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// ************************************************************************************************
//
// BornAgain: simulate and fit reflection and scattering
//
//! @file Img3D/Mesh/Column.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 "Img3D/Model/Geometry.h"
#include <numbers>
using std::numbers::pi;
namespace Img3D {
Geometry::Mesh Geometry::meshColumn(float ratio_Rt_Rb, float numSides)
{
int const sides = qRound(numSides);
bool const smooth = (0 == sides); // sides = 0 implies smooth -> e.g. cylinder
int const slices = smooth ? SLICES : sides;
// Rt is the top radius, Rb is the bottom radius, H is the height
// Values are chosen such that diameter and height are 1
float const R = .5f;
float Rb = R, Rt = Rb * ratio_Rt_Rb, H = 2 * R;
// mesh of vertices (bottom and top) and normals
Vertices vb(slices), vt(slices), nbt(slices);
float const nz = (1 - Rt / Rb) * H;
for (int s = 0; s < slices; ++s) {
float th = float((2 * pi) * s / slices), st = sinf(th), ct = cosf(th);
F3 vb_(Rb * ct, Rb * st, 0), vt_(Rt * ct, Rt * st, H);
vb[s] = vb_;
vt[s] = vt_;
if (smooth)
nbt[s] = F3(vb_.x(), vb_.y(), nz).normalized();
}
// make into triangles
int const nv = 6 * 2 * slices;
Vertices vs;
vs.reserve(nv);
Vertices ns;
if (smooth)
ns.reserve(nv);
for (int s = 0; s < slices; ++s) {
int s1 = s, s2 = (s + 1) % slices;
vs.addTriangle(vb.at(s1), F3(0, 0, 0), vb.at(s2)); // bottom
if (smooth)
ns.addVertex(F3(0, 0, -1), 3);
vs.addTriangle(F3(0, 0, H), vt.at(s1), vt.at(s2)); // top
if (smooth)
ns.addVertex(F3(0, 0, 1), 3);
vs.addQuad(vb.at(s1), vb.at(s2), vt.at(s2), vt.at(s1)); // side
if (smooth) {
auto &n1 = nbt.at(s1), &n2 = nbt.at(s2);
ns.addQuad(n1, n2, n2, n1);
}
}
ASSERT(vs.count() == nv);
ASSERT(!smooth || ns.count() == nv);
return makeMesh(vs, smooth ? &ns : nullptr);
}
} // namespace Img3D
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