Offset problems

Hi I am relitavely new to Rhino so some help would be really appreciated.

I have uploaded my file if that helps.

I am trying to give this shape walls so am joining the 4 surfaces and the offsetting them by 25mm but on doing so one of the surfaces is splitting from the other.

This file is my start point so if I join srf. then offset by 25mm you will see the inner curve sort of separates, can anyone help?



3.Second section complete…3dm (3.6 MB)

I am now trying to connectsrf but it doesn’t work either, shows lines where the connection might be made so I click done and they vanish with no connection made.

Hi Simon - use the Solid=Yes option in OffSetSrf for this, or Cap first and use Shell, selecting the caps as the faces to remove. The ends are a little cleaner with the latter approach.


I have tried that Pascal, I want to add 25mm so can’t use shell, the solid option just produces the same results but a solid version, ie the inner curve detaches itself.

Ah - going outward.That is messy - the the surfaces must be extended to make that work and the side surfaces do not extend in the direction you’s like, see how in wireframe the isocurves are skewed? so the extension will not happen in that direction and some of it misses or barely hits the extension of the middle surface. If you made this with Sweep2, try the AddSlash function to true up the side isocurves to be more radial and not so skewed. Post the inputs if you like.


I will try that Pascal, many thanks. Not used addslash before but will try and get to grips with that and post back.

Had a couple of goes at making the sides more radial but getting the same results.

Hi Simon - see the attached, offset the one on the right. But. I’d build the outside 25 units larger and Shell the capped object - the ends will come out cleaner and the outer surfaces will be the visible ones as built, so to speak, which is good since offsetting can reduce the coninuity and increase the complexity - assuming of course that the outer surface is the one that counts …

Second section complete_PG.3dm (3.8 MB)


a little more work but you dont have to rebuild your initial curves, you can offset the cross section curves by 25 just join them and offset and explode them again. then use sweep2 with both rails you already have and both corresponding cross sections on all sides.

Second section complete…3dm (6.2 MB)

Thanks Pascal, really appreciate your help, I think I will do as you suggest and re-draw with the additional 25mm added then shell it.

This component is only the middle part of the form so will adopt the same policy for the entire thing…

Richard, just seen your reply will look into it, thanks.