I am going to make both covers of this one made of duvet.

[LeeJaeYoung]

I am going to make both covers of this one made of duvet.
I thought I would do it with Prisim_'s Si, so I wrote it first.
I couldn't control the inside of the tube.
How should I approach it?

One exterior was almost fitted.
But the inside is unimaginable.
I would be grateful if you could tell me how.

Did you have to do everything with prism_?

[Botonis]

I am not sure if I got it right but in case you want to create a hollow area inside I would use a shell with the same shape and trim the inside area.

Give the shape of the shell in a section.