title: AddTo3DScene
author: tiglari

AddTo3DScene is the method of map objects whereby the map structure
builds the 3d scene.  The real work is done by methods such as
TFace.AddTo3DScene in prog/QkMapPoly.pas [tig: what is the correct name for
a subclass's implementation of a virtual method?]; we see that
the workhorse line is:

        CurrentMapView.Scene.AddPolyFace(P);

CurrentMapView is a global variable of type TPyMapView defined by
this line of python/PyMapView.pas:

 CurrentMapView : TPyMapView = TPyMapView(-1);

A TPyMapView is a subclass of TScrollBox, I presume the -1 is setting
its owner to nothing [tig: check this].  For some reason, Scene is a property
whose read method is FScene, whose value is a TSceneObject.
