B-spline
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Nonuniform Rational B-Splines are a mathematical tool for the definition of geometric shapes.
Used extensively in the CAD industry and more widely in computing for 3D geometry generation and modelling because of their accuracy, flexibility, commonality of mathematical form for both standard geometric shapes and free-form shapes, fast algorithms, invariance under affine and perspective transformations, and that they are generalizations of non-rational B-splines and both types of Bezier curves and surfaces.
See also:
This article (or an earlier version of it) contains material from FOLDOC, used with permission.