createMeshFromElementSelection.cpp

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// SPDX-FileCopyrightText: Copyright (c) OpenGeoSys Community (opengeosys.org)
// SPDX-License-Identifier: BSD-3-Clause
 
#include "createMeshFromElementSelection.h"
 
#include <range/v3/numeric.hpp>
#include <range/v3/range/conversion.hpp>
#include <range/v3/view/enumerate.hpp>
#include <range/v3/view/indirect.hpp>
#include <range/v3/view/map.hpp>
#include <unordered_map>
 
#include "MeshLib/Elements/Element.h"
#include "MeshLib/Mesh.h"
#include "MeshLib/Node.h"
#include "MeshLib/Utils/addPropertyToMesh.h"
 
namespace MeshLib
{
std::unique_ptr<MeshLib::Mesh> createMeshFromElementSelection(
    std::string mesh_name, std::vector<MeshLib::Element*> const& elements)
{
    auto ids_vector = views::ids | ranges::to<std::vector>();
 
    DBUG("Found {:d} elements in the mesh", elements.size());
 
    // Store bulk element ids for each of the new elements.
    auto bulk_element_ids = elements | ids_vector;
 
    // original node ids to newly created nodes.
    std::unordered_map<std::size_t, MeshLib::Node*> id_node_hash_map;
    id_node_hash_map.reserve(
        elements.size());  // There will be at least one node per element.
 
    for (auto& e : elements)
    {
        // For each node find a cloned node in map or create if there is none.
        unsigned const n_nodes = e->getNumberOfNodes();
        for (unsigned i = 0; i < n_nodes; ++i)
        {
            const MeshLib::Node* n = e->getNode(i);
            auto const it = id_node_hash_map.find(n->getID());
            if (it == id_node_hash_map.end())
            {
                auto new_node_in_map = id_node_hash_map[n->getID()] =
                    new MeshLib::Node(*n);
                e->setNode(i, new_node_in_map);
            }
            else
            {
                e->setNode(i, it->second);
            }
        }
    }
 
    std::map<std::size_t, MeshLib::Node*> nodes_map;
    for (const auto& n : id_node_hash_map)
    {
        nodes_map[n.first] = n.second;
    }
 
    // Copy the unique nodes pointers.
    auto element_nodes =
        nodes_map | ranges::views::values | ranges::to<std::vector>;
 
    // Store bulk node ids for each of the new nodes.
    auto bulk_node_ids =
        nodes_map | ranges::views::keys | ranges::to<std::vector>;
 
    auto mesh = std::make_unique<MeshLib::Mesh>(
        std::move(mesh_name), std::move(element_nodes), std::move(elements),
        true /* compute_element_neighbors */);
    assert(mesh != nullptr);
 
    addPropertyToMesh<std::size_t>(
        *mesh, getBulkIDString(MeshLib::MeshItemType::Cell),
        MeshLib::MeshItemType::Cell, 1, {bulk_element_ids});
    addPropertyToMesh<std::size_t>(
        *mesh, getBulkIDString(MeshLib::MeshItemType::Node),
        MeshLib::MeshItemType::Node, 1, {bulk_node_ids});
 
    return mesh;
}
 
}  // namespace MeshLib