circlepoints.hh

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// -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
// vi: set et ts=4 sw=4 sts=4:
//
// SPDX-FileCopyrightInfo: Copyright © DuMux Project contributors, see AUTHORS.md in root folder
// SPDX-License-Identifier: GPL-3.0-or-later
//
#ifndef DUMUX_MULTIDOMAIN_EMBEDDED_CIRCLEPOINTS_HH
#define DUMUX_MULTIDOMAIN_EMBEDDED_CIRCLEPOINTS_HH
 
#include <vector>
#include <cmath>
 
#include <dune/common/exceptions.hh>
 
#include <dumux/common/math.hh>
#include <dumux/geometry/normal.hh>
 
namespace Dumux::EmbeddedCoupling {
 
template<class GlobalPosition, class Scalar>
void circlePoints(std::vector<GlobalPosition>& points,
                  const std::vector<Scalar>& sincos,
                  const GlobalPosition& center,
                  const GlobalPosition& normal,
                  const Scalar radius)
{
    assert(sincos.size() % 2 == 0 && "Sample angles have to be pairs of sin/cos so size needs to be even.");
    static_assert(GlobalPosition::dimension == 3, "Only implemented for world dimension 3");
 
    // resize the points vector
    const std::size_t numPoints = sincos.size()/2;
    points.resize(numPoints);
 
    // make sure n is a unit vector
    auto n = normal;
    n /= n.two_norm();
 
    // calculate a vector u perpendicular to n
    auto u = unitNormal(n); u*= radius;
 
    // the circle parameterization is p(t) = r*cos(t)*u + r*sin(t)*(n x u) + c
    auto tangent = crossProduct(u, n);
    tangent *= radius/tangent.two_norm();
 
    // insert the vertices
    for (std::size_t i = 0; i < numPoints; ++i)
    {
        points[i] = GlobalPosition({u[0]*sincos[2*i+1] + tangent[0]*sincos[2*i] + center[0],
                                    u[1]*sincos[2*i+1] + tangent[1]*sincos[2*i] + center[1],
                                    u[2]*sincos[2*i+1] + tangent[2]*sincos[2*i] + center[2]});
    }
}
 
template<class Scalar = double>
std::vector<Scalar> circlePointsSinCos(const std::size_t numPoints)
{
    std::vector<Scalar> sincos(2*numPoints);
    Scalar t = 0 + 0.1; // add arbitrary offset
    for (std::size_t i = 0; i < numPoints; ++i)
    {
        using std::sin; using std::cos;
        sincos[2*i] = sin(t);
        sincos[2*i + 1] = cos(t);
        t += 2*M_PI/numPoints;
        if(t > 2*M_PI) t -= 2*M_PI;
    }
    return sincos;
}
 
template<class GlobalPosition, class Scalar>
std::vector<GlobalPosition> circlePoints(const GlobalPosition& center,
                                         const GlobalPosition& normal,
                                         const Scalar radius,
                                         const std::size_t numPoints = 20)
{
    // precompute the sin/cos values
    const auto sincos = circlePointsSinCos<Scalar>(numPoints);
 
    std::vector<GlobalPosition> points;
    circlePoints(points, sincos, center, normal, radius);
    return points;
}
 
} // end namespace Dumux::EmbeddedCoupling
 
#endif