RemoveMultiKnot changes shape during working

[mdesign (Marcin)]

Two separate curves after join into one open curve:

Same curve after triggering RemoveMultiKnot:

Does RemoveMultiKnot change the shape of curves and surfaces? I`ve thought that it removes only those knots which have no influence on the overall shape.

I`ve thought that the curve/surface shape before and after RemoveMultiKnot is the same or almost the same.

Should it work like this?

I`ve read here: http://docs.mcneel.com/rhino/6/help/en-us/index.htm#commands/insertknot.htm#RemoveMultiKnot

that:

The RemoveMultiKnot command removes these stacked knots if they are not fully multiple. Removing the multiple knots can cause some loss in the surface precision, but in practice, this is usually not a problem.

So I thought that those changes are minor. but here you can see that it is a completely different shape of the curve and I’m surprised a bit (maybe because I`m still learning Rhino).

[pascal (Pascal Golay)]

@mdesign

Does RemoveMultiKnot change the shape of curves and surfaces?

Yes - more or less, depending on the input but pretty much always some. How much of a problem it is is up to you, in the specific case you are testing.

-Pascal

[mdesign (Marcin)]

It`s interesting. So in this case I should do RemoveMultiKnot before joining, not after.

[spb (Steven Burzinski)]

@mdesign

I`ve read here: http://docs.mcneel.com/rhino/6/help/en-us/index.htm#commands/insertknot.htm#RemoveMultiKnot

that:

The RemoveMultiKnot command removes these stacked knots if they are not fully multiple. Removing the multiple knots can cause some loss in the surface precision, but in practice, this is usually not a problem.

“If they are not fully multiple” doesn’t apply to curves in V6 and V7. The WIP has an option to reduce the multiplicity of fully knots (in curves and surfaces) less than a settable kink angle.

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