Hi David,
> NOTE! Show/hide points doesn't work for boxes being made
> from extruded rectangles.
Check out this FAQ item:
Why does show points work for some objects but not others?
That tries to explain why you can't turn on points for solids that have trimmed surfaces inside of them.
But like Burr mentions, if you use Edit/Separate to break a solid into individual surfaces, then you can always turn on points for individual surfaces, and then use Edit/Join to glue them back together at the end.
Basically when you do an extrude of a rectangle, when the "cap" surfaces on the top and bottom are created they are created as larger planes that have trim curves on them. If you zoom out a little bit when you turn on the points after using Edit/Separate you'll see the points for the plane which is somewhat extended.
That's because that capping procedure works on any kind of planar curve, which can have a much more complex outline than just a rectangle.
At any rate - unfortunately the basic mechanics behind how NURBS solids work (with trimmed and joined edges with "underlying surfaces", some illustration of that in that above FAQ answer) does not really lend itself very well to deforming things by pulling points around, when you have trimmed edges that are joined to one another.
If you do want to focus a lot on pulling points around on solids for getting things done, you may actually be better of with a polygon modeling program instead where things are set up to work like that.
But there is also a benefit of the way NURBS solids are set up, which is that they work a lot better with boolean operations than a polygon modeling setup.
With a NURBS modeler, when you do a boolean between 2 objects, the actual underling surfaces stay the same and only new trim curves are calculated. This tends to help keep surfaces as more simple larger sheets. With a polygon modeler, booleans tend to make a big mess, with more and more little fragmented facet pieces being generated on each cut.
- Michael
