Help needed with finding centre line through 2 curves

Refit in TweenCurves uses “RhinoMakeCompatibleNurbs”, which is similar to what commands like “Loft” use to refit. TweenCurves refits within 0.01 tolerance. This is different from FitCrv which uses “RhinoFitCurve”

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What about this one? (It was missing one point, so I had to shift the list, but apart from that, going from Frame -> Vector X (reverse) -> Line, eval 0.5, and line between these mid points, and there it is?

Tweening Curves 02.gh (8.0 KB)

This is “tangent-perpendicular”.

// Rolf

Yes, this can work.

that looks like what i am after, hard to explain but the lines from the centre line i am trying to find need to be perp. to it, and those lines look to be travelling in the right direction. I am no expert so am affraid your explanation of how you did the flew several feet over my head :)…only have rhino btw

Better picture (showing also the tangent vectors)

// Rolf

Picture with explanations (plus latest GH def)

Tweening Curves 03.gh (12.5 KB)

OK, so I upload the resulting Rhino file. You can manually clean away the points and helper lines. I didn’t touch your lines, so you should be able to use them.

Tweening Curves - Experimental drawing RE.3dm (126.1 KB)

// Rolf

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See attached file. All distances are equal using the algorithm.
Experimental drawing_RI.3dm (3.3 MB)

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Was thinking similar after your comment.

simonms check that rhino. Is that the midcurve you are looking for?

TanTween.gh (7.4 KB)
TanTween.3dm (79.0 KB)

One question. Why didn’t you turned on reparametrise option in evaluate curve component?

Experimental drawing_Akche.3dm (105.0 KB)

After making end of outer curve perpendicular to inner, I get this.

Method for mid-curve which is locus of points which are equal distances from the side curves. This definition is independent of curve parameterization, and of relative position of curve ends.

  • Create set of circles which are tangent to both side curves. (Spacing of circles is not critical.)
  • Find center point of each circle
  • CurveThroughPt through center points. (Chord may give smoother result than Uniform.) Alternative would be InterpCrv.

Attached example was done manually in Rhino. Should be possible to “automate” using Grasshopper. DC_Mid01.3dm (118.5 KB)

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here you go! Experimental drawing_David_option.3dm (111.5 KB)
David_option.gh (10.6 KB)

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Thanks for all the replies here, i will plough through it this morning. I am not an expert on Rhino so fingers crossed.

Maybe this screen shot will explain a little further what I am trying to achieve, i have drawn in some red lines to show the beginning and end of the form i am trying to create, i have the inner and outer curves so just need to establish mid line and segments as per the attachment.

Hmm, there are three circles here intersecting the inner curve at tangent, at equal interval to inner curve and then outer one. but it’s confusing how many tangents each circle have. What if this to be made in golden ratio? That would be more appropriate or precise. I can try to do this way but not now.

Yes, the drawing is an example of how this was done in the past I guess so just see it as a general guide to what I am trying to achieve, what I am after is a mid line divided into 10mm spaces with the lines plotted in, each with equal distances above and below mid line conforming to the type of layout shown here.

I think I have managed to get the outer curves quite smooth by extending to perp. at each end.

Again, really appreciate the help.

In your case, for each curve, I see one two circular arc joined together at tangent to form this curve. Can you manage to rationalize or optimize it into two circular arcs for each curve? That will make your curve graph even.

Ok! I was talking about golden ratio. This is how it worked. I hope that it is close to what you need. Curves.3dm (532.9 KB)
David_option.gh (14.0 KB)

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