/***************************************************
Movement Example Four 
Program that demonstrates using PushMatrix and PopMatrix
for VERY complex movements.
A moving grey cone is orbited by a red donut.  Green
and blue balls spin in and out of the donut.
**************************************************/
#include <GL/glut.h>
#include <stdlib.h>

// X and Y location, donut spin, sphere one and two spin
float X=-50.0,Y=-20.0,dspin=0.0,s1spin=0.0, s2spin;

/*************************************************************************/
void display(void)
{
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glEnable(GL_DEPTH_TEST);

   glPushMatrix();                // save identity state
   glTranslatef(X,Y,0.0);         // move the whole scene to X,Y
   glPushMatrix();                // save this movement
      glRotatef(-90, 1, 0, 0);    // stand up the cone
      glColor3f(0.7,0.7,0.7);
      glutSolidCone (3,15,20,10); // draw the gray cone
   glPopMatrix();                 // go back to movement without rotation

   glRotatef(dspin, 0, 1, 0);     // spin the donut about Y axis
   glTranslatef(20, 5, 0.0);      // move the donut away from cone

   glPushMatrix();                // save this transformation
     glTranslatef( 0, 7, 0);      // move the red ball up to top of ring
     glRotatef(s1spin,1,0,0);     // spin the red sphere about X
     glTranslatef( 0, 5, 0);      // radius of ball's orbit is 5 
     glColor3f(0.2,0.8,0.5);
     glutSolidSphere(4,10,10);    // draw the red ball
   glPopMatrix();                 // go back to previous transformation state

   glPushMatrix();                // save this transformation
     glTranslatef( 7, 0, 0);      // move the blue ball up to side of ring
     glRotatef(s2spin,0,1,0);     // spin the blue sphere about Y
     glTranslatef( 5, 0, 0);      // radius of ball's orbit is 5 
     glColor3f(0.2,0.3,0.9);
     glutSolidSphere(4,10,10);    // draw the blue ball
   glPopMatrix();                 // go back to previous transformation state

   glColor3f(0.9,0.3,0.2);
   glutSolidTorus(1,6,20,30);     // draw the donut

   glPopMatrix();                 // go back to identity matrix
   glutSwapBuffers();
   glFinish();
}

/*************************************************************************/
void reshape(int w, int h)
{
   glViewport (0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(-50.0, 50.0, -50.0, 50.0, -50.0, 50.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}
/*************************************************************************/
void animate()
{
  X += 0.2;
  Y += 0.1;
  dspin += 3;
  s1spin += 11;
  s2spin += 23;
  if (X > 60) 
      X = -60.0;
  if (Y > 60) 
      Y = -60.0;
  glutPostRedisplay();
}
/*************************************************************************/
/*************************************************************************/
int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize (450, 450); 
   glutInitWindowPosition (100, 100);
   glutCreateWindow (argv[0]);
   glutDisplayFunc(display); 
   glutReshapeFunc(reshape); 
   glutIdleFunc(animate); 
   glutMainLoop();
   return 0;   
}