gistfile1.c

{
    float rotstep = ((M_PI / 2.) / 9.) / 2.;
    
    GLKVector2 ndir = GLKVector2Normalize(direction);
    _rx += ndir.y * rotstep;
    if (_rx > M_PI_2)
        _rx = M_PI_2;
    if (_rx < -M_PI_2)
        _rx = -M_PI_2;
    _ry += ndir.x * rotstep;
    if (_ry > M_PI)
        _ry -= 2 * M_PI;
    if (_ry < -M_PI)
        _ry += 2 * M_PI;
}