static void draw(void)
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  glPushMatrix();
    glRotatef(view_rotx, 1.0, 0.0, 0.0);
    glRotatef(view_roty, 0.0, 1.0, 0.0);
    glRotatef(view_rotz, 0.0, 0.0, 1.0);

    glPushMatrix();
      glTranslatef(-3.0, -2.0, 0.0);
      glRotatef(angle, 0.0, 0.0, 1.0);
      glCallList(gear1);
    glPopMatrix();

    glPushMatrix();
      glTranslatef(3.1f, -2.f, 0.f);
      glRotatef(-2.f * angle - 9.f, 0.f, 0.f, 1.f);
      glCallList(gear2);
    glPopMatrix();

    glPushMatrix();
      glTranslatef(-3.1f, 4.2f, 0.f);
      glRotatef(-2.f * angle - 25.f, 0.f, 0.f, 1.f);
      glCallList(gear3);
    glPopMatrix();

  glPopMatrix();
}