FormFactorCone6.cpp

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// ************************************************************************** //
//
//  BornAgain: simulate and fit scattering at grazing incidence
//
//! @file      Sample/HardParticle/FormFactorCone6.cpp
//! @brief     Implements class FormFactorCone6.
//!
//! @homepage  http://www.bornagainproject.org
//! @license   GNU General Public License v3 or higher (see COPYING)
//! @copyright Forschungszentrum Jülich GmbH 2018
//! @authors   Scientific Computing Group at MLZ (see CITATION, AUTHORS)
//
// ************************************************************************** //
 
#include "Sample/HardParticle/FormFactorCone6.h"
#include "Base/Const/MathConstants.h"
#include "Base/Types/Exceptions.h"
#include "Base/Utils/MathFunctions.h"
 
const PolyhedralTopology FormFactorCone6::topology = {{{{5, 4, 3, 2, 1, 0}, true},
                                                       {{0, 1, 7, 6}, false},
                                                       {{1, 2, 8, 7}, false},
                                                       {{2, 3, 9, 8}, false},
                                                       {{3, 4, 10, 9}, false},
                                                       {{4, 5, 11, 10}, false},
                                                       {{5, 0, 6, 11}, false},
                                                       {{6, 7, 8, 9, 10, 11}, true}},
                                                      false};
 
FormFactorCone6::FormFactorCone6(const std::vector<double> P)
    : IFormFactorPolyhedron(
        {"Cone6",
         "frustum with regular hexagonal base",
         {{"BaseEdge", "nm", "base edge length", 0, +INF, 0},
          {"Height", "nm", "height", 0, +INF, 0},
          {"Alpha", "rad", "angle between base and a side face", 0., M_PI_2, 0}}},
        P),
      m_base_edge(m_P[0]), m_height(m_P[1]), m_alpha(m_P[2])
{
    onChange();
}
 
FormFactorCone6::FormFactorCone6(double base_edge, double height, double alpha)
    : FormFactorCone6(std::vector<double>{base_edge, height, alpha})
{
}
 
IFormFactor* FormFactorCone6::sliceFormFactor(ZLimits limits, const IRotation& rot,
                                              kvector_t translation) const
{
    auto effects = computeSlicingEffects(limits, translation, m_height);
    double dbase_edge = effects.dz_bottom * MathFunctions::cot(m_alpha);
    FormFactorCone6 slicedff(m_base_edge - dbase_edge,
                             m_height - effects.dz_bottom - effects.dz_top, m_alpha);
    return createTransformedFormFactor(slicedff, rot, effects.position);
}
 
void FormFactorCone6::onChange()
{
    double cot_alpha = MathFunctions::cot(m_alpha);
    if (!std::isfinite(cot_alpha) || cot_alpha < 0)
        throw Exceptions::OutOfBoundsException("pyramid angle alpha out of bounds");
    double r = cot_alpha * 2 / sqrt(3) * m_height / m_base_edge; // L(top)/L(base)
    if (r > 1) {
        std::ostringstream ostr;
        ostr << "Incompatible parameters in Cone6 ";
        ostr << "(base_edge=" << m_base_edge;
        ostr << ", height:" << m_height;
        ostr << ", alpha[rad]:" << m_alpha << ")";
        throw Exceptions::ClassInitializationException(ostr.str());
    }
 
    double a = m_base_edge;
    double as = a / 2;
    double ac = a * sqrt(3) / 2;
    double b = a * (1 - r);
    double bs = b / 2;
    double bc = b * sqrt(3) / 2;
 
    double zcom = m_height * (.5 - 2 * r / 3 + r * r / 4) / (1 - r + r * r / 3); // center of mass
 
    setPolyhedron(topology, -zcom,
                  {// base:
                   {a, 0., -zcom},
                   {as, ac, -zcom},
                   {-as, ac, -zcom},
                   {-a, 0., -zcom},
                   {-as, -ac, -zcom},
                   {as, -ac, -zcom},
                   // top:
                   {b, 0., m_height - zcom},
                   {bs, bc, m_height - zcom},
                   {-bs, bc, m_height - zcom},
                   {-b, 0., m_height - zcom},
                   {-bs, -bc, m_height - zcom},
                   {bs, -bc, m_height - zcom}});
}