Hi,
In playing recently with splines, in order to learn about them, I came across the following which I think merits a query.
I drew a random spline using the Interpolate Spline tool. I then drew a straight line intersecting this spline in several places. Using the select tool, I can select the line, or the spline, or any of the points in the spline which are not close to the straight line. Where the point is in proximity to the straight line, I am presented with the (expected) box asking me which entity I wish to select. So far, so good. The problem I see is that the entities offered are "Line nnn" and "B-Spline xxx". When I drew a Control Point Spline and a Bezier Spline, and passed line through each of them, they were correctly identified as CP Spline and Bezier respectively. Should the Interpolate Spline label be altered to read "Interpolate Spline"? I find the "B-Spline" label confusing. I know its only a small thing, but hey, I don't find many bugs!!:D
Regards, Ian.

There's a pretty good page about curve fitting on Wikipedia, here: http://en.wikipedia.org/wiki/Curve_fitting . Gives you the beginnings of an understanding about some of the criteria governing them. CAD programs limit curve definitions as an aid to speed of computation and interchange consistency, whereas Rhino specifically sets out to overcome some of those limitations. Where a degree 8 surface intersects with a degree 4 surface, for example, Rhino could define the intersecting curve exactly, whereas ACIS would fudge the curve within limits. If the limits are below the resolution of your CAM system, for example, there isn't a problem, but if you scaled the curve above it, it would be better to redo the intersection (kind've like picture-scaling interpolation in high- and reduced-definition), whereas it would still be accurate in Rhino. There's an argument for both approaches, but I think they're sort of mutually exclusive.

Speaking of engineering/overengineering, it might be nice to have some Rhino-like action preview to enhance learning from "trial and error" before actually finishing a step.