Cubic spline interpolation

[mrandreev]

cubicInterpolationMode has only two modes for interpolations:

• default (custom weighted cubic interpolation)
• monotone (monotone cubic interpolation)

We need cubic spline interpolation and as I understand from source code its not the same, isn't? If so is there any approach how to provide custom interpolation mode or some workaround?

Thanks!

[etimberg]

@mrandreev unfortunately the only way to add this would be to modify the code. I'm not exactly sure what the math for cubic spline interpolation is otherwise I could try an implementation. Do you have any documentation on how this might work in a chart?

[mrandreev]

hey @etimberg, thanks it will be really helpful!

I had some research on 'cubic spline interpolation' method so if shortly:

• math definition
• CSPL.js lib
• cubic-spline lib

Actually its popular method for smooth interpolation and already implemented by community (I hope it will be easy to integrate).

Also could you please clarify about the "default" mode. As I see from source code the default method is similar to Bezier curve (but not sure). Just want to make sure its not the same one (to cubic spline) but with diff approach.

Thanks!

[etimberg]

Thanks @mrandreev. The default is a Bezier curve with a tension of 0.1.

[mrandreev]

@etimberg I would like to clarify is there any possibility to support 'cubic spline interpolation' mode in near future? It will be really useful mode. Thanks!

[kurkle]

I think, that Bézier is a cubic spline curve. Another cubic spline curve is b-spline. b-spline can be drawn using Bézier, so that would be possible to implement (as the canvas only supports Bézier).

See: https://www.maissan.net/articles/simulating-vines/2

I'm not sure if b-spline is something that is requested here though.