Hi,   As some of you (the most curious) asked me why I prefered to implement a dedicated normal computation for the Cylinder, I'll try to explain this with some PG.   Note : all I'll show here with a ribbon is the same with any mesh built with the same way, it is to say some laces between two pools of vertices (plane, ground, etc). And it only concerns some vertices on the edges (if any), those belonging to 3 faces only.   Let's go. Here is a flat ribbon : http://www.babylonjs-playground.com/#G6