It's looking great from here.
The convex hull function creates surface around a selection of vertices. Imagine a balloon having the air let out of it, over a load of points - it will shrink until it can't any more. Any 'internal' points are not used to make the shape but any that touch the 'balloon' will define the outside of the new surfaces.
There's an example in the manual - access this from the Help menu inside AC3D. see Operations on Vertices->Create-convex surface/object.