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

GLfloat light0_ambient[] =
{0.2, 0.2, 0.2, 1.0};
GLfloat light0_diffuse[] =
{0.0, 0.0, 0.0, 1.0};
GLfloat light1_diffuse[] =
{1.0, 0.0, 0.0, 1.0};
GLfloat light1_position[] =
{1.0, 1.0, 1.0, 0.0};
GLfloat light2_diffuse[] =
{0.0, 1.0, 0.0, 1.0};
GLfloat light2_position[] =
{-1.0, -1.0, 1.0, 0.0};
float s = 0.0;
GLfloat angle1 = 0.0, angle2 = 0.0;

void 
output(GLfloat x, GLfloat y, char *text)
{
  char *p;

  glPushMatrix();
  glTranslatef(x, y, 0);
  for (p = text; *p; p++)
    glutStrokeCharacter(GLUT_STROKE_ROMAN, *p);
  glPopMatrix();
}

void 
display(void)
{
  static GLfloat amb[] =
  {0.4, 0.4, 0.4, 0.0};
  static GLfloat dif[] =
  {1.0, 1.0, 1.0, 0.0};

  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glEnable(GL_LIGHT1);
  glDisable(GL_LIGHT2);
  amb[3] = dif[3] = cos(s) / 2.0 + 0.5;
  glMaterialfv(GL_FRONT, GL_AMBIENT, amb);
  glMaterialfv(GL_FRONT, GL_DIFFUSE, dif);

  glPushMatrix();
  glTranslatef(-0.3, -0.3, 0.0);
  glRotatef(angle1, 1.0, 5.0, 0.0);
  glCallList(1);        /* render ico display list */
  glPopMatrix();

  glClear(GL_DEPTH_BUFFER_BIT);
  glEnable(GL_LIGHT2);
  glDisable(GL_LIGHT1);
  amb[3] = dif[3] = 0.5 - cos(s * .95) / 2.0;
  glMaterialfv(GL_FRONT, GL_AMBIENT, amb);
  glMaterialfv(GL_FRONT, GL_DIFFUSE, dif);

  glPushMatrix();
  glTranslatef(0.3, 0.3, 0.0);
  glRotatef(angle2, 1.0, 0.0, 5.0);
  glCallList(1);        /* render ico display list */
  glPopMatrix();

  glPushAttrib(GL_ENABLE_BIT);
  glDisable(GL_DEPTH_TEST);
  glDisable(GL_LIGHTING);
  glMatrixMode(GL_PROJECTION);
  glPushMatrix();
  glLoadIdentity();
  gluOrtho2D(0, 1500, 0, 1500);
  glMatrixMode(GL_MODELVIEW);
  glPushMatrix();
  glLoadIdentity();
  /* Rotate text slightly to help show jaggies. */
  glRotatef(4, 0.0, 0.0, 1.0);
  output(200, 225, "This is universe.");
  glDisable(GL_LINE_SMOOTH);
  glDisable(GL_BLEND);
  output(160, 100, "spinning toruses");
  glPopMatrix();
  glMatrixMode(GL_PROJECTION);
  glPopMatrix();
  glPopAttrib();
  glMatrixMode(GL_MODELVIEW);

  glutSwapBuffers();
}

void 
idle(void)
{
  angle1 = (GLfloat) fmod(angle1 + 0.8, 360.0);
  angle2 = (GLfloat) fmod(angle2 + 1.1, 360.0);
  s += 0.05;
  glutPostRedisplay();
}

void 
visible(int vis)
{
  if (vis == GLUT_VISIBLE)
    glutIdleFunc(idle);
  else
    glutIdleFunc(NULL);
}

int 
main(int argc, char **argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  glutCreateWindow("universe");
  glutDisplayFunc(display);
  glutVisibilityFunc(visible);

  glNewList(1, GL_COMPILE);  /* create ico display list */
  glutSolidTorus(0.75, 0.85, 3, 15);
  glEndList();

  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glLightfv(GL_LIGHT0, GL_AMBIENT, light0_ambient);
  glLightfv(GL_LIGHT0, GL_DIFFUSE, light0_diffuse);
  glLightfv(GL_LIGHT1, GL_DIFFUSE, light1_diffuse);
  glLightfv(GL_LIGHT1, GL_POSITION, light1_position);
  glLightfv(GL_LIGHT2, GL_DIFFUSE, light2_diffuse);
  glLightfv(GL_LIGHT2, GL_POSITION, light2_position);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_CULL_FACE);
  glEnable(GL_BLEND);
  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
  glEnable(GL_LINE_SMOOTH);
  glLineWidth(2.0);

  glMatrixMode(GL_PROJECTION);
  gluPerspective( /* field of view in degree */ 40.0,
  /* aspect ratio */ 1.0,
    /* Z near */ 1.0, /* Z far */ 10.0);
  glMatrixMode(GL_MODELVIEW);
  gluLookAt(0.0, 0.0, 5.0,  /* eye is at (0,0,5) */
    0.0, 0.0, 0.0,      /* center is at (0,0,0) */
    0.0, 1.0, 0.);      /* up is in positive Y direction */
  glTranslatef(0.0, 0.6, -1.0);

  glutMainLoop();
  return 0;             /* ANSI C requires main to return int. */
}