How to create an "edge" all around a solid (a section) and then scale it down?


let’s say I have this solid:

and want to make this:

At the moment, I manage do this by splitting the solid with a plane, join them with BooleanUnion and finally scale down the section with the gumball.

But, I would like to know if there is a better, easier way to do it ? The “Section” and “SplitFace” almost do what I want, but the Section doesn’t create a controllable “edge” , juste a curve; and SplitFace does what I want but only on one face.

I’m still pretty new to rhino and I may be overlooking something pretty obvious.

Thank you for taking the time to read this post. :slight_smile:

I think you’re on the right track. I’d suggest using Section to make the curves defining the split locations. Then immediately Group them if there’s more than one with ctrl+G. Then Split using that group of section curves as the cutting objects. Use J+Enter to Join the resulting selected pieces after the Split and then scale sub-object selections with the Gumball using ctrl+shift to select the edges or faces.

In the v6 WIP there is a new ‘infinite plane’ option too that you could use when splitting by typing “ip” when asked for the cutting object. This will save the step of using Section… and would make for a nice aliased workflow too e.g. “Split IP V pause pause enter Join”

Options>Aliases lets you string together commands to be run together with an Alias.

Just for fun, here’s that Alias at work in the v6 WIP

Thanks a lot Brian !
I didn’t realise that you were able to split with the section
I will try the v6 WIP when I finally buy my Rhino licence, you also taught about stringing aliases and I manage to create an alias that automate a part of the process, on the v5.

“!_Section pause pause pause pause pause _Selnone _Split pause pause _enter _join”
(I may have put to many pauses but well, it works)

Yours seem what I really , I will wait a bit.

Hi Vermona - You might also, in this context, want to ShrinkTrimmedSrf after the splitting.


Here is another quickie method:

  1. Draw a line where you want to split the object
  2. Use Split to split the object in the Top viewport
  3. You can delete the line afterward
  4. Use Join to join the two split parts back again (the internal split edge remains)
  5. Use Ctrl+Shift+Window to sub-object select the split edges
  6. Move or scale the edges as you like - with Gumball or any normal Rhino command like Scale.