Any method to unify multiple curves?

I wonder if someone could give us an advise about:
How to unify/connect, similar to join but as the final output result in just one curve entity.
The objective is to get one continuous curve so we can extrude it in a surface and this surface became one simple entity.
The final objective is to createUVcrv from that surface so we can Flowalongsurface.

Sorry our english.
Thanks for any advise. / Cheers

Generally Rebuild will create one single NURBS curve. Depending on the input and the Rebuild parameters, it may change the original shape. Any sharp kinks will be eliminated.

Thanks for your quickly reply.
But rebuild doesnt give me the same exactly curve. It result in a near identical but no the same. «seldup» command confirm that.
Any other suggestion?

In any case SelDup will not consider a rebuilt curve the same as the original, as its geometric definition is different - SelDup does not look for something “close”, it looks for something “identical”. You can try this with a line, make a copy of it in place, rebuild the copy to degree 3 and 4 points, then try SelDup. It won’t select, but the rebuilt line is still for all intents and purposes the same line.

The point I was trying to make is that if you have a polycurve that you want to make into one single curve, Rebuild is one way to do this. You need to check the difference between the original and the rebuilt curve with CurveDeviation to see if it’s within acceptable tolerance. More points on Rebuild will generally get you closer, but the curve will be more noisy and harder to edit.

You can also try FitCrv and give it a fitting tolerance, make sure the AngleTolerance setting is very small though otherwise you may not eliminate all the kinks in the curve.

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Ok. Understand.
I will try to do it that way.

Also, if your single curves are curvature continuous to each other, joining those before extruding will create a single surface. When you have single curves that are only tangent continuous to each other, you can turn off the SplitAtTangents option in the ExtrudeCrv command to make that produce a single surface.

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Rebuild does not create a single curve from two curves for me. What am I missing?
Edit: Rebuild creates a single curve from a polycurve but not separate curves. Good to know.

Match with the Curvature continuity and Merge options will create a single curve from two.

I think i have to exemplify with a file or a printscreen…

Yep, that’s what I meant, I assumed they were already joined into a polycurve.

Yes, but if there is a kink or non-curvature continuous joint, it will modify the curve…

Sorry the delay. We are on a dead line here at office.
Curve_testing.3dm (10.4 MB)

You have 3 degree 2 curves which have position continuity.

Extrude each curve by itself to the same height.

MergeSrf with Smooth=No will result in a single surface with kinks.