Revit/Vasari has a couple kinds of splines, regular spline (A) and spline-by-points (B). You’d think they were pretty similar, but you’d be wrong. I’d like to show an alternative to these 2 curve types, (C), a point hosted control polygon based curve.
Regular Spline, sometimes called a b-spline, has a control polygon and a weighted “attraction” to the placement points while Spline-by-points passes precisely through it’s placement points. Perhaps more important, the Spline-by-points is much easier to associate with other geometry, flexing and stretching with it’s host in a way that is not possible with the regular spline tool, and it is also a 3 dimensional curve that is not restricted to one plane.
So what can you do if you want the weighted polygon behavior but want to keep the associations between the curve and a host?