This brief (2:47) video illustrates how to draw and edit a spiral interactively and provides information on the optional parameters:
This tool draws a smooth curve that passes through a given set of points. For example, the Cornu spline on the left in the figure below passes through the endpoints of the line segments shown on the right.
You can use an
existing line as the basis for creating a Cornu spline or you can draw
a Cornu spline interactively. You can also interactively edit a Cornu
This capability is an adaptation of path.py created by Raph Levien (http://levien.com/spiro/) with insights from Cornu for Nodebox (http://nodebox.net/code/index.php/Cornu). Thanks to Raph and to the Nodebox team for their expertise, creativity and generosity.
At the 1:50 mark of this brief (3 min) video, there is a demo of interactive drawing and editing using the Cornu spline tool: