CatmullRomSpline.H

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    Copyright (C) 2020 OpenCFD Ltd.
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License
    This file is part of OpenFOAM.
 
    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
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    You should have received a copy of the GNU General Public License
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Class
    Foam::CatmullRomSpline
 
Description
    An implementation of Catmull-Rom splines
    (sometimes known as Overhauser splines).
 
    In this implementation, the end tangents are created automatically
    by reflection.
 
    In matrix form, the \e local interpolation on the interval t=[0..1] is
    described as follows:
    \verbatim
    P(t) = 1/2 * [ t^3 t^2 t 1 ] * [ -1  3 -3  1 ] * [ P-1 ]
                                   [  2 -5  4 -1 ]   [ P0 ]
                                   [ -1  0  1  0 ]   [ P1 ]
                                   [  0  2  0  0 ]   [ P2 ]
    \endverbatim
 
    Where P-1 and P2 represent the neighbouring points or the extrapolated
    end points. Simple reflection is used to automatically create the end
    points.
 
    The spline is discretized based on the chord length of the individual
    segments. In rare cases (sections with very high curvatures), the
    resulting distribution may be sub-optimal.
 
    A future implementation could also handle closed splines.
 
See also
    http://www.algorithmist.net/catmullrom.html provides a nice
    introduction
 
SourceFiles
    CatmullRomSpline.C
 
\*---------------------------------------------------------------------------*/
 
#ifndef CatmullRomSpline_H
#define CatmullRomSpline_H
 
#include "polyLine.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
 
/*---------------------------------------------------------------------------*\
                      Class CatmullRomSpline Declaration
\*---------------------------------------------------------------------------*/
 
class CatmullRomSpline
:
    public polyLine
{
public:
 
    // Constructors
 
        //- Construct from components
        explicit CatmullRomSpline
        (
            const pointField& knots,
            const bool notImplementedClosed = false
        );
 
 
    // Member Functions
 
        //- The point position corresponding to the curve parameter
        //  0 <= lambda <= 1
        point position(const scalar lambda) const;
 
        //- The point position corresponding to the local parameter
        //  0 <= lambda <= 1 on the given segment
        point position(const label segment, const scalar lambda) const;
 
        //- The length of the curve
        //  \note NotImplemented
        scalar length() const;
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //