Hi Phil - the Loft command only takes one set of cross-section curves and constructs a surface through that, so for doing a Loft for example you would only be able to select just the Red curves that you are showing there for making a Loft.

You're getting a weird result in your case there because Loft is trying to build a surface that swoops through each of those curves, like it's trying to go straight from one of your red curves directly to one of the blue curves. That makes the surface suddenly swoop around as it tries to use such different shapes as the same kind of cross-section.


There are other commands that take different curve structures - Network for example can take 2 sets of cross-sections that cross each other. Sweep takes cross sections plus one or two rail curves.

But really it's usually not a good idea to try and build something like what you're showing there with tight bends in the corners just out of one single surface, usually a single surface should be something more like one sheet of material that does not have any really tight bends in it. Tight bends like the corner areas you have in this case are usually better put in as initially sharp corners and then use the Fillet command to round them off, rather than trying to build a surface that directly incorporates such a tight bend in shape directly in the surface itself.

This kind of model that you happen to be targeting is actually a pretty advanced style of mdoel to work with - things that are semi blobby and melty looking tend to be difficult to create using NURBS modeling techniques and can be a better fit for a sub-d polygon type modeling environment instead.


See here for some examples of different strategies for this kind of thing:

http://moi3d.com/forum/index.php?webtag=MOI&msg=1002.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=3137.1



Also another approach is to build it by Loft, but using vertically oriented sections, as shown here (this way does do it all as a single surface):
http://moi3d.com/forum/index.php?webtag=MOI&msg=6134.6

To use that method you would include a point object (created by Draw curve > More > Point) at the top in the same plane as the topmost profile, and select the point object during the Loft as well (telling the loft to end in that point), and then use Loft style = "Loose" in the Loft options. If you're going to try to build something kind of smooth and blobby all in one single surface that method taends to be the best way. See here for some more examples:
http://moi3d.com/forum/index.php?webtag=MOI&msg=6639.2
Loft to point is new in version 3 so make sure you're running the current v3 beta in order to make use of this method.


Hope this helps!

- Michael