Maximum distance between curves?

Surprisingly few search results on this, and either Grasshopper results or people saying to use CrvDeviation… but when I try that, I get “Curves do not overlap” and then nothing.

What do people use to get a value on the maximum distance between two curves in 3D space?

got a file?

I mean… any two curves will do?


It’s basically the magenta colored distance I’m after (I just did a linear dimension here, no idea if this is actually the widest part… hence me asking).

I really it’s a super basic question, so I bet I’m missing something obvious. :slight_smile:

well in this specific instance the quadrands indeed mark the maximum distance.

is that so? you are saying that CrvDeviation never works?

having no idea how that command works under the hood, it seems to project normals from and to, and if they dont meat or the focus point is behind the curve this method does not work… no idea if you can call it a bug, it certainly works for some curves.

Bildschirmfoto 2021-09-21 um 15.46.52

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I routinely use CrvDeviation. Occasionally I get the message that the curves don’t intersect but it usually works for me.

Oh, so it’s supposed to work?

Well, I do seem to have a knack for running into bugs the first time I try a new feature… :slight_smile:

Here’s the file with those two curves:

curves-dont-overlap.3dm (137.9 KB)

(Oh, I bet it’s this bloody thing again!)

CrvDeviation does not find the points on a pair of curves which are the greatest distance apart, which in many situations would be points at opposite ends of the curves. Instead it appears to find the pair of “closest” points which are the greatest distance apart. This is sometimes referred to as finding the “maximum minimum”.

The “Curves do not overlap” is not related to the curves being arcs. I rebuilt the curves as non-rational NURBS and the result was the same.

I never have understood why some pairs of curve result in that message. One possibility is it occurs when the closest point on one curve for all points on the other curve is a single point. But that is only a guess.

Use BoundingBox to find for the largest distance parallel to world or Cplane axis.