Ah hehe gotcha, I missed you’re author, and you were saying CatRom and B-splines have similar locality. I feel like talking about local control’s a bit iffy. In a spline with multiple cubic segments, I think a control point edit is going to affect about the same span of arc length with all three bases Bézier, CatRom, and B-spline, no?
My claim that the Curvature Bézier has less locality, of course, was based only on editing one of the Bézier’s shared join points. When you edit a shared point’s position (by moving an anchor) or tangent (by moving either of the interior control points), you are affecting 2 segments, not just one, hence the 7 control point span. I’m being a bit sloppy but I’m sure you understand what I mean there - the portion of curve affected by a single control point edit technically affects a section of the curve that’s fully determined by exactly 7 consecutive control points. (Assuming cubic!)
Re-thinking B-spline, I believe I goofed - editing a control point affect 4 consecutive curve segments, which is the non-locality you’re referring to, but which is also a span of 7 control points, so very similar to editing one of the constrained Bézier’s shared anchor points. The window of which 7 control points slides smoothly with B-spline: the edited control point is the middle of the 7 control point span. With a curvature-constrained Bézier, each shared anchor and its two surrounding control points affect the curve defined by the same 7 control points.
So yes cubic Bézier segments that aren’t constrained in any way (i.e., the “cusp” and “corner” types), sure those have a kind of ‘locality’ in that editing the two interior control points affects only the 1 segment defined by 4 control points. But as soon as you add constraints on the tangents, neighboring segments affect each other, and your control naturally becomes less ‘local’, right?
So anyway, given that adding constraints to Bézier splines will cause neighbors to affect each other and control point edits are no longer confined to a single segment, are there other reasons to stick with Bézier?