src/Mod/MeshPart/App/MeshFlattening.cpp

// SPDX-License-Identifier: LGPL-2.1-or-later

/***************************************************************************
 *   Copyright (c) 2017 Lorenz Lechner                                     *
 *                                                                         *
 *   This file is part of the FreeCAD CAx development system.              *
 *                                                                         *
 *   This library is free software; you can redistribute it and/or         *
 *   modify it under the terms of the GNU Library General Public           *
 *   License as published by the Free Software Foundation; either          *
 *   version 2 of the License, or (at your option) any later version.      *
 *                                                                         *
 *   This library  is distributed in the hope that it will be useful,      *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU Library General Public License for more details.                  *
 *                                                                         *
 *   You should have received a copy of the GNU Library General Public     *
 *   License along with this library; see the file COPYING.LIB. If not,    *
 *   write to the Free Software Foundation, Inc., 59 Temple Place,         *
 *   Suite 330, Boston, MA  02111-1307, USA                                *
 *                                                                         *
 ***************************************************************************/

#include <map>
#include <set>
#include <vector>

#include <BRep_Tool.hxx>
#include <Geom_BSplineSurface.hxx>
#include <Geom_Surface.hxx>
#include <Poly_Triangulation.hxx>
#include <Standard_Version.hxx>
#include <TColStd_Array1OfReal.hxx>
#include <TopLoc_Location.hxx>

#include "MeshFlattening.h"
#include "MeshFlatteningLscmRelax.h"


std::vector<ColMat<double, 3>> getBoundaries(ColMat<double, 3> vertices, ColMat<long, 3> tris)
{
    // get a hashtable for all edges
    // e: v1, v2, num
    std::map<std::set<long>, std::vector<long>> hash_map;
    std::vector<std::set<long>> hash_list;
    std::map<long, std::vector<long>> neighbour_map;
    std::vector<long> edge_vector_0;
    std::vector<std::vector<long>> edge_vector;


    for (long i = 0; i < tris.rows(); i++) {
        for (long j = 0; j < 3; j++) {
            long k = j + 1;
            if (k == 3) {
                k = 0;
            }
            long v1 = tris(i, j);
            long v2 = tris(i, k);
            std::set<long> hash {v1, v2};
            hash_list.push_back(hash);
            if (v1 < v2) {
                hash_map[hash] = std::vector<long> {v1, v2, 0};
            }
            else {
                hash_map[hash] = std::vector<long> {v2, v1, 0};
            }
        }
    }
    for (auto& hash : hash_list) {
        hash_map[hash][2] += 1;
    }

    for (auto& hash : hash_map) {
        if (hash.second[2] == 1) {
            long v0 = hash.second[0];
            long v1 = hash.second[1];

            neighbour_map[v0].push_back(v1);
            neighbour_map[v1].push_back(v0);
        }
    }


    while (neighbour_map.size() != 0) {
        long start_index = neighbour_map.begin()->first;
        long close_index = start_index;
        long next_index = neighbour_map[start_index][1];
        long temporary_next;
        edge_vector_0.clear();
        edge_vector_0.push_back(close_index);
        edge_vector_0.push_back(start_index);
        neighbour_map.erase(start_index);
        edge_vector_0.push_back(next_index);
        while (next_index != close_index) {
            temporary_next = neighbour_map[next_index][0];
            if (temporary_next != start_index) {
                start_index = next_index;
                next_index = temporary_next;
            }
            else {
                start_index = next_index;
                next_index = neighbour_map[start_index][1];
            }
            neighbour_map.erase(start_index);
            edge_vector_0.push_back(next_index);
        }
        edge_vector.push_back(edge_vector_0);
    }
    std::vector<ColMat<double, 3>> edges;
    for (auto& edge : edge_vector) {
        ColMat<double, 3> edge_vertices;
        edge_vertices.resize(edge.size(), 3);
        int i = 0;
        for (auto index : edge) {
            edge_vertices.row(i) = vertices.row(index);
            i++;
        }
        edges.push_back(edge_vertices);
    }
    return edges;
}

FaceUnwrapper::FaceUnwrapper(const TopoDS_Face& face)
{
    long i = 0;
    //  transform to nurbs:
    TopLoc_Location location;

    //  triangulate:
    const Handle(Poly_Triangulation) & triangulation = BRep_Tool::Triangulation(face, location);

    if (triangulation.IsNull()) {
        throw std::runtime_error("Null triangulation in face construction");
    }

    Standard_Integer numNodes = triangulation->NbNodes();
    Standard_Integer numTriangles = triangulation->NbTriangles();

    //  compute uv coordinates
    if (triangulation->HasUVNodes()) {
        this->uv_nodes.resize(numNodes, 2);
        i = 0;
        for (Standard_Integer index = 1; index <= numNodes; ++index) {
            const gp_Pnt2d& _uv_node = triangulation->UVNode(index);
            this->uv_nodes.row(i) << _uv_node.X(), _uv_node.Y();
            i++;
        }
    }
    //
    this->xyz_nodes.resize(numNodes, 3);
    i = 0;
    for (Standard_Integer index = 1; index <= numNodes; ++index) {
        gp_Pnt _node = triangulation->Node(index);
        this->xyz_nodes.row(i) << _node.X(), _node.Y(), _node.Z();
        i++;
    }

    this->tris.resize(numTriangles, 3);
    i = 0;
    for (Standard_Integer index = 1; index <= numTriangles; ++index) {
        int n1, n2, n3;
        const Poly_Triangle& _tri = triangulation->Triangle(index);
        _tri.Get(n1, n2, n3);
        this->tris.row(i) << n1 - 1, n2 - 1, n3 - 1;
        i++;
    }
}

void FaceUnwrapper::findFlatNodes(int steps, double val)
{
    std::vector<long> fixed_pins;  // TODO: INPUT
    lscmrelax::LscmRelax mesh_flattener(this->xyz_nodes.transpose(), this->tris.transpose(), fixed_pins);
    mesh_flattener.lscm();
    for (int j = 0; j < steps; j++) {
        mesh_flattener.relax(val);
    }
    this->ze_nodes = mesh_flattener.flat_vertices.transpose();
}

ColMat<double, 3> FaceUnwrapper::interpolateFlatFace(const TopoDS_Face& face)
{
    if (this->uv_nodes.size() == 0) {
        throw(std::runtime_error(
            "no uv-coordinates found, interpolating with nurbs is only "
            "possible if the flattener was constructed with a nurbs."
        ));
    }

    // extract xyz poles, knots, weights, degree
    const Handle(Geom_Surface) & _surface = BRep_Tool::Surface(face);
    const Handle(Geom_BSplineSurface) & _bspline = Handle(Geom_BSplineSurface)::DownCast(_surface);

    const TColStd_Array1OfReal& _uknots = _bspline->UKnotSequence();
    const TColStd_Array1OfReal& _vknots = _bspline->VKnotSequence();

    Eigen::VectorXd weights;
    weights.resize(
        static_cast<Eigen::Index>(_bspline->NbUPoles())
        * static_cast<Eigen::Index>(_bspline->NbVPoles())
    );
    long i = 0;
    for (long u = 1; u <= _bspline->NbUPoles(); u++) {
        for (long v = 1; v <= _bspline->NbVPoles(); v++) {
            weights[i] = _bspline->Weight(u, v);
            i++;
        }
    }

    Eigen::VectorXd u_knots;
    Eigen::VectorXd v_knots;
    u_knots.resize(_uknots.Length());
    v_knots.resize(_vknots.Length());
    for (long u = 1; u <= _uknots.Length(); u++) {
        u_knots[u - 1] = _uknots.Value(u);
    }
    for (long v = 1; v <= _vknots.Length(); v++) {
        v_knots[v - 1] = _vknots.Value(v);
    }


    nu = nurbs::NurbsBase2D(u_knots, v_knots, weights, _bspline->UDegree(), _bspline->VDegree());
    A = nu.getInfluenceMatrix(this->uv_nodes);

    Eigen::LeastSquaresConjugateGradient<spMat> solver;
    solver.compute(A);
    ColMat<double, 2> ze_poles;
    ColMat<double, 3> flat_poles;
    ze_poles.resize(weights.rows(), 2);
    flat_poles.resize(weights.rows(), 3);
    flat_poles.setZero();
    ze_poles = solver.solve(ze_nodes);
    flat_poles.col(0) << ze_poles.col(0);
    flat_poles.col(1) << ze_poles.col(1);
    return flat_poles;
}


FaceUnwrapper::FaceUnwrapper(ColMat<double, int(3)> xyz_nodes, ColMat<long int, int(3)> tris)
{
    this->tris = tris;
    this->xyz_nodes = xyz_nodes;
}

std::vector<ColMat<double, 3>> FaceUnwrapper::getFlatBoundaryNodes()
{
    if (this->ze_nodes.size() == 0) {
        throw(std::runtime_error("Flat vertices not yet computed"));
    }

    ColMat<double, 3> flat_vertices;
    flat_vertices.resize(this->ze_nodes.rows(), 3);
    flat_vertices.setZero();
    flat_vertices.col(0) << this->ze_nodes.col(0);
    flat_vertices.col(1) << this->ze_nodes.col(1);
    return getBoundaries(flat_vertices, this->tris);
}