Hi Andrei,

> But when I draw second curve I got that twisted result.

What twisted result is that? Sorry but I'm not understanding this part. What kind of twisting are you seeing?


> I need it to have ability to modify surface by moving points after it was trimmed.

Usually you will need to delete the surface, re-loft it and retrim it for this to happen.



> Is it any way to align second curve that was drawn to get not twisted result?

There isn't really any way to do this. If you want to do a lot of surface control point editing, probably a sub-d modeling package is a better fit for that kind of workflow.



> And could you pleas tell me the logic that used to create seam. As I can
> see it is not lay where curves was closed.

Right, it does not use the natural closing point of the curve because that would often generate a twisted result. Like in your case here the natural closing point of each curve are on these spots here (points created by MarkCurveStart command from http://moi3d.com/forum/index.php?webtag=MOI&msg=5288.21):



See how the start point of each of those curves is in a totally different location? One on the top, the next one on the bottom, other ones on one side - if Loft tried to just directly connect those curves together into a surface the surface would be really messed up with a severely twisted and knotted up type form to it.

So when closed curves are lofted there is a twist minimization stage done which determines a better seam spot on each curve. This analysis works by connecting together pairs of profiles with line segments between them and looking at the total length of the line segments, it then looks at potential seam locations and narrows down to the location that reduces the length of the connecting line segments. The very first curve will have its seam stay in its natural location but all the other ones after that will have adjusted seam spots in order to minimize twist in the connection.

- Michael