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Flat spline

Long flexible batten used to produce a fair curve through a set of points

Flat spline

Long flexible batten used to produce a fair curve through a set of points

A spline

A spline consists of a long strip fixed in position at a number of points whose tension creates a smooth curve passing through those points, for the purpose of transferring that curve to another material.

Before computers were used for creating engineering designs, drafting tools were employed by designers drawing by hand.{{cite web |access-date = 2012-02-24}} To draw curves, especially for shipbuilding, draftsmen often used long, thin, flexible strips of wood, plastic, or metal called splines (or laths, not to be confused with lathes). The splines were held in place with lead weights (called ducks because of their duck-like shape). The elasticity of the spline material combined with the constraint of the control points, or knots, would cause the strip to take the shape that minimized the energy required for bending it between the fixed points, this being the smoothest possible shape.

One can recreate an original draftsman's spline device with weights and a length of thin plastic or wood, flexible to bend enough without breaking. Crosses are marked on the paper to designate the knots or control points. The spline is placed on the drafting paper, and weights are attached to the shaft near each knot so that the spline passes through each one. Once adjusted to the satisfaction of the drafter, a line may be traced along the shaft, creating a template for a smooth curve.

Etymology and history

The Oxford English Dictionary finds the first recorded usage in the 18th century in East Anglia, England, and suggests the term spline may be related to splinter.

Spline devices have been used to designs shapes for pianos, violins, and other wooden instruments. The Wright brothers used one to shape the wings of their aircraft.

Mathematical splines

By 1946, mathematicians had begun to devise mathematical formulae to serve a similar purpose, and ultimately created efficient algorithms to find piecewise polynomial curves, also known as splines, that go smoothly through designated points. This has led to the widespread use of such functions in computer-aided design, especially in the surface designs of vehicles, replacing the draftsman's spline. I. J. Schoenberg gave the spline function its name after its resemblance to the mechanical spline used by draftsmen.{{cite journal |doi-access = free

Other curve drawing tools

References

References

  1. Stephens, William Picard. (1889). "Canoe and Boat Building: A Complete Manual for Amateurs.". Forest and Stream Publishing Company.
  2. Newsam, G. N.. (1991). "Some topical variational geometry problems in computer graphics". Centre for Mathematics and its Applications, Mathematical Sciences Institute, The Australian National University.
  3. Fowler, H. W. (Henry Watson), 1858-1933.. (2011). "The concise Oxford dictionary of current English : 1911 first edition". Oxford University Press.
  4. "Solving geoscience problems with math {{!}} UCAR Center for Science Education".
  5. Schoenberg, I. J.. (1946). "Contributions to the problem of approximation of equidistant data by analytic functions. Part A. On the problem of smoothing or graduation. A first class of analytic approximation formulae". Quarterly of Applied Mathematics.
  6. Grandine, Thomas. (May 2005). "The Extensive Use of Splines at Boeing". Society for Industrial and Applied Mathematics.
  7. {{OED. lesbian rule
  8. (1989). "Intertester reliability of the flexible ruler for the cervical spine". The Journal of Orthopaedic and Sports Physical Therapy.
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This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

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