Adjust the shape of a spline, keeping length constant

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Adjust the shape of a spline, keeping length constant

Postby splainer » Fri Jan 24, 2014 6:17 am

I am looking for a way to take a spline of a specific length, and adjust its shape without adjusting the length. For context, this is for apparel patternmaking, where you have a roundish armhole shape into which you need to fit the top (cap) of a sleeve, which generally has a bell-like shape. The length of the armhole determines the length of the sleeve cap.

I can draw the cap shape and determine its length, but haven't figured out a way to set its length and keep it constant while I fiddle with the curves. Is there a way to do this?
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Re: Adjust the shape of a spline, keeping length constant

Postby andrew » Fri Jan 24, 2014 11:49 am

There is no way to constrain splines like this in QCAD.

Here are a couple of suggestions:
- Keep an eye on the length property of the spline in the property editor while editing the spline
Or
- Split up the spline into smaller segments. Instead of modifying the spline segments, only move them around or rotate them, thereby guaranteeing that the total length stays the same.
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