Something that collapses down to a point can cause problems for shelling and offsetting, particularly towards the inside and if the surface is not smooth at the point. The offset surface will get bunched up with pieces crossing over themselves:




For that particular kind of shape it can be better to do a curve offset and prepare the curve outline so that the result of the revolve has the thickness in it just with the revolve:



- Michael

Offsets of things that are smooth to each other will have the individual offset pieces naturally touch each other:






Offsets of things that are not smooth results in offset pieces that do not touch each other, they either cross each other or have a gap that needs to be filled in:


- Michael

I thought same but how explain this :

If I revolve the curve.
Save, exit, reopen and shell the surface, you don't have the problem...

 

So I think the shell on the revolving has a problem.
Perhaps a rest of history ?

Michael, could you test and see if this experience is same for you ?

Left a curve is revolved then shelled.

Right a curve has been revolved then saved, exit of Moi, reenter Moi reopen file and shelled the surface.
See the center of inside render indicating the problem.

During shelling, we think the operation has been ok but in fact, shell has done a curve (on previous picture selected), but didn't use it to construct the internal surface.
It constructs a single surface which is unique, intern and extern.

Hi Phiro, the weird piece that looks like a curve is a surface but with a messed up trimming boundary on it which prevents it from getting a proper shaded display like surfaces normally have. If you select it and use Edit > Show pts you can see the surface control points and if you select its 2 edges and use Delete to untrim it that will recover the surface.

- Michael

Thx for the explanations!
A little more clear now! :)

And no need to make a plane a simple line is sufficient ;)