************************************************

#include<iostream.h>
#include<stdio.h>
#include<GL/glut.h>
#include<math.h>


// *********** Global declarations and named constants ****************

#define RADMOON 0.3
#define RADSUN 1.0
#define RADORBIT 3.0
 
static int day,  //rotation angle fro moon spin
           year; //rotatoon angle for mmon orbiting around the sun

// ********* Prototypes ************************************************

void  myinit();
void  display();
void idle();

// ****************************************************************************		
void myinit()
{
	// we will make a transparent polyhedra, so we will use the alpha value for blending
	glClearColor(0.0, 0.0, 0.0,0.0);
   
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(-2.25*RADORBIT,2.25*RADORBIT,-2.25*RADORBIT,2.25*RADORBIT, -2.25*RADORBIT,2.25*RADORBIT);
	glMatrixMode(GL_MODELVIEW);

	glEnable(GL_DEPTH_TEST); // use Z-buffering
}

//****************************************************************************
// updates rotating angles
void idle()
{
	day = (day+5)%360;
	year=(year+1)%360;
	glutPostRedisplay();

}
// ****************************************************************************
void display()
{
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
	glPushMatrix();

        glRotatef(75, 1, 0, 0);                            // change view

	glColor3f(1.0, 0.0, 0.0);
	glutWireSphere(RADSUN, 20, 16);  // draw sun

        //instantiate moon in orbit
	glRotatef( year,  0, 0, 1);
	glTranslatef(RADORBIT, 0, 0);
	glRotatef(day, 0,0,1);
	glColor3f(1.0, 1.0, 0.0);
	glutWireSphere(RADMOON, 10, 8);  // draw moon

        glPopMatrix();
        glutSwapBuffers();
}

// ********* main()**************
int main(int argc, char **argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_DEPTH);
	glutInitWindowSize(500,500);
	glutInitWindowPosition(0,0);
	glutCreateWindow("Solar System");
	glutDisplayFunc(display);
	glutIdleFunc(idle);
	myinit();
	
	glutMainLoop();

	return 0;
}