Convert flat spiral to helix

Is it possible to convert a flat spiral to a helix while the edges of the spiral are intersecting at some points? Is there any easy workflow for it? Here is an example attached.
spiral to helix.skp (84.5 КБ)


Redraw the path with a spline, then use FredoTools > Curvishear


Excellent! Thanks)

just tried to do it but in my case fredo spline makes a spiral made of edges but not as a single curve that’s why curvishear doesn’t work as expected. What can be a reason for it?

Here is a simple short example

Try uncheck “Generate in”, and don’t activate “Plane Z”

spiral to helix - SU2020.skp (122.5 KB)
I tried again and it works ok

If you are drawing over the existing 2D path, don’t forget to group it first.

hmm, don’t know why that doesn’t work for me…

I’m using the latest versions of Fredo tools, spline, etc. SketchUp Pro 20.2.172

Maybe in your case there is no intersections indeed

So, If I move a little bit of the plane it will work as curve

All we have to do is ask @Fredo6 nicely to help us understand why this is happening and sometimes the spline is formed, other times not (it breaks).

In Sketchup, you cannot have a self-intersecting curve. Sketchup automatically split it in several curve portions.

However, when you generate the curve from the API (add_curve method), even self-intersecting, it seems that Sketchup does not realize that there are intersections (except if at a vertex) and keeps the drawing as a single curve. This is an accident I guess…

Thank you for the explanation, Fredo! Because it worked for me right from the start (and knowing about Eneroth’s plugin), I thought that the created curve has the property of not breaking when it meets another edge.

Using the Eneroth Edge Breaking Toggle plugin and FredoSpline allows the creation of an self-intersecting curve without breaking/split

Or in this particular case, Yuri, you can even replace some of the edges already drawn and then join them so you can use Fredo CurviShear

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I don’t have an explanation, except that the API may have a different behavior than the function Weld Edges in the UI.

Also, it is possible to have curves crossing other edges, when the curve is in plain (not soft, not smooth) and crosses edges which are soft.

In fact, to solve the issue, I should make CurviShear accept a sequence of edges, rather than a true Sketchup curve. Just a matter of coding, I was probably lazy at that time.

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