Tangent vector at the point of curved-folding question

I was reading this paper and trying to do curved-folding by Kangaroo
One-DOF Rigid Foldable Structures from Space Curves (2).pdf (1.6 MB)

The first obstacle is that find normal vector on cuved folding .
Does any one know how I can find the normal verctor like this picture??

This is what I done so far.

ruling lin_ curved folding.gh (8.2 KB)

@jack3661mao, you need to internalize your data before uploading the GH file, otherwise the geometry won’t be available for other people!

That said, you can usually get the normal vector at a curve parameter by calculating the cross product between the tangent vector at the parameter and for instance the world z-axis.


Another, more method would be to use the Perp Frames (PFrames) component, which also takes into account the curvature.


If a given Brep edge is the folding edge, then (for tol to t-tol) get the tangents at t - tol, t + tol (tol: a user defined value, maybe the doc tol maybe not) and their CrossProduct.

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what does this mean??

I finally can solve.
Thank you so much.

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