> However, unless the equation is normalized, the distance could be scaled in unusual ways that are less than useful. > > []the[] point not on a plane will eva

> However, unless the equation is normalized, the distance could be scaled in unusual ways that are less than useful. > > []the[] point not on a plane will evaluate to 1 They mean the vertex (of the tetrahedron). The signed distance function is scaled such that the (single remaining) vertex that isn't at distance 0 (by construction) will instead be at distance 1. So the distance is always scaled in a unique well-defined way (assuming not all four points are coplanar). Whether that way of scaling is useful depends on your use case, of course.