In Rhino I was able to loft from any shape (a closed curve in 3D or 2D) through another shape (closed curve again) above it. This would result in a closed surface that would start at the first shape and smoothly pass through the 2nd shape without a cap or cover surface, just a very nice transition all in one surface. It was a type of loft operation, although it might work better as a bulge with CU. There are several options to modify the transition as well. It was very useful for creating organic surfaces with some control. I think that one could reference several closed curves and the surface would build up to and through those shapes, also all enclosed (usually one surface). I sure would love to have this kind of tool in CU. Thanks

lofting from large blue circle through the smaller blue circle would result in a surface that would look like the gray curves (if the gray curves were U V curves on a surface). I tried to attach an example of this as a PNG file.
This is a simplified example.
[ATTACH]83[/ATTACH]

Hi again Tem

seems there are multiple ways of attacking this

the point at the summit will help. (use the point to substitute for a curve

- you could network surface - but you'd have to do it in 2 half domes

- you could skin it (circle, circle, point)

- you could skin with rails. you may have to split the circles to do this - again in sections

- you could cover surface with guides - and just include everything as your guides - it doesn't seem to matter if they meet the perimeter curve, so include the inner circle, point and the guides - for a clean surface however, be smart about using as little internal geometry as can possibly be used to correctly describe the shape you're after

Dont forget that some surface tools have 'advanced options' available on pressing 'option' ('ctrl' for PC)

You might want to explore the cover with guides tool. Attached is a file using the large circle as the cover and all the other curves as guides

This seems like a classic example for a surface that can be build using cover with guides...

Ciao, Norbert

In any case You are completly right that Your suggestion would be a welcome addition to CU's surface feature set.
If it works in other programs, why shouldn't it in CU?

Speaking of suggestions:
Similarily to Your closed loft, I'd like to suggest a closed net surface.
This would allow closed net curves to result in closed, continuous net surfaces. (I hope I explained myself?! Tim, if You need an example let me know!)

Ciao, Norbert