Mesh Offset results are not uniform

I’m trying to offset a mesh by a uniform value. The attached .STL works for the most part, but it appears the dome section doesn’t offset correctly,creating an overhang. I was curious if anyone had any insight to why.

I have tried using Weavebirds Meshoffset as well at the Rhino Meshoffset command via python and the both yield the same results. If scale the mesh, the result is correct.

I’m looking to achieve the same result using offsets and not having to do math to generate a scaleNU factor later down the road on other shapes.


CalibrationPiece2.STL (220.8 KB) (7.6 KB)

Polysurface and mesh cubes of 1x1x1mm, offset of 1mm;

Mesh offset is not per-face but per-vertex.
On a brep/polysurface the offest make the offset of every face and then it fix the edges.
On a mesh the offset is done by just moving the vertexes by the average local normal x offset value.

You could get a bit better result if you increase the face count of your mesh, so a big flat face have many new vertexes inside that will be moved (by offset) correctly; corners will still be ugly though.

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Thanks for the insight. This clears things up and with that I’ll be able to make the proper adjustments.

try this

mesh (17.2 KB)