BSpline.C

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#include "BSpline.H"
 
// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
Foam::point Foam::BSpline::position
(
    const label segmenti,
    const scalar segmentLambdaArg
) const
{
    // Quick return if segment index is out of range
    if (segmenti < 0) return start();
    if (segmenti >= nSegments()) return end();
 
    // Points bounding the segment
    const point& p0 = knots()[segmenti];
    const point& p1 = knots()[segmenti + 1];
 
    // Points before and after the segment. If at the ends, use reflection.
    const point pMinus1 =
        segmenti == 0 ? 2*p0 - p1 : knots()[segmenti - 1];
    const point p2 =
        segmenti == nSegments() - 1 ? 2*p1 - p0 : knots()[segmenti + 2];
 
    // Clip the argument
    const scalar segmentLambda =
        min(max(segmentLambdaArg, scalar(0)), scalar(1));
 
    // Evaluate the function and return
    const vector A = -pMinus1 + 3*p0 - 3*p1 + p2;
    const vector B = 3*pMinus1 - 6*p0 + 3*p1;
    const vector C = -3*pMinus1 + 3*p1;
    const vector D = pMinus1 + 4*p0 + p1;
    return (segmentLambda*(segmentLambda*(segmentLambda*A + B) + C) + D)/6;
}
 
 
// ************************************************************************* //