Hi Rudl,

> it seems I have understand an imported thing. When I
> did a surface I have the surface with it´s own edges
> and also the original edges. Is this right?

Yes, that's correct. But just to be clear the name "Edge" in MoI means something different than just "Curve".

A curve is a wire-like object that you initially draw like lines or arcs or control point curves, etc...

Surfaces can be constructed from curves and each surface has a trimming boundary that defines which part of the surface is active and which parts are holes within the surface area.

Those trimming boundaries are made up of "Edge" objects. They are wire-like objects like curves (and in fact you can select them to be used by several commands as if they were a curve like you can extrude them, etc...) but the difference is that they are not a complete "top level" object all by themselves, they are actually a kind of child of the surface object.

Some commands work by selecting "edge" objects specifically, and some may give you some different results depending on whether a standalone curve object was selected or whether edges were selected.

If you have the original curve objects sitting in the exact same area as an edge, it can make it difficult to select the edge instead of the curve object. In cases like that you want to hide or delete the original curve objects so that they do not interfere with selection of the edge.

Blend for example is a command that does different things depending on whether you give it a curve selection or an edge selection.

If you select 2 curve objects, then when you do Blend it will build a blend curve result between their endpoints like this:



That is what it was trying to do in your particular case, and because you had 2 curves that did not have any empty space in between their endpoints it would have been difficult to see any result there.

If you select 2 surface edges then Blend will build a blend surface that comes away from the edge, like this instead:



- Michael