Workflow Improvement Advice: Separate Inner and Outer Shell

Hi. I am attempting to machine a mold from this closed polysurface. I wanted to booleanunion this object from a block but cant figure how to make that work. What I ended up doing was deleting the facets attaching the top shell to the bottom shell and working from there.

Is there a simple way to separate that top shell from the bottom?
A faster workflow all together? I am a little rusty so any advice is greatly appreciated,

Hello- you can try this plug-in - if you set a high angle tolerance - maybe 45- 60 degrees or so, and pick a face on the front or back as a starting face, it should find all the faces on that side.

ExtractTangentFaces.rhp (40.5 KB)
You’ll need to unblock the rhp in Windows and then drag and drop it onto Rhino. I think this one is compiled for V7 +, not sure if it will run in V6. The command is ExtractTangentFaces.


Hey! Big fan of your work! Thanks for the speedy reply. I am using R7:

Resulting Command History:
Version of Rhino the plug-in was built for
does not match the this version of Rhino.
RhinoCommon SDK Version = 5.1.30000.17
Plug-In built for version = 6.0.18016.23451
Unable to load plug-in C:\Users\kevin\Downloads\ExtractTangentFaces.rhp

Well, hat is odd - that is the same one I am running here on V7.

But I am not sure what this means:

“RhinoCommon SDK Version = 5.1.30000.17”

Does Rhino think you have a V5 SDK? Have you bay any chance installed or reinstalled V5 after installing 7?

Meantime, until I sort out what is going on with the rhp, here is a Python version of the same thing - (25.6 KB)

You can run that by

_-RunPythonScript "Full path to py file inside double-quotes"

It is a messy and convoluted script, from years ago, but I think it works.



1 Like

And to answer the Rhino 5 or 7 mystery…I just upgraded from teaching license on Rhino 5 to commercial license on Rhino 7. Should I take action?

No, I don’t think so, yet, anyway… it just seems weird to me that the plug-in does not work on your V 7 but you get a message about the V5 sdk…

Let me run the compile again from V7- hold on a bit.

@kcook01 - see if this one works - I compiled it from V7.5.

ExtractTangentFaces.rhp (41 KB)


Oops! It was useful to delete the copy of Rhino 5 competing with Rhino 7. Too much Rhino energy. Everything is working great now.

I used to teach Rhino and whenever I would get stumped I would search and then see your name at the bottom of a very good answer. Thanks again for your help over the years!