Object won't split

Happy Thanksgiving! I have a project I am working on and I can’t get the objects to split. I think it has something to do with the fact that I had to match the surfaces of the topography and then join them to make one. It looks like one surface but perhaps is not acting like a single surface? Any advice would be much appreciated. Thanks! split issue.3dm (9.2 MB)

rebuild the surface of the zylinder like i did, intersection, trimming and splitting then takes place. you can also try a lower amount in the V direction till it works maybe even 3. thats actually the only thing which yo have to change. you can keep degree and the point count of the U direction. just give it a few seconds to computer when trimming/splitting.

Hi Courtney - two things -

  • Tolrances are too large, set this to .001 in document properties. See
    https://wiki.mcneel.com/rhino/booleanfaq for more info.

  • Rhino still fails to find an intersection (Intersect command) - this is Rhino’s fault, and you can often as in this case get it working by adding some density to sparse surfaces - the cylinder in this case. Use InsertKnot, in the vertical (V in this case) and hit Automatic two or three times, Unlike Rebuild, this will not compromise the shape of the cylinder in any way. Intersect the two to verify that you have a good curve of intersection. With tolerance at .01, this is an open curve, not useful, but at .001 it closes up and you can trim both surfaces with it.
    Any luck?


Worked! thanks RichardZ! I tried rebuilding the other surface but I didn’t
think to rebuild the cylinder!
Thanks again!

Courtney Reckord
Artist, creativity coach

Thanks Pascal! I will check out the tolerances!

Courtney Reckord
Artist, creativity coach

Hi @pascal,
I haven’t had any trouble with splitting up to now, but for some reason this model is giving me trouble.
I tried intersecting the two surfaces, and while rhino says ‘found one intersection’ I don’t know how to actually see that and know if it’s a closed curve or not.
I tried rebuilding, and I checked tolerances- they are
angle: 1
If you can think of anything I am doing that is causing this problem, I would appreciate it,
Here is the link to the file.

Hi Courtney - see how this works - make the profile for the roundy shape as a closed curve

then Revolve it as ‘Deformable=Yes’ and set maybe 32 points for the deformable revolve. That should split as expected.


Thanks so much @pascal!

@pascal, I am so sorry to bother you again.I am trying this and again having trouble. I have inserted knots, checked the tolerances and my piece just won’t split. I don’t know how you create the profile- seems like a really really dumb question so I am sorry. I hope I don’t have to ask you about this again and I appreciate your help so far.

Hi Courtney - I am happy to help but it is pointless just telling us you have a modeling problem if you don’t post a file with the objects…


Thank you @pascal yes I realized that immediately after and am working on that now. It’s too large to upload so I am uploading to my drive and then I will share a link.

Here is the link. Sorry for being such a nincompoop @pascal

Hi Courtney… somehow, you have a surface in there that, by itself, has 1800 by 1800, = 3,240,000 control points… A hundred is kind of a lot…
Still poking…

That surface is completely intractable - the rectangular landscapey one - Refitting it (FitSrf) takes for ever and fails to do anything at a small tolerance, trying again at a higher one. But, meantime - are the details on this really going to survive any manufacturing or fabrication process? What is the overall scale here? (I’d measure but refitting is under way and may take 20 minutes…)

So, @cwreckord - your relief panel is .24 mm tall overall. How will it be made?


Hi @pascal this is a topo map- and will be made tiny so I definitely don’t need all of those points. I get the surface from usgs via the elk plugin. I am sure there is a way to build the surface without getting all of those points but I do not know how or how to to simplify it afterwards. Usually I made jewelry with a smaller area but this is for a woman who wants a larger area - including her hometown. If you have any suggestions for me I would appreciate it! Thanks again!