/*  Light1.c   This programs draws a simple Solar system that animates
    constantly
*/ 

#include <math.h>
#include <stdlib.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>

static void Init() {                                 // Initialization routine
  GLfloat mat_specular[] = {1.0, 1.0, 1.0, 1.0};     // Define highlight properties
  GLfloat mat_shininess[]= {50.0};                   // Define shininess of surface
  GLfloat light_position[] = {10.0, 40.0, 1.0, 0.0}; // Define light source position
  glClearColor(0.3, 0.3, 0.3, 0.0);                  // Set background to gray
  glShadeModel(GL_SMOOTH);                           // Smooth transitions between edges
  glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);   // Set material properties
  glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess); // Set material properties
  glLightfv(GL_LIGHT0, GL_POSITION, light_position);   // Set light properties
  glColorMaterial(GL_FRONT,GL_DIFFUSE);                // Set Color Capability

  glEnable(GL_COLOR_MATERIAL);		       // Enable color
  glEnable(GL_LIGHTING);		       // Enable lighting for surfaces
  glEnable(GL_LIGHT0);			       // Enable light source
  glEnable(GL_DEPTH_TEST); 		       // Enable depth buffering
}

static void Reshape(int width, int height) {         //  Determines Projection type
  glViewport(0, 0, (GLsizei)width, (GLsizei)height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(60.0, (GLfloat)width / (GLfloat)height, 1.00, 30.0);
  // Perspective Parms( Angle, Aspect Ratio, Front Clipping, Back Clipping)

  gluLookAt(0.0, 2.5, 3.0, 0.0, -0.5, -1.0, 0.0, 1.0, 0.0);
  // LookAt Parms (Eye_X, Eye_Y, Eye_Z, View_X, View_Y, View_Z, Up_X, Up_Y, UpZ)

  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glLoadIdentity();
}

static void display() {
  static double x; // This value will be remembered each time display is called
  x+=5; // Increment 5 degrees each call
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );  // Clear Color and Depth
  glPushMatrix();              		// Begin drawing image
    glRotatef( x,0.0,1.0,0.0);  	// Rotate
    glColor3f(1.0,0.0, 0.0);		// Set Drawing Color to Red
    glutSolidSphere(0.7,30,20);		// Draw Sphere(Radius, Slices, Stacks)
    glPushMatrix();			  // Draw orbiting planet
      glTranslatef(0.5,0.0,-1.0);	  // Move away from origin
      glColor3f(1.0,1.0,0.0);             // Set color to yellow
      glutSolidSphere(0.3,20,16);	  // Draw Sphere
      glPushMatrix();			     // Draw Moon
        glRotatef( x, 0.0, 1.0, 0.0);	     // Rotate
        glTranslatef(0.3,0.0,-0.5);	     // Move reference point
        glColor3f(0.0,0.0,1.0);		     // Color Blue
        glutSolidSphere(0.2,20,16);	     // Draw Sphere
      glPopMatrix();			  // Return to former reference
    glPopMatrix();			// Return to first refernce
    glPushMatrix();			  // Draw orbiting planet
      glTranslatef(-0.5,0.0,1.0);	  // Move reference poit
      glColor3f(0.0,1.0,0.0);		  // Set color to green
      glutSolidSphere(0.3,20,16);	  // Draw sphere
    glPopMatrix();			// Return to first reference
  glPopMatrix();		      // Return to base reference
  glFlush();			      // Flush drawing routines
  glutSwapBuffers();		      // Swap buffers
  glutPostRedisplay();		      // Display results
}

int main(int argc, char** argv) {	// Run program with possible parameters
// "glut" Initialization Functions rather than "aux" versions
  glutInit(&argc,argv);  
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH ); // Initialize modes
  glutInitWindowSize( 550, 550);
  glutInitWindowPosition( 50, 50);
  glutCreateWindow( argv[0]); // Note that arg[0] is name of program (Window name)
  Init();
  glutDisplayFunc(display);
  glutReshapeFunc(Reshape);
  glutMainLoop();
  return 0;
}