maybe it's a chance, if you insect 3 planes, and then use the
min/max_extend-functions... it could be, that one of the ext-
ends gives you the point, you're looking for ...
... but you'd have to do this for every corner of your obj.
don't count on this, to work at all, as this is probably only
a silly idea, that flashed through my mind, when I read your
post ...
