Lofting the surface made of curves

[djole]

I want to loft the surface, made of polylines.

The problem is that, when I select all the splines, and then do Draw-> Modeling -> Loft then I chose the "Cross-section only", this what kind of message I get in command box:

 

The selected entities are not valid.

Why is this happening?

 

Here the .dwg file with the mentioned splines in it:

 

http://www.gamefront.com/files/20173365/Kopie+von+Vorl%C3%A4ufiger+H%C3%B6henplan+H%C3%B6henbahn+Seenplateau.dwg

Edited March 31, 2011 by djole

[ReMark]

Can you post the dwg file here? It would be a big help. Thanks.

[djole]

I tried doing it, but I can not attach it. The .dwg file is too big - 3MB, even when I zip it, it takes around 2MB, which is again too large for attachment.

 

Can't you download it from the above link:

 

http://www.gamefront.com/files/20173365/Kopie+von+Vorl%C3%A4ufiger+H%C3%B6henplan+H%C3%B6henbahn+Seenplateau.dwg

[djole]

this is what I get when I try to loft the polylines:

 

Command: _u Loft GROUP

Command:

Command:

Command: _qsave

Command:

Command:

Command: _loft

Select cross-sections in lofting order: Specify opposite corner: 86 found

 

Select cross-sections in lofting order:

 

Enter an option [Guides/Path/Cross-sections only] : C

 

 

Modeling Operation Error:

Surface U and V derivatives are in the same or opposite direction.

 

 

 

Modeling Operation Error:

Surface U and V derivatives are in the same or opposite direction.

 

The selected entities are not valid.

 

I want to create a surface or solid out of those polylines (a montain slope). How can I do that?