Issues working with a Closed Solid Polysurface

Hi All,

I can’t seem to do anything with this closed part. I’ve tried the following

  • Trim
  • Split
  • Boolean Difference
    Nothing seems to work… I’m probably overlooking something very simple, but just wanted to make sure it’s not a bug.

Problem Part.3dm (2.7 MB)

Hi @basilp
I can’t tell you why this isn’t flagged as a bad object, but it should be. Try running DivideAlongCreases with SplitAtTangents=Yes. There’s at least one bad surface on each side - and besides that the whole thing is a bit of a mess with lots of long, thing slivers and weird trims. Was this made in Rhino or imported? If made in Rhino, it’s probably a good idea to try and re-model the whole thing with cleaner curves; depending in the end-target, of course.
Edit: If you extract the cross section in the middle there’s a lot of continuity issues - curves that are almost, but not quite, tangent, overly complicated curves etc.

Thanks Jakob - it was modeled in Rhino. I guess where things may have gone bad was when I exported a STEP to preform rounding operations in Plasicity, then re-imported it.

Hi @basilp
Ah, yes - that might be it. I’m not familar with how Plasticity handles all those fillets, but since the surfaces come in as large panels, I’m guessing it’s jumping through some hoops to get there :grimacing: I’m wondering if Plasticity - which I believe is based on the Parasolid kernel - can be forced to split all those fillets into actual surfaces instead of a single combined surface (I can’t remember what that type of surface is called… Hopefully one of the bigger NURBS-brains will chime in). If you extract just one of the large front surfaces and DivideAlongCreases there’s at least one long sliver with an area of just 0.03mm, but it’s a trimmed version of the full fillet - not exactly optimal geometry.


I think I found the problem. Note the shallow circular counterbores on the backside of the part. When I generated those features with the boolean difference command it seems to have created the issue. Once I boolean the part with these cylinders it causes the problem. I re-imported the Plasticity part without the backside booleans that were done in Rhino and the part cut fine. As it turns out the rounding in Plasticity wasn’t the problem.

Problem Part_2.3dm (2.8 MB)

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topic solved ?

@basilp - the part does not go bad here if I BooleanDifference the cylinders from the larger part - is that what you meant/ ( some do not fully intersect all the way around the cylinder btw, but the Boolean seems fine here)


@pascal - I’ve tried to dissect the extruded part and appear to have issues the geometry. I initially thought it was isolated to the graphics, but the problem showed up with my 3D printed parts. Here’s an example of the backside of the profile swept along a single degree curve. Note that the profile is not accurately tracked. I’ve also attached the file (Rhino 8 - Win). Thanks
Profile Issue_1.3dm (92.8 KB)

Hi Tom - Problem was not solved, it appears there’s a lot more going on with this extruded shape than what I initially observed… Thanks

Hello- please try DivideAlongCreases > SplitAtTangents = Yes - that shoould clean up.


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Thanks for the “DivideAlongCreases” command advice @pascal further backed your claim and you are both correct. Certainly appreciate the assistance.