On Fri, 2005-04-01 at 20:07 +0100, [EMAIL PROTECTED] wrote: <snip>
> I still have some, from the 1950s ... The curves in the edges > are supposed to be segments of logarithmic spirals (which > ensures a kind of self-similarity on different scales). > A nice picture is at > > http://missourifamilies.org/learningopps/ > learnmaterial/tools/frenchcurves.htm > > Splines, in the drawing-office sense, were long narrow > (about 1/4 inch wide) strips of thin springy metal with, > along their length, little flanges at right-angles to the > plane of the strip. Each little flange had a hole in it. > > The principle was that you would pinthe flanges to the > drawing-board at chosen points by pushing drawing-pins > through the holes. The metal strip then stood up at a > right-angle to the paper. > > The flanges were attached in such a way that you could > slide them along the metal strip. (Or you could use a > strip without flanges, and special pins which raised > little pillars up from the paper, against which the > spline would press.) > > The end result was that the metal strip then defined > a curve on the paper, and you could run a pencil along > it and draw a curve on the paper (taking care not to > press too hard against the metal, to avoid deforming > the curve). > > By virtue of the laws of elasticity, the curve delineated > by the metal strip had a continuous second derivative, i.e. > what modern kids call a second-derivative-continuous > piecewise cubic spline. > > We have not moved on. > > Happy whatever it is to all, > Ted. Ted, That sounds like the flexible curves that I found earlier, while Googling for an example of a French Curve and found the Mathworld link: http://www.artsupply.com/alvin/curves.htm and http://www.reuels.com/reuels/product21021.html Marc ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
