Hi SUIYAN,

re:
>（This is a boundary surface problem, and there is no corresponding processing tool in Moi.
> In Rhino, you should use the patch tool and then trim it. Please take a look at the pictures
> and demonstrate the process of gif.）

That's something that can be useful in certain cases but it's usually a better modeling technique in NURBS to form extended simplified 4 sided surfaces and then form the final boundary by a boolean operation.

- Michael