// handles glut mouse movement events
void passiveMotion(int x, int y)
{
	// make sure we're not in the center
	if (x != 255 || y != 255)
	{
		vec3 rotation(0);
		rotation.x = -(255 - y);
		rotation.y = -(255 - x);
		camera.rotate(rotation);

		glutWarpPointer(255, 255);
	}
}