cuboctahedron.cpp

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//  ************************************************************************************************
//
//  BornAgain: simulate and fit reflection and scattering
//
//! @file      GUI/ba3d/mesh/cuboctahedron.cpp
//! @brief     Implements utility functions in ba3d namespace
//!
//! @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 "Base/Util/Assert.h"
#include "GUI/ba3d/model/geometry.h"
#include <qmath.h>
 
namespace GUI::RealSpace {
 
Geometry::Mesh Geometry::meshBipyramid4(float rH, float alpha, float H)
{ // t/D
 
    // alpha is the angle between the common square interface and one of the side faces (alpha for
    // both the two truncated pyramids is the same)
 
    // H here is the normalized height of the cuboctahedron i.e. H/L (see particles.cpp)
 
    ASSERT(alpha <= float(M_PI_2));
    ASSERT(rH >= 0);
 
    float const D = .5f, t = tanf(float(M_PI_2) - alpha);
    float const Db = D - t * H, Dt = D - t * rH * H;
 
    Vertices vs_;
    vs_.reserve(12);
    float z[] = {0, H, H * (rH + 1)},
          d[] = {Db, D, Dt}; // keep bottom of the cuboctahedron in z=0 plane
    for (int i = 0; i < 3; ++i)
        for (int x : {-1, +1})
            for (int y : {-1, +1}) {
                float di = d[i];
                vs_.append(Vector3D(x * di, y * di, z[i]));
            }
 
    ASSERT(12 == vs_.count());
 
    Vertices vs;
    vs.reserve(60);
 
    vs.addQuad(vs_, 0, 1, 3, 2);
    vs.addQuad(vs_, 8, 10, 11, 9);
    vs.addQuad(vs_, 0, 4, 5, 1);
    vs.addQuad(vs_, 1, 5, 7, 3);
    vs.addQuad(vs_, 3, 7, 6, 2);
    vs.addQuad(vs_, 2, 6, 4, 0);
    vs.addQuad(vs_, 4, 8, 9, 5);
    vs.addQuad(vs_, 5, 9, 11, 7);
    vs.addQuad(vs_, 7, 11, 10, 6);
    vs.addQuad(vs_, 6, 10, 8, 4);
 
    ASSERT(60 == vs.count());
 
    return makeMesh(vs);
}
 
} // namespace GUI::RealSpace