A Demonstration of the Hobby Algorithm
 
This should work with recent desktop versions of Chrome or Firefox. It was coded using Vanilla JS.
 
The left half shows natural cubic splines, the right half shows the Hobby algorithm. (Click on the links for videos about these topics.) Click somewhere in the graph to add a point. You can also use the mouse to move existing points. Press the Backspace key to remove the last point and press r to remove all points. Press c to toggle between open and closed curves. Press h to toggle between showing both graphs and showing only the left half. Press a digit to add a point on the graph after the n-th point. Press 0 to revoke the last digit. Press w to switch between the "curl" values 0 and 1 for endpoints in open Hobby curves.
 

 
Copyright (c) 2018, Prof. Dr. Edmund Weitz. Impressum, Datenschutzerklärung.