MultipleBuilding Class Presentation

This guide explains how to use the MultipleBuilding class to create building models, with a focus on the correct method order, optional method usage, and how to extract results at each stage.

1. Overview

The MultipleBuilding class provides methods for creating and processing building models. Proper sequencing of method calls is essential for accurate results. Some methods are optional, depending on your needs, while others have specific prerequisites.

Every parameters that will be used is detailed in the Parameters Section.

2. Method Call Order

Follow this sequence to ensure proper functionality of the MultipleBuilding class:

  1. Load Building Data:

    • Call loadFromJsonGis(json) or loadFromJsonDat(json) to load building data.

  2. Triangulate Base Polygon:

    • Use triangulateBasePolygon(index) to prepare the base polygon.

    • Extract Result: Use getBaseMeshes() to retrieve the base meshes.

  3. Extrude Base Polygon:

    • Call extrudeBasePolygon(index) to create initial walls from the base polygon.

    • Extract Result: Use getBaseMeshes() to retrieve the extruded base meshes.

  4. Extrude Walls:

    • Use extrudeWalls(index) to prepare extrude internal wall.

    • Extract Result: Use getWallMeshes() to retrieve the wall meshes.

  5. Add Floors:

    • call addFloors(index) to add floors, number of floor is deduced from building height (always near 3 meters).

    • Extract Result: Use getWallMeshes() to retrieve the floor meshes.

  6. Generate and Process Roof (optional):

    • If the roof option is enabled, call generateRoof(index), followed by transformRoof(index), extrudeRoofWalls(index), and mergeWallRoof(index).

    • Extract Result: Use getWallMeshes() for the combined result.

  7. Merge All Meshes (optional):

    • Use mergeAllMeshes() to combine all meshes into a final model.

    • Extract Result: Use getWallMeshes()[0] to retrieve the final merged meshes.

    • Result: Result is written in MSH format.

  8. 3D Meshing (optional):

    • If Volume is enabled, call meshing3D(0) to perform 3D meshing.

    • Result: result is written in VTU format.

3. Important Notes

  • createBuildings() : This method creates and merges every surface mesh with roof if the roof option is activated.

  • Result : Every result are written in a result file created if needed.

  • Debug: Debug option will write a file at every step of the building creation in a result/intermediate folder created if needed.

4. Example main Function

Here’s a streamlined example of how to use the MultipleBuilding class, highlighting the importance of the order in which methods are called and how to extract results.

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h> // Kernel is needed because of the CGAL function used
#include <ktirio/geom/buildinglod1/multiplebuilding.hpp>



namespace Feel::Ktirio::Geom {
    using Kernel = CGAL::Exact_predicates_inexact_constructions_kernel;
    using namespace Buildinglod1;
}

int main() {

    using namespace Feel::Ktirio::Geom;
    bool debug=true;
    bool roof=true;
    bool Union=false; // Union will lose every marker else than buildindId
    bool Volume=false;
    MultipleBuilding<Kernel> building(debug, roof, Union,Volume);

    std::string json = "../..data/buildinglod1/gis.json";
    building.loadFromJsonGis(json); // or loadFromJsonDat(json); depending of the inputted data
    for (size_t i = 0; i < building.getPolygons().size(); ++i)
    {
        // Correct method order
         //building.getBaseMeshes(); // Extract base meshes
        building.triangulateBasePolygon(i);

         //building.getBaseMeshes(); // Extract extruded base meshes
        building.extrudeBasePolygon(i);


        // building.getWallMeshes(); // Extract wall meshes
        building.extrudeWalls(i);


        //Optionnal if roof isn't generated
         //building.getWallMeshes(); // Extract floor meshes
        building.addFloors(i);


        if (roof) // Optional: Generate roof if needed
        {

             //building.getRoofMeshes(); // Extract roof meshes
            building.generateRoof(i);



             //building.getRoofMeshes(); // Extract transformed roof meshes
            building.transformRoof(i);


             //building.getRoofWallMeshes(); // Extract extruded roof meshes
            building.extrudeRoofWalls(i);

             //building.getWallMeshes(); // Exctract merged mesh
            building.mergeWallRoof(i);

        }
    }

    //Optional: Merge all building in one mesh and write result
     //building.getWallMeshes()[0]; // Extract final merged meshes
    building.mergeAllMeshes();


    // Optional: Create Volume Mesh if asked of the building index ( 0 after mergeAllMeshes is all building ) and write result in vtu format
    if(Volume)
      building.meshing3D(0);

    return 0;
}

Next: Multiple Building Documentation



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