Multi degree splines (MD-splines, for short) are piecewise functions comprised of
polynomial segments of different degrees.
They were proposed in the seminal paper  and they have been a subject of study
in several recent works , , , ,  and .
To model a shape, the MD-splines use, in addition to the knot interval and control points, an additional parameter, the degree.
The degree can be chosen locally to get the best shape fitting,
thus allowing to use less control points than those necessary with conventional splines (the latter being intended as spline
spaces where every piece is spanned by polynomials of the same degree).
At the same time, MD-splines reduce to conventional splines when all segments are of the same degree, thus generalizing the
With C1 MD-splines we mean a subclass where, between two segments of different degrees, is allowed at most C1 continuity.
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