Offset object solid - pain

In the attached… the “client” wants to offset the simple polysurface object to the outside 0.1 units, solid.

  • OffsetSrf with rounded corners succeeds, but the client wants sharp corners.
  • OffsetSrf with sharp corners explodes and leaves gaps

OK, let’s try the OffsetMesh route…

  • Mesh the object… Unable to get all simple 1 triangle faces, they are arbitrarily split
  • OffsetMesh the result does not offset correctly anyway (fold added, thickness not constant)
  • Fix the original mesh by manually deleting/adding faces
  • OffsetMesh works
  • MeshToNURB… Done…

But geez… a lot of work for a simple object and lots of failures…
So for "bug reports, I would like to file the OffsetSrf (sharp) failure, the Mesh failure (can you find a mesh setting that will make all single triangles?) and the OffsetMesh failure.
Thx, --Mitch


Mitch, you can get triangles from the faces if they are trimmed planes. I don’t say the singular faces should not as well, but just fyi, for now. Offsetting the mesh then works nicely. Checking on the rest…

Looks like offsetting also works way better when the planes are trimmed- Chuck says he’ll see about making planar surfaces trimmed planes for the purposes of shelling, regardless of their structure.


OK, that’s good to know, I have a script that will replace untrimmed planar surfaces in a polysurface with trimmed planes. However, OffsetSrf sharp still fails afterward, but yes, the mesh and its offset are much better, thanks.

OffsetSrf worked perfectly on the trimmed faces version while Chuck was looking over my shoulder. No longer though… now it works - makes a solid (at .001), but does a weird thing in deciding on the corners. Still checking.


OK, I get his at 0.1…

Yeah- at .001, the same but closed. If I true up the top plane to be parallel to the bottom, I get a closed object at .01. Another solution would be to chop off the points and make the outer faces four edged, which is what my solid modeler gives me…


Hi Pascal and @chuck
Would it not be better practice to ‘convert’ planar surfaces to trimmed planes at the start of an offset procedure? And leave the input geometry as is. In any case, would it not be so that imported geometry that is a planar surface will still cause offsetting to fail? Maybe I misinterpreted the suggestion, but should the command not itself take care of preparing geometry for best results, instead of relying on the quality of input geometry?


Hi Willem,

Yes, that’s the plan.


Hi Willem- I don’t think any of the user’s existing geometry would be affected, just how the offsets are worked out- if Chuck uses a plane rather than a singular (or whatever) surface to work from internally, things like extending the surface do not cause any problems. I imagine any new offset planar surfaces would also be added as trimmed planes and not reflect the input structure, if I understand things. But I just made that up.