Decompose Bspline

[ajayre]

Hi, I have a Bezier curve of degree five

BSpline Spline = new BSpline((uint)_ControlPoints.Count / 2, 2, (uint)_Order - 1, BSplineType.CLAMPED);
Spline.ControlPoints = _ControlPoints;
Spline.Knots = _KnotVectors;
BSpline Beziers = Spline.ToBeziers();
...
if (Beziers.Degree == 5)
{
  ...

I need to break this up into Bezier curves of degree three or less. What do I need to call? Note that I am using the C# bindings generated by swig (which I don't really understand).

I see there is ts_bspline_to_beziers and this appears in the namespace TinySpline.tinysplinecsharp but how do I call it? Is there an example? Is it even the right function?

Thanks, Andy

[msteinbeck]

Hi @ajayre,

Hi, I have a Bezier curve of degree five [...] I need to break this up into Bezier curves of degree three or less.

You cannot reduce the degree of a spline with ToBeziers(). ToBeziers() simply "cuts" the spline into a sequence of connected Bezier curves where each Bezier curve has the same degree as the spline on which ToBeziers() was called. Degree reduction is not (yet) implemented in TinySpline. I did some research in the past and found the following paper: https://www.academia.edu/78438328/Degree_reduction_of_B%C3%A9zier_curves Section 2.1. presents an approach how to reduce the degree of a spline. Note, however, that the shape of a spline slightly changes when reducing its degree.

[ajayre]

Thanks for the pointer.

[msteinbeck]

I'm closing this issue. Don't hesitate to reopen it.