moveLight.c

// from the OpenGL Redbook
// a moving light around a torus

#include <GL/glut.h>

static int spin = 0;

void init(void){
  glClearColor(0.0, 0.0, 0.0, 0.0);
  glShadeModel(GL_SMOOTH);
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glEnable(GL_DEPTH_TEST);
}

// light position is reset after modeling transofmration (glRotated) is called
// places light at new position in world coordinates, cube represents position of light
void display(void){
  GLfloat position[] = {0.0, 0.0, 1.5, 1.0};
  
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glPushMatrix();
  glTranslatef(0.0, 0.0, -5.0);
  
  glPushMatrix();
  glRotated((GLdouble) spin, 1.0, 0.0, 0.0);
  glLightfv(GL_LIGHT0, GL_POSITION, position);
  
  glTranslated(0.0, 0.0, 1.5);
  glDisable(GL_LIGHTING);
  glColor3f(0.0, 1.0, 1.0);
  glutWireCube(0.1);
  glEnable(GL_LIGHTING);
  glPopMatrix();
  
  glutSolidTorus(0.275, 0.85, 8, 15);
  glPopMatrix();
  glFlush();
}

void reshape(int w, int h){
  glViewport(0, 0, (GLsizei) w, (GLsizei) h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  
  gluPerspective(40.0, (GLfloat) w / (GLfloat) h, 1.0, 20.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

void mouse(int button, int state, int x, int y){
  switch(button){
    case GLUT_LEFT_BUTTON:
      if(state == GLUT_DOWN){
        spin = (spin + 30) % 360;
        glutPostRedisplay();
      }
      break;
    default:
      break;
  }
}

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