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What is a "spline" ?

Posted: Fri Jun 21, 2024 9:24 pm
by thornuk
I'm not sure how QCad is using the term "spline".
I'm used to it referring to (eg:) a grooved circumference of a shaft onto which a similarly grooved hole in a cog or gear wheel (to lock the two together for drive purposes.
Thanks
PeterB

QCad version: 3.28.1.0 (3.28.1)
Windows 10

Re: What is a "spline" ?

Posted: Fri Jun 21, 2024 9:29 pm
by andrew
In QCAD / CAD / mathematics, a spline is a type of curve:
https://en.wikipedia.org/wiki/Spline_(mathematics)

Re: What is a "spline" ?

Posted: Fri Jun 21, 2024 10:26 pm
by thornuk
Thanks, Andrew,
Would that be an equivalent to a Bezier Curve ?

Re: What is a "spline" ?

Posted: Sat Jun 22, 2024 6:24 am
by CVH
thornuk wrote:
Fri Jun 21, 2024 10:26 pm
Would that be an equivalent to a Bezier Curve ?
About, not really, I think that the supported types are B-Splines aka Non-uniform rational Basis-spline (NURBS).
In the wiki link by Andrew see 'Representations and names'
Also see: https://www.qcad.org/rsforum/viewtopic. ... 8665#p8665
On the Bézier curve there is another wiki: https://en.wikipedia.org/wiki/B%C3%A9zier_curve
And on NURBS: https://en.wikipedia.org/wiki/Non-unifo ... l_B-spline

A cubic Bézier curve has for example 4 control points, a cubic control point spline has at least 4 control points in QCAD.

One can convert the splines to Bézier segments, see: Misc .. Modify .. Convert Splines to Bézier Segments.
Not native but besides control and fitpoint splines QCAD support something that looks like a chain of Bézier Segments.

Regards,
CVH

Re: What is a "spline" ?

Posted: Thu Jul 18, 2024 10:27 pm
by thornuk
Many thanks CVM.