Cyma Curves

I just wanted to pin this thought somewhere. I do a lot of work in classical styles, and as a result I’m always dealing with cyma curves. I generally try to consult historic literature for techniques in drafting, which results in me attempting to decipher highly ambiguous line work. From everything I have read, two principle ways to drafting cyma curves reappear:

Both produce pleasing curves, but I am interested if anyone has a preference of the two (maybe someone with a mathematical basis), or even an alternative?

Initially A and B seem to produce very similar curves:

When the pitch is more extreme the differences between the two becomes more apparent:

One way I do it is like this:

That’s neat. I assume the ability to set the chord proportion means it generating a truly continuous curve and not just splicing two arcs together. I will definitely give that a try.

Dave, what’s the name of the extension you’re using?

Cyma Curve Tool by TIG from Sketchucation.



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So glad I read this! Another plugin that I didn’t know I wanted but am so getting! Actually got stuck with this problem myself more then once!

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I’m wondering if the segmentation of the circles has something to do with the different outcomes…

Nah its equal segments. The two methods create different arc centres and so the curve is different

They can be the same…
Cyma curve.skp (1,4 MB)