Sweep2 Strangeness

Why do the results of Sweep2 frequently have discontinuities in curvature (multiknots) when the input rails and sections are smooth? My expectation is smooth input should result in smooth output.

Example: Sweep2ExampleA.3dm (77.7 KB)
Rails are single span, 4 control point degree 3 curves.
3 sections are straight lines.
Result is a 39 x 2 control point surface with multiknots at 9 locations.

I’ve always been confused why it does that by default. It seems counterintuitive to have to check the Simple sweep option to get the correct result.

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Hi All -if the section curves do not fall on matching pairs of edit points, as in EditPtOn, and the rails do not match, then a simple sweep is not possible and the rails are refit. In some cases it may pay to first RemoveMultiKnot on Sweep2 output, then MakeUniform, but it won’t be ‘simple’.


Why the multi-knots from “refitting” smooth curves? It seems to me the algorithm could be improved.

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In the example above the pop-up window has a box for selecting “Refit rails” which could be interpreted as meaning that if the box is not checked the rails are not refitted. But that is not what happens - the rails refitted independent of whether the box is checked or not.

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