planet.c

// from the OpenGL Redbook
// creates a simple 3D solar system, with keyboard interactions
// use the 'd' and 'y' keys to interact with the environment

#include <GL/glut.h>

static int year = 0, day = 0;

void init(void){
  glClearColor(0.0, 0.0, 0.0, 0.0);
  glShadeModel(GL_FLAT);
}

void display(void){
  glClear(GL_COLOR_BUFFER_BIT);
  glColor3f(1.0, 1.0, 1.0);
  
  glPushMatrix();
  
  // draw sun
  glutWireSphere(1.0, 20, 16);
  glRotatef((GLfloat) year, 0.0, 1.0, 0.0);
  glTranslatef(2.0, 0.0, 0.0);
  glRotatef((GLfloat) day, 0.0, 1.0, 0.0);
  
  // draw smaller planet
  glutWireSphere(0.2, 10, 8);
  glPopMatrix();
  glutSwapBuffers();
}

void reshape(int w, int h){
  glViewport(0, 0, (GLsizei) w, (GLsizei) h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(60.0, (GLfloat) w / (GLfloat) h, 1.0, 20.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  gluLookAt(0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
}

void keyboard(unsigned char key, int x, int y){
  switch(key){
    case 'd':
      day = (day + 10) % 360;
      glutPostRedisplay();
      break;
    case 'D':
      day = (day - 10) % 360;
      glutPostRedisplay();
      break;
    case 'y':
      year = (year + 5) % 360;
      glutPostRedisplay();
      break;
    case 'Y':
      year = (year - 5) % 360;
      glutPostRedisplay();
      break;
    default:
      break;
  }
}

int main(int argc, char** argv){
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
  glutInitWindowSize(500, 500);
  glutInitWindowPosition(100, 100);
  glutCreateWindow(argv[0]);
  init();
  glutDisplayFunc(display);
  glutReshapeFunc(reshape);
  glutKeyboardFunc(keyboard);
  glutMainLoop();
  return 0;
}