129 lines
3.0 KiB
C
129 lines
3.0 KiB
C
/*---------------------------------------------------------------------------*\
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========= |
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\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
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\\ / O peration |
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\\ / A nd | www.openfoam.com
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\\/ M anipulation |
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-------------------------------------------------------------------------------
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Copyright (C) 2011 OpenFOAM Foundation
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Copyright (C) 2024 OpenCFD Ltd.
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-------------------------------------------------------------------------------
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License
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This file is part of OpenFOAM.
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OpenFOAM is free software: you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with OpenFOAM. If not, see <http://www.gnu.org/licenses/>.
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\*---------------------------------------------------------------------------*/
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#include "interpolateSplineXY.H"
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#include "primitiveFields.H"
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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template<class Type>
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Foam::Field<Type> Foam::interpolateSplineXY
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(
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const scalarField& xNew,
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const scalarField& xOld,
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const Field<Type>& yOld
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)
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{
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Field<Type> yNew(xNew.size());
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forAll(xNew, i)
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{
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yNew[i] = interpolateSplineXY(xNew[i], xOld, yOld);
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}
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return yNew;
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}
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template<class Type>
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Type Foam::interpolateSplineXY
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(
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const scalar x,
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const scalarField& xOld,
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const Field<Type>& yOld
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)
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{
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label n = xOld.size();
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// early exit if out of bounds or only one value
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if (n == 1 || x <= xOld[0])
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{
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return yOld[0];
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}
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if (x >= xOld[n - 1])
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{
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return yOld[n - 1];
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}
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// linear interpolation if only two values
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if (n == 2)
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{
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return (x - xOld[0])/(xOld[1] - xOld[0])*(yOld[1] - yOld[0]) + yOld[0];
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}
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// find bounding knots
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label hi = 0;
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while (hi < n && xOld[hi] < x)
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{
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hi++;
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}
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label lo = hi - 1;
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const Type& y1 = yOld[lo];
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const Type& y2 = yOld[hi];
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Type y0;
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if (lo == 0)
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{
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y0 = 2*y1 - y2;
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}
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else
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{
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y0 = yOld[lo - 1];
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}
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Type y3;
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if (hi + 1 == n)
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{
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y3 = 2*y2 - y1;
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}
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else
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{
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y3 = yOld[hi + 1];
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}
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// weighting
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scalar mu = (x - xOld[lo])/(xOld[hi] - xOld[lo]);
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// interpolate
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return
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0.5
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*(
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2*y1
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+ mu
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*(
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-y0 + y2
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+ mu*((2*y0 - 5*y1 + 4*y2 - y3) + mu*(-y0 + 3*y1 - 3*y2 + y3))
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)
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);
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}
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// ************************************************************************* //
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