CV Spline Implementation Details

[bpoweski]

I'm in the process of generating CV splines for a model outside of fusion and would like to know some of the details on how they're implemented so that I may unify the calculations. 

Effectively, I'm looking for something similar to what is discussed here http://www.theprovingground.org/2012/09/interoperable-geometry-part-1-curves.html.

1.  Does Fusion 360 follow the sample implementation choices as Revit?

2.  How does Fusion 360 choose the knot spacing i.e. are they uniform?

[jiang_peng · Accepted solution]

Thanks for using Fusion360!

1. Yes we are following the sample of Revit
2. Yes the knot spacing is uniform.

For example, a degree 3 and 7 control points spline, the knot vector is (0, 0, 0, 0, 0.25, 0.5, 0.75, 1, 1, 1, 1). Please note some operations will manipulate the knot vector, such as Trim/Break/Insert control point/Remove control point. The knot vector is no longer uniform after the operations.

thanks

[bpoweski]

Thank you!

I’ve been using scipy differential evolution to fit CV splines to sketch points in order to create smooth fair curves.  After a bit of fine tuning it’s working out quite nicely.

Once CV splines are in the API (last I checked they were not) it should make for a useful extension.