HI All   I'm a 3D and Babylon newbie and am struggling with normals. I understand the concept of them (I think) and that in Babylon terms a normal is defined for each vertex, but I don't know what values to use to define those normals or how to calculate them.   Here is what I've been working on (a way of extruding an object from a 2d face):   http://jsbin.com/noquwehujudi/1/edit   The object is meant to be like a rectangular box with a rebate cut out of it and each "face" of that object