FEFLOWMeshInterface.cpp

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// SPDX-FileCopyrightText: Copyright (c) OpenGeoSys Community (opengeosys.org)
// SPDX-License-Identifier: BSD-3-Clause
 
#include "FEFLOWMeshInterface.h"
 
#include <boost/algorithm/string/trim.hpp>
#include <boost/tokenizer.hpp>
#include <cctype>
#include <fstream>
#include <memory>
 
#include "Applications/FileIO/FEFLOW/FEFLOWGeoInterface.h"
#include "BaseLib/FileTools.h"
#include "BaseLib/Logging.h"
#include "BaseLib/StringTools.h"
#include "GeoLib/Point.h"
#include "GeoLib/Polygon.h"
#include "MeshLib/Elements/Elements.h"
#include "MeshLib/Mesh.h"
#include "MeshLib/Node.h"
 
namespace FileIO
{
MeshLib::Mesh* FEFLOWMeshInterface::readFEFLOWFile(const std::string& filename)
{
    std::ifstream in(filename.c_str());
    if (!in)
    {
        ERR("FEFLOWMeshInterface::readFEFLOWFile(): Could not open file {:s}.",
            filename);
        return nullptr;
    }
 
    FEM_CLASS fem_class;
    FEM_DIM fem_dim;
    std::vector<GeoLib::Point*> points;
    std::vector<GeoLib::Polyline*> lines;
 
    bool isXZplane = false;
 
    std::vector<MeshLib::Node*> vec_nodes;
    std::vector<MeshLib::Element*> vec_elements;
 
    std::vector<std::vector<std::size_t>> vec_elementsets;
    std::vector<std::string> vec_element_property_names;
    std::vector<std::vector<double>> vec_element_property_values;
 
    std::string line_string;
    std::stringstream line_stream;
    while (!in.eof())
    {
        std::getline(in, line_string);
        boost::trim_right(line_string);
        //....................................................................
        // CLASS: the version number follows afterward, e.g. CLASS (v.5.313)
        if (line_string.find("CLASS") != std::string::npos)
        {
            std::getline(in, line_string);
            boost::trim_right(line_string);
            line_stream.str(line_string);
            // problem class, time mode, problem orientation, dimension, nr.
            // layers for 3D, saturation switch, precision of results, precision
            // of coordinates
            line_stream >> fem_class.problem_class >> fem_class.time_mode >>
                fem_class.orientation >> fem_class.dimension >>
                fem_class.n_layers3d;
            line_stream.clear();
        }
        //....................................................................
        // DIMENS
        else if (line_string == "DIMENS")
        {
            // DIMENS
            std::getline(in, line_string);
            line_stream.str(line_string);
            line_stream >> fem_dim.n_nodes >> fem_dim.n_elements >>
                fem_dim.n_nodes_of_element >> std::ws;
            // create node pointers with dummy coordinates to create element
            // objects.
            // True coordinates are set later in COOR and ELEV_I.
            vec_nodes.resize(fem_dim.n_nodes);
            std::size_t count = 0;
            double dummy_coords[3] = {};
            std::generate(vec_nodes.begin(), vec_nodes.end(), [&]()
                          { return new MeshLib::Node(dummy_coords, count++); });
            line_stream.clear();
        }
        //....................................................................
        // NODE (node index for elements)
        else if (line_string == "NODE")
        {
            assert(!vec_nodes.empty());
 
            MeshLib::MeshElemType eleType = MeshLib::MeshElemType::INVALID;
            if (fem_dim.n_nodes_of_element == 2)
            {
                eleType = MeshLib::MeshElemType::LINE;
            }
            else if (fem_dim.n_nodes_of_element == 3)
            {
                eleType = MeshLib::MeshElemType::TRIANGLE;
            }
            else if (fem_dim.n_nodes_of_element == 4 &&
                     fem_class.dimension == 2)
            {
                eleType = MeshLib::MeshElemType::QUAD;
            }
            else if (fem_dim.n_nodes_of_element == 4 &&
                     fem_class.dimension == 3)
            {
                eleType = MeshLib::MeshElemType::TETRAHEDRON;
            }
            else if (fem_dim.n_nodes_of_element == 6 &&
                     fem_class.dimension == 3)
            {
                eleType = MeshLib::MeshElemType::PRISM;
            }
            else if (fem_dim.n_nodes_of_element == 8 &&
                     fem_class.dimension == 3)
            {
                eleType = MeshLib::MeshElemType::HEXAHEDRON;
            }
 
            if (eleType == MeshLib::MeshElemType::INVALID)
            {
                ERR("FEFLOWInterface::readFEFLOWFile(): Unsupported element "
                    "type with the number of node = {:d} and dim = {:d}",
                    fem_dim.n_nodes_of_element, fem_class.dimension);
                std::for_each(vec_nodes.begin(), vec_nodes.end(),
                              [](MeshLib::Node* nod) { delete nod; });
                vec_nodes.clear();
                return nullptr;
            }
 
            vec_elements.reserve(fem_dim.n_elements);
            for (std::size_t i = 0; i < fem_dim.n_elements; i++)
            {
                std::getline(in, line_string);
                vec_elements.push_back(
                    readElement(fem_dim, eleType, line_string, vec_nodes));
            }
        }
        else if (line_string == "VARNODE")
        {
            assert(!vec_nodes.empty());
 
            vec_elements.reserve(fem_dim.n_elements);
            if (fem_dim.n_nodes_of_element == 0)
            {  // mixed element case
                if (!std::getline(in, line_string))
                {
                    ERR("FEFLOWInterface::readFEFLOWFile(): read element "
                        "error");
                    std::for_each(vec_nodes.begin(), vec_nodes.end(),
                                  [](MeshLib::Node* nod) { delete nod; });
                    vec_nodes.clear();
                    return nullptr;
                }
            }
 
            for (std::size_t i = 0; i < fem_dim.n_elements; i++)
            {
                std::getline(in, line_string);
                vec_elements.push_back(readElement(line_string, vec_nodes));
            }
        }
        //....................................................................
        // COOR
        else if (line_string == "COOR")
        {
            readNodeCoordinates(in, fem_class, fem_dim, vec_nodes);
        }
        else if (line_string == "XYZCOOR")
        {
            readNodeCoordinates(in, vec_nodes);
        }
        // ELEV_I
        else if (line_string == "ELEV_I")
        {
            if (fem_class.dimension == 2)
            {
                continue;
            }
            readElevation(in, fem_class, fem_dim, vec_nodes);
        }
        //....................................................................
        // GRAVITY
        else if (line_string == "GRAVITY")
        {
            std::getline(in, line_string);
            line_stream.str(line_string);
            double vec[3] = {};
            line_stream >> vec[0] >> vec[1] >> vec[2];
            if (vec[0] == 0.0 && vec[1] == -1.0 && vec[2] == 0.0)
            {
                // x-z plane
                isXZplane = true;
            }
            line_stream.clear();
        }
        //....................................................................
        // ELEMENTALSETS
        else if (line_string == "ELEMENTALSETS")
        {
            readELEMENTALSETS(in, vec_elementsets);
        }
        //....................................................................
        // SUPERMESH
        else if (line_string == "SUPERMESH")
        {
            FileIO::FEFLOWGeoInterface::readSuperMesh(in, fem_class.dimension,
                                                      points, lines);
        }
        //....................................................................
        // MAT_I_FLOW
        else if (line_string == "MAT_I_FLOW")
        {
            readMAT_I_FLOW(in, fem_dim, vec_element_property_names,
                           vec_element_property_values);
        }
        //....................................................................
    }
    in.close();
 
    INFO("Create mesh");
    std::string project_name(
        BaseLib::extractBaseNameWithoutExtension(filename));
    auto mesh(
        std::make_unique<MeshLib::Mesh>(project_name, vec_nodes, vec_elements));
    INFO("Set values for material property.");
    auto opt_material_ids(mesh->getProperties().createNewPropertyVector<int>(
        "MaterialIDs", MeshLib::MeshItemType::Cell, 1));
    if (!opt_material_ids)
    {
        WARN("Could not create PropertyVector for MaterialIDs in Mesh.");
    }
    else
    {
        opt_material_ids->resize(mesh->getNumberOfElements());
        setMaterialIDs(fem_class, fem_dim, lines, vec_elementsets, vec_elements,
                       *opt_material_ids);
    }
    if (!vec_element_property_names.empty())
    {
        for (unsigned prop_id = 0; prop_id < vec_element_property_names.size();
             prop_id++)
        {
            const std::string& property_name =
                vec_element_property_names[prop_id];
            const std::vector<double>& vec_property_values =
                vec_element_property_values[prop_id];
            assert(vec_property_values.size() == mesh->getNumberOfElements());
            auto opt_element_property_values(
                mesh->getProperties().createNewPropertyVector<double>(
                    property_name, MeshLib::MeshItemType::Cell, 1));
            if (!opt_element_property_values)
            {
                WARN("Could not create PropertyVector for {:s} in Mesh.",
                     property_name);
            }
            else
            {
                opt_element_property_values->resize(
                    mesh->getNumberOfElements());
                opt_element_property_values->assign(vec_property_values);
            }
        }
    }
 
    if (isXZplane)
    {
        for (auto* nod : vec_nodes)
        {
            (*nod)[2] = (*nod)[1];
            (*nod)[1] = 0.0;
        }
        if (!points.empty())
        {
            for (auto* pt : points)
            {
                (*pt)[2] = (*pt)[1];
                (*pt)[1] = .0;
            }
        }
    }
    for (auto* pt : points)
    {
        delete pt;
    }
    for (auto* line : lines)
    {
        delete line;
    }
    return mesh.release();
}
 
void FEFLOWMeshInterface::readNodeCoordinates(
    std::ifstream& in, std::vector<MeshLib::Node*>& vec_nodes)
{
    std::string line_string;
    char dummy_char;  // for comma(,)
 
    for (unsigned k = 0; k < vec_nodes.size(); ++k)
    {
        // read the line containing the coordinates as string
        if (!std::getline(in, line_string))
        {
            ERR("Could not read the node '{:d}'.", k);
            for (auto* n : vec_nodes)
            {
                delete n;
            }
            return;
        }
        std::stringstream line_stream;
        line_stream.str(line_string);
        // parse the particular coordinates from the string read above
        for (std::size_t i(0); i < 3; ++i)
        {
            if (!(line_stream >> (*vec_nodes[k])[i]))
            {
                ERR("Could not parse coordinate {:d} of node '{:d}'.", i, k);
                for (auto* n : vec_nodes)
                {
                    delete n;
                }
                return;
            }
            if (!(line_stream >> dummy_char) && i < 2)  // read comma
            {
                ERR("Could not parse node '{:d}'.", k);
                for (auto* n : vec_nodes)
                {
                    delete n;
                }
                return;
            }
        }
    }
}
 
void FEFLOWMeshInterface::readNodeCoordinates(
    std::ifstream& in, const FEM_CLASS& fem_class, const FEM_DIM& fem_dim,
    std::vector<MeshLib::Node*> const& vec_nodes)
{
    const std::size_t no_nodes_per_layer =
        (fem_class.dimension == 2)
            ? fem_dim.n_nodes
            : fem_dim.n_nodes / (fem_class.n_layers3d + 1);
    assert(no_nodes_per_layer > 0);
    const std::size_t n_lines = (no_nodes_per_layer - 1) / 12 + 1;
    const std::size_t n_layers =
        (fem_class.dimension == 3) ? fem_class.n_layers3d + 1 : 1;
    std::string line_string;
    std::stringstream line_stream;
    double x;
    char dummy_char;  // for comma(,)
    // x, y
    for (unsigned k = 0; k < 2; k++)
    {
        // each line
        for (std::size_t i = 0; i < n_lines; i++)
        {
            std::getline(in, line_string);
            line_stream.str(line_string);
            for (unsigned j = 0; j < 12; j++)
            {
                if (i * 12 + j >= no_nodes_per_layer)
                {
                    break;
                }
                line_stream >> x >> dummy_char;
                for (std::size_t l = 0; l < n_layers; l++)
                {
                    const std::size_t n = i * 12 + l * no_nodes_per_layer + j;
                    MeshLib::Node* m_nod = vec_nodes[n];
                    if (k == 0)
                    {
                        (*m_nod)[0] = x;
                    }
                    else
                    {
                        (*m_nod)[1] = x;
                    }
                }
            }
            line_stream.clear();
        }
    }
}
 
std::vector<std::size_t> FEFLOWMeshInterface::getIndexList(
    const std::string& str_ranges)
{
    std::vector<std::size_t> vec_node_IDs;
 
    // insert space before and after minus for splitting
    std::string str_ranges2(BaseLib::replaceString("-", " # ", str_ranges));
    BaseLib::trim(str_ranges2);
    auto splitted_str = BaseLib::splitString(str_ranges2, ' ');
    bool is_range = false;
    for (auto str : splitted_str)
    {
        if (str.empty())
        {
            continue;
        }
        if (str[0] == '#')
        {
            is_range = true;
        }
        else if (is_range)
        {
            const std::size_t start = vec_node_IDs.back();
            const auto end = BaseLib::str2number<std::size_t>(str);
            for (std::size_t i = start + 1; i < end + 1; i++)
            {
                vec_node_IDs.push_back(i);
            }
            is_range = false;
        }
        else
        {
            BaseLib::trim(str);
            vec_node_IDs.push_back(BaseLib::str2number<std::size_t>(str));
        }
    }
 
    return vec_node_IDs;
}
 
void FEFLOWMeshInterface::readElevation(std::ifstream& in,
                                        const FEM_CLASS& fem_class,
                                        const FEM_DIM& fem_dim,
                                        std::vector<MeshLib::Node*>& vec_nodes)
{
    const std::size_t no_nodes_per_layer =
        fem_dim.n_nodes / (fem_class.n_layers3d + 1);
    double z = .0;
    std::string str_nodeList;
    std::string line_string;
    std::stringstream line_stream;
    std::size_t l = 0;
    unsigned mode = 0;  // 0: exit, 1: slice no, 2: elevation value, 3:
                        // continued line of mode 2
    std::streamoff pos_prev_line = 0;
    while (true)
    {
        pos_prev_line = in.tellg();
        std::getline(in, line_string);
        boost::trim_right(line_string);
 
        // check mode
        auto columns = BaseLib::splitString(line_string, ' ');
        if (!in || std::isalpha(line_string[0]))
        {
            mode = 0;
        }
        else if (line_string.empty())
        {
            continue;
        }
        else if (line_string[0] == '\t')
        {
            mode = 3;
        }
        else if (columns.size() == 1)
        {
            mode = 1;
        }
        else
        {  // columns.size()>1
            mode = 2;
        }
 
        // process stocked data
        if (mode != 3 && !str_nodeList.empty())
        {
            // process previous lines
            auto vec_nodeIDs = getIndexList(str_nodeList);
            for (auto n0 : vec_nodeIDs)
            {
                const std::size_t n = n0 - 1 + l * no_nodes_per_layer;
                (*vec_nodes[n])[2] = z;
            }
            str_nodeList.clear();
        }
 
        if (mode == 0)
        {
            break;
        }
        if (mode == 1)
        {
            // slice number
            l++;
            assert(l + 1 == BaseLib::str2number<std::size_t>(columns.front()));
        }
        else if (mode == 2)
        {
            // parse current line
            line_stream.str(line_string);
            line_stream >> z;
            std::getline(line_stream, str_nodeList);
            boost::trim(str_nodeList);
            line_stream.clear();
        }
        else if (mode == 3)
        {
            // continue reading node range
            BaseLib::trim(line_string, '\t');
            str_nodeList += " " + line_string;
        }
    }
 
    // move stream position to previous line
    if (std::isalpha(line_string[0]))
    {
        in.seekg(pos_prev_line);
    }
}
 
MeshLib::Element* FEFLOWMeshInterface::readElement(
    std::string const& line, std::vector<MeshLib::Node*> const& nodes)
{
    std::stringstream ss(line);
 
    int ele_type;
    ss >> ele_type;
 
    MeshLib::MeshElemType elem_type;
    std::size_t n_nodes_of_element;
    switch (ele_type)
    {
        case 6:
            elem_type = MeshLib::MeshElemType::TETRAHEDRON;
            n_nodes_of_element = 4;
            break;
        case 7:
            elem_type = MeshLib::MeshElemType::PRISM;
            n_nodes_of_element = 6;
            break;
        case 8:
            elem_type = MeshLib::MeshElemType::HEXAHEDRON;
            n_nodes_of_element = 8;
            break;
        default:
            WARN("Could not parse element type.");
            return nullptr;
    }
 
    unsigned idx[8];
    for (std::size_t i = 0; i < n_nodes_of_element; ++i)
    {
        ss >> idx[i];
    }
    auto** ele_nodes = new MeshLib::Node*[n_nodes_of_element];
 
    switch (elem_type)
    {
        default:
            for (std::size_t k(0); k < n_nodes_of_element; ++k)
            {
                ele_nodes[k] = nodes[idx[k] - 1];
            }
            break;
        case MeshLib::MeshElemType::HEXAHEDRON:
        case MeshLib::MeshElemType::PRISM:
            const unsigned n_half_nodes = n_nodes_of_element / 2;
            for (unsigned k(0); k < n_half_nodes; ++k)
            {
                ele_nodes[k] = nodes[idx[k + n_half_nodes] - 1];
                ele_nodes[k + n_half_nodes] = nodes[idx[k] - 1];
            }
            break;
    }
 
    switch (elem_type)
    {
        case MeshLib::MeshElemType::TETRAHEDRON:
            return new MeshLib::Tet(ele_nodes);
        case MeshLib::MeshElemType::HEXAHEDRON:
            return new MeshLib::Hex(ele_nodes);
        case MeshLib::MeshElemType::PRISM:
            return new MeshLib::Prism(ele_nodes);
        default:
            return nullptr;
    }
}
 
MeshLib::Element* FEFLOWMeshInterface::readElement(
    const FEM_DIM& fem_dim, const MeshLib::MeshElemType elem_type,
    const std::string& line, const std::vector<MeshLib::Node*>& nodes)
{
    std::stringstream ss(line);
 
    unsigned idx[8];
    for (std::size_t i = 0; i < fem_dim.n_nodes_of_element; ++i)
    {
        ss >> idx[i];
    }
    auto** ele_nodes = new MeshLib::Node*[fem_dim.n_nodes_of_element];
 
    switch (elem_type)
    {
        default:
            for (unsigned k(0); k < fem_dim.n_nodes_of_element; ++k)
            {
                ele_nodes[k] = nodes[idx[k] - 1];
            }
            break;
        case MeshLib::MeshElemType::HEXAHEDRON:
        case MeshLib::MeshElemType::PRISM:
            const unsigned n_half_nodes = fem_dim.n_nodes_of_element / 2;
            for (unsigned k(0); k < n_half_nodes; ++k)
            {
                ele_nodes[k] = nodes[idx[k + n_half_nodes] - 1];
                ele_nodes[k + n_half_nodes] = nodes[idx[k] - 1];
            }
            break;
    }
 
    switch (elem_type)
    {
        case MeshLib::MeshElemType::LINE:
            return new MeshLib::Line(ele_nodes);
        case MeshLib::MeshElemType::TRIANGLE:
            return new MeshLib::Tri(ele_nodes);
        case MeshLib::MeshElemType::QUAD:
            return new MeshLib::Quad(ele_nodes);
        case MeshLib::MeshElemType::TETRAHEDRON:
            return new MeshLib::Tet(ele_nodes);
        case MeshLib::MeshElemType::HEXAHEDRON:
            return new MeshLib::Hex(ele_nodes);
        case MeshLib::MeshElemType::PRISM:
            return new MeshLib::Prism(ele_nodes);
        default:
            assert(false);
            return nullptr;
    }
}
 
void FEFLOWMeshInterface::readELEMENTALSETS(
    std::ifstream& in, std::vector<std::vector<std::size_t>>& vec_elementsets)
{
    auto compressSpaces = [](std::string const& str)
    {
        std::stringstream ss(str);
        std::string new_str;
        std::string word;
        while (ss)
        {
            ss >> word;
            new_str += " " + word;
        }
        return new_str;
    };
 
    std::string line_string;
    std::string str_idList;
    std::streampos pos_prev_line = 0;
    while (true)
    {
        pos_prev_line = in.tellg();
        std::getline(in, line_string);
 
        unsigned mode = 0;
        if (!in)
        {
            mode = 0;  // reached the end of the file
        }
        else if (line_string.empty())
        {
            continue;  // skip and see what comes next
        }
        else if (std::isalpha(line_string[0]))
        {
            mode = 0;  // reached the next section
        }
        else if (line_string[0] == ' ')
        {
            mode = 1;  // start of the element set definition
        }
        else if (line_string[0] == '\t')
        {
            mode = 2;  // continue the definition
        }
        else
        {
            ERR("Failed during parsing of an ELEMENTALSETS section in a FEFLOW "
                "file");
            break;
        }
 
        if (mode != 2 && !str_idList.empty())
        {
            vec_elementsets.push_back(getIndexList(str_idList));
            str_idList.clear();
        }
 
        if (mode == 0)
        {
            break;
        }
        if (mode == 1)
        {
            // starting a new set
            std::string set_name;
            std::string ids;
            BaseLib::trim(line_string, ' ');
            if (line_string[0] == '"')
            {  // multiple words
                auto pos = line_string.find_last_of('"');
                set_name = line_string.substr(1, pos - 1);  // without quotation
                ids = line_string.substr(pos + 1);
            }
            else
            {  // single word
                auto pos = line_string.find_first_of(' ');
                set_name = line_string.substr(0, pos);
                ids = line_string.substr(pos + 1);
            }
            INFO("Found an element group - {:s}", set_name.data());
            str_idList += compressSpaces(ids);
        }
        else
        {
            // continue reading a element ids
            BaseLib::trim(line_string, '\t');
            str_idList += compressSpaces(line_string);
        }
    }
    // move stream position to previous line
    if (std::isalpha(line_string[0]))
    {
        in.seekg(pos_prev_line);
    }
}
 
std::vector<double> FEFLOWMeshInterface::readMaterialPropertyValues(
    std::ifstream& in, std::size_t n_elements)
{
    std::vector<double> vec_element_values(n_elements);
 
    double property_value = 0;
    std::string str_elementList;
    std::string line_string;
    std::stringstream line_stream;
    unsigned prev_mode = 0;
    std::streamoff pos_prev_line = 0;
    while (true)
    {
        pos_prev_line = in.tellg();
        std::getline(in, line_string);
        boost::trim_right(line_string);
        if (line_string.empty())
        {
            continue;
        }
 
        // check mode
        unsigned mode = 0;  // 0: exit, 1: value + corresponding element
                            // numbers, 2: continued line of mode 1
        if ((!in || (line_string[0] != ' ' && line_string[0] != '\t')) &&
            prev_mode != 0)
        {
            mode = 0;
        }
        else if (line_string[0] != '\t')
        {
            mode = 1;
        }
        else if (line_string[0] == '\t')
        {
            mode = 2;
        }
        prev_mode = mode;
 
        // process stocked data
        if (mode != 2 && !str_elementList.empty())
        {
            // process previous lines
            auto vec_elementIDs = getIndexList(str_elementList);
            for (auto elementID : vec_elementIDs)
            {
                vec_element_values[elementID - 1] = property_value;
            }
            str_elementList.clear();
        }
 
        if (mode == 0)
        {
            // move stream position to previous line
            in.seekg(pos_prev_line);
            break;
        }
        if (mode == 1)
        {
            line_stream.str(line_string);
            line_stream >> property_value;
            std::getline(line_stream, str_elementList);
            boost::trim(str_elementList);
            line_stream.clear();
        }
        else if (mode == 2)
        {
            // continue reading node range
            boost::trim_if(line_string, boost::is_any_of("\t"));
            str_elementList += " " + line_string;
        }
    }
    return vec_element_values;
}
 
void FEFLOWMeshInterface::readMAT_I_FLOW(
    std::ifstream& in,
    const FEM_DIM& fem_dim,
    std::vector<std::string>& vec_element_property_names,
    std::vector<std::vector<double>>& vec_element_property_values)
{
    std::string line_string;
    std::stringstream line_stream;
 
    auto is_header_of_material_property = [](const std::string& line_string)
    {
        if (line_string.empty())
        {
            return false;
        }
        return static_cast<bool>(isdigit(line_string.at(0)));
    };
 
    auto is_end_of_MAT_I_FLOW = [](const std::string& line_string)
    { return (isalpha(line_string.at(0))); };
 
    auto get_material_property_name = [](const std::string& line_string)
    {
        using Tok = boost::tokenizer<boost::escaped_list_separator<char>>;
        Tok tok(line_string,
                boost::escaped_list_separator<char>('\\', ' ', '"'));
        std::vector<std::string> vec_str;
        for (auto const& t : tok)
        {
            if (!t.empty())
            {
                vec_str.push_back(t);
            }
        }
 
        if (vec_str.size() < 3)
        {
            return std::string("");
        }
        return vec_str[2];
    };
 
    std::streamoff pos_prev_line = 0;
    while (!in.eof())
    {
        pos_prev_line = in.tellg();
        std::getline(in, line_string);
        boost::trim_right(line_string);
        if (line_string.empty())
        {
            continue;
        }
        if (is_end_of_MAT_I_FLOW(line_string))
        {
            // move stream position to previous line
            in.seekg(pos_prev_line);
            break;
        }
 
        if (is_header_of_material_property(line_string))
        {
            const std::string property_name =
                get_material_property_name(line_string);
            if (!property_name.empty())
            {
                INFO("read element property {:s}", property_name);
                vec_element_property_names.push_back(property_name);
                vec_element_property_values.push_back(
                    readMaterialPropertyValues(in, fem_dim.n_elements));
            }
        }
    }
}
 
void FEFLOWMeshInterface::setMaterialIDs(
    FEM_CLASS const& fem_class,
    FEM_DIM const& fem_dim,
    std::vector<GeoLib::Polyline*> const& lines,
    std::vector<std::vector<std::size_t>> const& vec_elementsets,
    std::vector<MeshLib::Element*> const& vec_elements,
    MeshLib::PropertyVector<int>& material_ids)
{
    assert(material_ids.size() == vec_elements.size());
    if (!vec_elementsets.empty())
    {
        for (std::size_t matid = 0; matid < vec_elementsets.size(); ++matid)
        {
            auto& eids = vec_elementsets[matid];
            for (auto eid : eids)
            {
                material_ids[eid - 1] =
                    matid;  // Element IDs given by FEFLOW starts from one!
            }
        }
    }
    else if (!lines.empty())
    {
        for (std::size_t i = 0; i < vec_elements.size(); ++i)
        {
            auto const gpt = MeshLib::getCenterOfGravity(*vec_elements[i]);
            std::size_t matId = 0;
            for (std::size_t j = 0; j < lines.size(); j++)
            {
                GeoLib::Polyline const& poly = *lines[j];
                if (!poly.isClosed())
                {
                    continue;
                }
 
                GeoLib::Polygon polygon(poly, true);
                if (polygon.isPntInPolygon(gpt))
                {
                    matId = j;
                    break;
                }
            }
            material_ids[i] = matId;
        }
    }
    else if (fem_class.n_layers3d > 0)
    {
        const std::size_t no_nodes_per_layer =
            fem_dim.n_nodes / (fem_class.n_layers3d + 1);
        for (std::size_t i = 0; i < vec_elements.size(); i++)
        {
            MeshLib::Element* e = vec_elements[i];
            std::size_t e_min_nodeID = std::numeric_limits<std::size_t>::max();
            for (std::size_t j = 0; j < e->getNumberOfBaseNodes(); j++)
            {
                e_min_nodeID = std::min(e_min_nodeID, getNodeIndex(*e, j));
            }
            std::size_t layer_id = e_min_nodeID / no_nodes_per_layer;
            material_ids[i] = layer_id;
        }
    }
}
 
}  // namespace FileIO