IShape3D.cpp

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//  ************************************************************************************************
//
//  BornAgain: simulate and fit reflection and scattering
//
//! @file      Sample/Shapes/IShape3D.cpp
//! @brief     Implements default methods of interface IShape3D.
//!
//! @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/Shapes/IShape3D.h"
 
#include <cmath>
 
// Value of 24 ensures that real points stick out of the convex hull at most
// 1% of the radius
const size_t IShape3D::N_Circle = 24;
 
std::vector<R3> IShape3D::vertices() const
{
    return m_vertices;
}
 
std::vector<R3> RectangleVertices(double length, double width, double z)
{
    std::vector<R3> result = {{length / 2.0, width / 2.0, z},
                              {-length / 2.0, width / 2.0, z},
                              {-length / 2.0, -width / 2.0, z},
                              {length / 2.0, -width / 2.0, z}};
    return result;
}
 
std::vector<R3> EllipseVerticesZ(double r_x, double r_y, double z)
{
    static constexpr double delta_angle = 2.0 * M_PI / IShape3D::N_Circle;
    std::vector<R3> result(IShape3D::N_Circle);
    for (size_t i = 0; i < IShape3D::N_Circle; ++i) {
        double angle = i * delta_angle;
        double x = r_x * std::cos(angle);
        double y = r_y * std::sin(angle);
        result[i] = R3(x, y, z);
    }
    return result;
}
 
std::vector<R3> EllipseVerticesXtrunc(double x, double r_y, double r_z, double z_b, double z_t)
{
    static constexpr double delta_angle = 2.0 * M_PI / IShape3D::N_Circle;
    // for full ellipse
    //    std::vector<R3> result(IShape3D::N_Circle);
    //    for (size_t i = 0; i < IShape3D::N_Circle; ++i) {
    //        double angle = i * delta_angle;
    //        double y = r_y * std::cos(angle);
    //        double z = r_z * std::sin(angle) + r_z; // bottom is at 0, top at 2*r_z
    //        result[i] = R3(x, y, z);
    //    }
 
    // for truncated ellipse
    std::vector<R3> result;
    result.reserve(IShape3D::N_Circle + 4);
    for (size_t i = 0; i < IShape3D::N_Circle; ++i) {
        double angle = i * delta_angle;
        double y = r_y * std::cos(angle);
        double z = r_z * std::sin(angle) - z_b; // bottom is at 0, top at z_t-z_b
 
        if (0 <= z && z <= (z_t - z_b)) {
            result.push_back(R3(x, y, z));
        }
    }
    double alpha_t = atan(z_t / sqrt(r_z * r_z - z_t * z_t) * r_z / r_y);
    double alpha_b = atan(z_b / sqrt(r_z * r_z - z_b * z_b) * r_z / r_y);
 
    double y_t = r_y * std::cos(alpha_t);
    double y_b = r_y * std::cos(alpha_b);
 
    result.push_back(R3(x, y_t, z_t - z_b));
    result.push_back(R3(x, -y_t, z_t - z_b));
    result.push_back(R3(x, y_b, 0));
    result.push_back(R3(x, -y_b, 0));
 
    return result;
}