surface normal

Meanings

1. A unit vector at any given point P of a surface M which is perpendicular to the tangent plane T_P(M) of M at P. For a surface with parametrization ⃑x(u,v), it is given by
2. A unit vector at any given point P of a surface M which is perpendicular to the tangent plane T_P(M) of M at P. For a surface with parametrization ⃑x(u,v), it is given by ⃑n=±⃑x_u×⃑x_v/ lVert ⃑x_u×⃑x_v rVert where the sign can be chosen at will.
3. ⃑n=±⃑x_u×⃑x_v/ lVert ⃑x_u×⃑x_v rVert
4. where the sign can be chosen at will.