MeshElementGrid.h

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// SPDX-FileCopyrightText: Copyright (c) OpenGeoSys Community (opengeosys.org)
// SPDX-License-Identifier: BSD-3-Clause
 
#pragma once
 
#include <array>
#include <limits>
#include <vector>
 
#include "GeoLib/AABB.h"
#include "MathLib/Point3d.h"
 
namespace MeshLib {
 
// forward declarations
class Mesh;
class Element;

class MeshElementGrid final {
public:
    explicit MeshElementGrid(MeshLib::Mesh const& mesh);

    template <typename POINT>
    std::vector<MeshLib::Element const*> getElementsInVolume(
        POINT const& min, POINT const& max) const
    {
        auto const min_coords(getGridCellCoordinates(min));
        auto const max_coords(getGridCellCoordinates(max));
 
        std::vector<MeshLib::Element const*> elements_vec;
 
        const std::size_t n_plane(_n_steps[0]*_n_steps[1]);
        for (std::size_t i(min_coords.second[0]); i<=max_coords.second[0]; i++) {
            for (std::size_t j(min_coords.second[1]); j<=max_coords.second[1]; j++) {
                for (std::size_t k(min_coords.second[2]); k<=max_coords.second[2]; k++) {
                    std::size_t idx(i+j*_n_steps[0]+k*n_plane);
                    elements_vec.insert(end(elements_vec),
                                        begin(_elements_in_grid_box[idx]),
                                        end(_elements_in_grid_box[idx]));
                }
            }
        }
        return elements_vec;
    }

    Eigen::Vector3d const& getMinPoint() const;
    Eigen::Vector3d const& getMaxPoint() const;
 
private:
    void sortElementsInGridCells(MeshLib::Mesh const& mesh);
    bool sortElementInGridCells(MeshLib::Element const& element);
 
    GeoLib::AABB _aabb;
    std::pair<bool, std::array<std::size_t,3>>
        getGridCellCoordinates(MathLib::Point3d const& p) const;
    std::array<double,3> _step_sizes{};
    std::array<double,3> _inverse_step_sizes{};
    std::array<std::size_t,3> _n_steps;
    std::vector<std::vector<MeshLib::Element const*>> _elements_in_grid_box;
};
}  // namespace MeshLib