Thank you very much Michael.

Bounding box is interesting information.

I have been having fun, after a circle sweep to a curve, moving the curve around the screen. [Or moving the circle around the screen...]
The 3D sweep follows along, (due to History I think), and changes to planar "envelope-ish" when part of the curve is in the (it turns out), Bounding Box of the circle.
(or is it when the circle is in the rail's bounding box...?) I am not sure... The curves bounding box seems to jump in size...?

The 2D "envelope-ish seems to have a bit extra at the beginning...
Including the center or point on the curve seems to have some effect on the sweep???

I'll have to read up on Bounding Box.

- Brian

So selecting multiple objects expands the (combined) boundary box to a rectangle, encompasing all of the objects.
Each object still has its own bounding box...

History is ended if the sweep result only is moved...