TGeoVolume *ggg = geom->MakeSomething( …)
So the question is - how to find not only points of shape but its faces also? (in wich sequence the points should be connected?)
You have too look in TGeoPainter::PaintWhatever to see how points are connected and how segments make faces for each specific shape.
what about Pgon? there is no PaintPgon method.
Pgon is paint exactly like a Pcon, just the number of segments is different - look at PaintPcon()