Return value of {@link #intersectRayAar(double, double, double, double, double, double, double, double, Vector2d)} and
{@link #intersectRayAar(Vector2d, Vector2d, Vector2d, Vector2d, Vector2d)}
to indicate that the ray intersects the side of the axis-aligned rectangle with the minimum y coordinate.
Return value of {@link #intersectRayAar(double, double, double, double, double, double, double, double, Vector2d)} and {@link #intersectRayAar(Vector2d, Vector2d, Vector2d, Vector2d, Vector2d)} to indicate that the ray intersects the side of the axis-aligned rectangle with the minimum y coordinate.