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// ************************************************************************************************
//
// BornAgain: simulate and fit reflection and scattering
//
//! @file Img3D/Mesh/Ripple.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::meshRipple(float numSides, float ratio_asymmetry_W)
{
int const sides = qRound(numSides);
bool const smooth = (0 == sides); // sides = 0 implies smooth -> e.g. cosine ripple
int const slices = smooth ? 4 * SLICES : sides;
// Values are chosen such that length, width and height are 1
float const R = .5f;
float const H = 2 * R; // L = W = H = 2*R
float const asymmetry = ratio_asymmetry_W * 2 * R; // for CosineRipple asymmetry is inherently 0
Vertices vfront(slices), vback(slices);
if (numSides == 3) {
// SawtoothRipple: saw-tooth (3 rectangular sides and 2 triangular front and back)
vfront[0] = F3(-R, -R, 0);
vfront[1] = F3(-R, asymmetry, H);
vfront[2] = F3(-R, R, 0);
vback[0] = F3(R, -R, 0);
vback[1] = F3(R, asymmetry, H);
vback[2] = F3(R, R, 0);
} else if (numSides == 0) {
// CosineRipple: cosine ripple
for (int s = 0; s < slices; ++s) {
auto th = static_cast<float>(pi * s / (slices + 1));
float y = -R * cosf(th);
float z = R * (1.0f + cosf(2 * static_cast<float>(pi) * y / (2 * R)));
vfront[s] = F3(-R, y, z);
vback[s] = F3(R, y, z);
}
}
int const nv = (3 + 3 + 6) * slices; // 3 for part of front face, 3 for part of back face
// 6 for side face
Vertices vs;
vs.reserve(nv);
for (int s = 0; s < slices; ++s) {
int s1 = s, s2 = (s + 1) % slices;
// clockwise ordering of vertices
vs.addTriangle(vfront.at(s1), vfront.at(s2), F3(-R, asymmetry, H / 2)); // front
// counter-clockwise ordering of vertices
vs.addTriangle(vback.at(s1), F3(R, asymmetry, H / 2), vback.at(s2)); // back
// counter-clockwise ordering of vertices
vs.addQuad(vfront.at(s2), vfront.at(s1), vback.at(s1), vback.at(s2)); // side
}
ASSERT(vs.count() == nv);
return makeMesh(vs, nullptr); // normals not calculated here and left for makeMesh to calculate
}
} // namespace Img3D
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