Offset Loop

MichaelT_123 — Thu, 09 Jan 2025 09:58:32 GMT

Hi FusionFellows, Mr Choppinlt,

Here are my divagations related to the post

https://forums.autodesk.com/t5/fusion-design-validate-document/unable-to-create-a-negative-offset-of-wingtip/td-p/13244326

Offset, regardless of whether 2D or particularly 3D, is quite an expensive procedure and should be avoided unless there are cutthroat or specific circumstances. It is better (and more deterministic) to achieve the goal by explicit modelling.

The operation also has geometrical/topological limitations (T_lim), which a designer can not always sense/envisage.

Here is the example/demonstration of 2D offset and its intricacy. A topology of the curve puts a limit on the allowable offset value, not causing an abrupt morphological change. I manually added the curve marked Manual Addition, which shows the inversion of a topological direction of a curve when the allowable value is exceeded. The new functionality of the F360 offset feature can approximate this limit (Topology Match label).

The situation can be extended to higher dimensions, but drawing related examples would be difficult, if impossible. Thus, as a substitute, imagine a 3D surface passing through singularity (point, segment, infinite line), with normals inverted at the singularity … like Wrigley’s gum bubble surface normals opposite to inner lips normals. It should not be difficult ... in Texas, should it?

How do we ascertain a topological offset limit for a 3D surface? I don’t know the internals of the F360 face offset algorithm, but I think it will be related to the minimal 2D T_lim(s) of the surface 2D projections.

Selecting the likely projections generating T_lim should not be difficult in the case of the wing tip.

Note: The offset term used above can be called a classical offset. I posted some notes about other ‘offset’ types some time ago.

https://forums.autodesk.com/t5/fusion-design-validate-document/csf-curveshorteningflow-mode-shorten/m-p/12277392

Note to the TF360,

How difficult would it be to implement the Topology Match option in 3D face offset feature?

Regards

MichaelT

Re: Offset Loop

kacper.suchomski — Thu, 13 Mar 2025 22:55:22 GMT

The mathematical topological limit of offset geometry is equal to the smallest radius in a given set of surfaces that will be offset inward.
In short, this limit sets the fillet that will first transform into a sharp corner.

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Offset Loop

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