IFC_gbXML_Convert.py

# Import necessary python libraries e.g. IfcOpenShell, PythonOCC and MiniDom
import ifcopenshell.geom
import OCC.Core.BRep
import OCC.Core.TopExp
import OCC.Core.TopoDS
import OCC.Core.TopAbs
import OCC.Core.ProjLib
import OCC.Core.BRepTools
import datetime
import time
from xml.dom import minidom

# Use IfcOpenShell and OPENCASCADE to convert implicit geometry into explicit geometry
# Each Face consists of Wires, which consists of Edges, which has Vertices
FACE, WIRE, EDGE, VERTEX = OCC.Core.TopAbs.TopAbs_FACE, OCC.Core.TopAbs.TopAbs_WIRE, OCC.Core.TopAbs.TopAbs_EDGE, \
                           OCC.Core.TopAbs.TopAbs_VERTEX

settings = ifcopenshell.geom.settings()
settings.set(settings.USE_PYTHON_OPENCASCADE, True)


def sub(shape, ty):
    F = {
        OCC.Core.TopAbs.TopAbs_FACE: OCC.Core.TopoDS.topods_Face,
        OCC.Core.TopAbs.TopAbs_WIRE: OCC.Core.TopoDS.topods_Wire,
        OCC.Core.TopAbs.TopAbs_EDGE: OCC.Core.TopoDS.topods_Edge,
        OCC.Core.TopAbs.TopAbs_VERTEX: OCC.Core.TopoDS.topods_Vertex,
    }[ty]
    exp = OCC.Core.TopExp.TopExp_Explorer(shape, ty)
    while exp.More():
        face = F(exp.Current())
        yield face
        exp.Next()


def ring(wire, face):
    def vertices():
        exp = OCC.Core.BRepTools.BRepTools_WireExplorer(wire, face)
        while exp.More():
            yield exp.CurrentVertex()
            exp.Next()
        yield exp.CurrentVertex()

    return list(map(lambda p: (p.X(), p.Y(), p.Z()), map(OCC.Core.BRep.BRep_Tool.Pnt, vertices())))


# Face to vertices
def get_vertices(shape):
    for face in sub(shape, FACE):
        for idx, wire in enumerate(sub(face, WIRE)):
            vertices = ring(wire, face)

            if idx > 0:
                vertices.reverse()
            return vertices


# Align the gbXML input according to the predefined official gbXML schema
def fix_xml_cmps(a):
    return 'campus' + a.replace('$', '').replace(':', '').replace(' ', '').replace('(', '').replace(')', '')


def fix_xml_bldng(a):
    return 'building' + a.replace('$', '').replace(':', '').replace(' ', '').replace('(', '').replace(')', '')


def fix_xml_stry(a):
    return 'storey' + a.replace('$', '').replace(':', '').replace(' ', '').replace('(', '').replace(')', '')


def fix_xml_spc(a):
    return 'space' + a.replace('$', '').replace(':', '').replace(' ', '').replace('(', '').replace(')', '')


def fix_xml_id(a):
    return 'id' + a.replace('$', '').replace(':', '').replace(' ', '').replace('(', '').replace(')', '')


def fix_xml_name(a):
    return 'object' + a.replace('$', '').replace(':', '').replace(' ', '').replace('(', '').replace(')', '')


def fix_xml_cons(a):
    return 'construct' + a.replace('$', '').replace(':', '').replace(' ', '').replace('(', '').replace(')', '')


def fix_xml_layer(a):
    return 'lyr' + a.replace('$', '').replace(':', '').replace(' ', '').replace('(', '').replace(')', '')

# Access the specific IFC file; external directory: (r"C:/Users/s136146/Desktop/StoreysWindowsMaterialsFacade.ifc")
ifc_file = ifcopenshell.open('Pilot project 5.ifc')

# Create the XML root by making use of MiniDom
root = minidom.Document()

# Create the 'gbXML' element and append it to the Root of the document
gbxml = root.createElement('gbXML')
root.appendChild(gbxml)

# Create attributes for the 'gbXML' element
gbxml.setAttribute('xmlns', 'http://www.gbxml.org/schema')
gbxml.setAttribute('temperatureUnit', 'C')
gbxml.setAttribute('lengthUnit', 'Meters')
gbxml.setAttribute('areaUnit', 'SquareMeters')
gbxml.setAttribute('volumeUnit', 'CubicMeters')
gbxml.setAttribute('useSIUnitsForResults', 'true')
gbxml.setAttribute('version', '0.37')

# Create a dictionary to store all gbXML element Id's
dict_id = {}

# Specify the 'Campus' element of the gbXML schema; making use of IFC entity 'IfcSite'
# This element is added as child to the earlier created 'gbXML' element
site = ifc_file.by_type('IfcSite')
for element in site:
    campus = root.createElement('Campus')
    campus.setAttribute('id', fix_xml_cmps(element.GlobalId))
    gbxml.appendChild(campus)

    dict_id[fix_xml_cmps(element.GlobalId)] = campus

    # Specify the 'Location' element of the gbXML schema; making use of IFC entities 'IfcSite' and 'IfcPostalAddress'
    # This new element is added as child to the earlier created 'Campus' element
    location = root.createElement('Location')
    campus.appendChild(location)

    longitude = root.createElement('Longitude')
    longitudeValue = str(element.RefLongitude[0])
    longitude.appendChild(root.createTextNode(longitudeValue))
    location.appendChild(longitude)

    latitude = root.createElement('Latitude')
    latitudeValue = str(element.RefLatitude[0])
    latitude.appendChild(root.createTextNode(latitudeValue))
    location.appendChild(latitude)

    elevation = root.createElement('Elevation')
    elevation.appendChild(root.createTextNode(str(element.RefElevation)))
    location.appendChild(elevation)

address = ifc_file.by_type('IfcPostalAddress')
for element in address:
    zipcode = root.createElement('ZipcodeOrPostalCode')
    zipcode.appendChild(root.createTextNode(element.PostalCode))
    location.appendChild(zipcode)

    name = root.createElement('Name')
    name.appendChild(root.createTextNode(element.Region + ', ' + element.Country))
    location.appendChild(name)

# Specify the 'Building' element of the gbXML schema; making use of IFC entity 'IfcBuilding'
# This new element is added as child to the earlier created 'Campus' element
buildings = ifc_file.by_type('IfcBuilding')
for element in buildings:
    building = root.createElement('Building')
    building.setAttribute('id', fix_xml_bldng(element.GlobalId))
    building.setAttribute('buildingType', "Unknown")
    campus.appendChild(building)

    dict_id[fix_xml_bldng(element.GlobalId)] = building

for element in address:
    streetAddress = root.createElement('StreetAddress')
    streetAddress.appendChild(root.createTextNode(element.Region + ', ' + element.Country))
    building.appendChild(streetAddress)

# Specify the 'BuildingStorey' element of the gbXML schema; making use of IFC entity 'IfcBuildingStorey'
# This new element is added as child to the earlier created 'Building' element
storeys = ifc_file.by_type('IfcBuildingStorey')
storey_name = 1
for element in storeys:
    buildingStorey = root.createElement('BuildingStorey')
    buildingStorey.setAttribute('id', fix_xml_stry(element.GlobalId))
    building.appendChild(buildingStorey)

    dict_id[fix_xml_stry(element.GlobalId)] = buildingStorey

    name = root.createElement('Name')
    name.appendChild(root.createTextNode('Storey_%d' % storey_name))
    storey_name = storey_name + 1
    buildingStorey.appendChild(name)

    level = root.createElement('Level')
    level.appendChild(root.createTextNode(str(element.Elevation)))
    buildingStorey.appendChild(level)

# Specify the 'Space' element of the gbXML schema; making use of IFC entity 'IfcSpace'
# This new element is added as child to the earlier created 'Building' element
spaces = ifc_file.by_type('IfcSpace')
space_name = 1
for s in spaces:
    space = root.createElement('Space')
    space.setAttribute('id', fix_xml_spc(s.GlobalId))
    building.appendChild(space)

    dict_id[fix_xml_spc(s.GlobalId)] = space

    # Refer to the relating 'BuildingStorey' GUID by iterating through IFC entities
    space.setAttribute('buildingStoreyIdRef', fix_xml_stry(s.Decomposes[0].RelatingObject.GlobalId))

    area = root.createElement('Area')
    volume = root.createElement('Volume')

    properties = s.IsDefinedBy
    for r in properties:
        if r.is_a('IfcRelDefinesByProperties'):
            if r.RelatingPropertyDefinition.is_a('IfcPropertySet'):
                for p in r.RelatingPropertyDefinition.HasProperties:
                    if p.Name == 'Area':
                        valueArea = p.NominalValue.wrappedValue
                        area.appendChild(root.createTextNode(str(valueArea)))
                        space.appendChild(area)
                    if p.Name == 'Volume':
                        valueVolume = p.NominalValue.wrappedValue
                        volume.appendChild(root.createTextNode(str(valueVolume)))
                        space.appendChild(volume)

    name = root.createElement('Name')
    name.appendChild(root.createTextNode('Space_%d' % space_name))
    space_name = space_name + 1
    space.appendChild(name)

    # Specify the 'SpaceBoundary' element of the gbXML schema; making use of IFC entity 'IfcSpace'
    # This new element is added as child to the earlier created 'Space' element
    boundaries = s.BoundedBy
    for element in boundaries:

        # Make sure a 'SpaceBoundary' is representing an actual element
        if element.RelatedBuildingElement == None:
            continue

        # Specify the 'IfcCurveBoundedPlane' entity which represents the geometry
        boundaryGeom = element.ConnectionGeometry.SurfaceOnRelatingElement

        if boundaryGeom.is_a('IfcCurveBoundedPlane') and boundaryGeom.InnerBoundaries is None:
            boundaryGeom.InnerBoundaries = ()

        print(boundaryGeom)

        # Use IfcOpenShell and OPENCASCADE to attach geometry to the specified IFC entity
        space_boundary_shape = ifcopenshell.geom.create_shape(settings, boundaryGeom)

        # Create 'SpaceBoundary' elements for the following building elements
        if element.RelatedBuildingElement.is_a('IfcCovering') or element.RelatedBuildingElement.is_a('IfcSlab') or \
                element.RelatedBuildingElement.is_a('IfcWall') or element.RelatedBuildingElement.is_a('IfcRoof'):

            spaceBoundary = root.createElement('SpaceBoundary')
            spaceBoundary.setAttribute('isSecondLevelBoundary', "true")

            # Refer to the relating 'SpaceBoundary' GUID by iterating through IFC entities
            spaceBoundary.setAttribute('surfaceIdRef', fix_xml_id(element.GlobalId))

            space.appendChild(spaceBoundary)

            planarGeometry = root.createElement('PlanarGeometry')
            spaceBoundary.appendChild(planarGeometry)

            # Specify the 'PolyLoop' element which contains 4 'CartesianPoint' elements with each
            # 3 explicit 'Coordinate' elements. Note: if geometry is not attached to the 'SpaceBoundary' element, the
            # relationship between 'Space' and 'Building' elements is handled only on a logical level. If geometry is
            # attached, it is given within the local coordinate systems of the 'Space' and (if given in addition) of the
            # 'Building' element.

            # Z-coordinates are extracted by iterating through IFC entities to the 'IfcCartesianPoint' of the
            # related 'IfcBuildingStorey'
            print('SpaceBoundary')

            new_z = element.RelatingSpace.ObjectPlacement.PlacementRelTo.RelativePlacement.Location.Coordinates[2]
            new_z = new_z

            polyLoop = root.createElement('PolyLoop')

            for v in get_vertices(space_boundary_shape):
                x, y, z = v
                z = z + new_z
                print(x, y, z)

                point = root.createElement('CartesianPoint')

                for c in x, y, z:
                    coord = root.createElement('Coordinate')
                    coord.appendChild(root.createTextNode(str(c)))
                    point.appendChild(coord)

                polyLoop.appendChild(point)

            planarGeometry.appendChild(polyLoop)

# Specify the 'Surface' element of the gbXML schema; making use of IFC entity 'IfcRelSpaceBoundary'
# This new element is added as child to the earlier created 'Campus' element
boundaries = ifc_file.by_type('IfcRelSpaceBoundary')
opening_id = 1
for element in boundaries:
    # Make sure a 'SpaceBoundary' is representing an actual element
    if element.RelatedBuildingElement == None:
        continue

    # Specify the 'IfcCurveBoundedPlane' entity which represents the geometry
    if element.ConnectionGeometry.SurfaceOnRelatingElement == None:
        continue

    surfaceGeom = element.ConnectionGeometry.SurfaceOnRelatingElement

    if surfaceGeom.is_a('IfcCurveBoundedPlane') and surfaceGeom.InnerBoundaries is None:
        surfaceGeom.InnerBoundaries = ()

    print(surfaceGeom)

    space_boundary_shape = ifcopenshell.geom.create_shape(settings, surfaceGeom)

    # Specify each 'Surface' element and set 'SurfaceType' attributes
    if element.RelatedBuildingElement.is_a('IfcCovering') or element.RelatedBuildingElement.is_a('IfcSlab') or element.\
            RelatedBuildingElement.is_a('IfcWall') or element.RelatedBuildingElement.is_a('IfcRoof'):

        surface = root.createElement('Surface')
        surface.setAttribute('id', fix_xml_id(element.GlobalId))
        dict_id[fix_xml_id(element.GlobalId)] = surface

        if element.RelatedBuildingElement.is_a('IfcCovering'):
            surface.setAttribute('surfaceType', 'Ceiling')

        if element.RelatedBuildingElement.is_a('IfcSlab'):
            surface.setAttribute('surfaceType', 'InteriorFloor')

        if element.RelatedBuildingElement.is_a('IfcWall') and element.\
                InternalOrExternalBoundary == 'EXTERNAL':
            surface.setAttribute('surfaceType', 'ExteriorWall')

        if element.RelatedBuildingElement.is_a('IfcWall') and element.\
                InternalOrExternalBoundary == 'INTERNAL':
            surface.setAttribute('surfaceType', 'InteriorWall')

        if element.RelatedBuildingElement.is_a('IfcRoof'):
            surface.setAttribute('surfaceType', 'Roof')

        # Refer to the relating 'IfcRelAssociatesMaterial' GUID by iterating through IFC entities
        surface.setAttribute('constructionIdRef', fix_xml_cons(element.RelatedBuildingElement.
                                                               HasAssociations[0].GlobalId))

        name = root.createElement('Name')
        name.appendChild(root.createTextNode(fix_xml_name(element.GlobalId)))

        surface.appendChild(name)

        adjacentSpaceId = root.createElement('AdjacentSpaceId')

        # Refer to the relating 'Space' GUID by iterating through IFC entities
        adjacentSpaceId.setAttribute('spaceIdRef', fix_xml_spc(element.RelatingSpace.GlobalId))
        surface.appendChild(adjacentSpaceId)

        planarGeometry = root.createElement('PlanarGeometry')
        surface.appendChild(planarGeometry)

        # Specify the 'PolyLoop' element which contains 4 'CartesianPoint' elements with each
        # 3 explicit 'Coordinate' elements. Note: if geometry is not attached to the 'SpaceBoundary' element, the
        # relationship between 'Space' and 'Building' elements is handled only on a logical level. If geometry is
        # attached, it is given within the local coordinate systems of the 'Space' and (if given in addition) of the
        # 'Building' element.

        # Z-coordinates are extracted by iterating through IFC entities to the 'IfcCartesianPoint' of the
        # related 'IfcBuildingStorey'
        print("Surface")

        new_z = element.RelatingSpace.ObjectPlacement.PlacementRelTo.RelativePlacement.Location.Coordinates[2]
        new_z = new_z

        polyLoop = root.createElement('PolyLoop')

        for v in get_vertices(space_boundary_shape):
            x, y, z = v
            z = z + new_z
            print(x, y, z)

            point = root.createElement('CartesianPoint')

            for c in x, y, z:
                coord = root.createElement('Coordinate')
                coord.appendChild(root.createTextNode(str(c)))
                point.appendChild(coord)

            polyLoop.appendChild(point)

        planarGeometry.appendChild(polyLoop)

        objectId = root.createElement('CADObjectId')
        objectId.appendChild(root.createTextNode(fix_xml_name(element.GlobalId)))
        surface.appendChild(objectId)

        campus.appendChild(surface)

    if element.RelatedBuildingElement.is_a('IfcWindow'):
        opening = root.createElement('Opening')

        # Refer to the relating 'IfcWindow' GUID by iterating through IFC entities
        opening.setAttribute('windowTypeIdRef', fix_xml_id(element.RelatedBuildingElement.GlobalId))
        opening.setAttribute('openingType', 'OperableWindow')

        opening.setAttribute('id', 'Opening%d' % opening_id)
        opening_id = opening_id + 1

        # If the building element is an 'IfcWindow' the gbXML element 'Opening' is added
        print('Opening')
        planarGeometry = root.createElement('PlanarGeometry')
        opening.appendChild(planarGeometry)

        # Specify the 'PolyLoop' element which contains 4 'CartesianPoint' elements with each
        # 3 explicit 'Coordinate' elements. Note: if geometry is not attached to the 'SpaceBoundary' element, the
        # relationship between 'Space' and 'Building' elements is handled only on a logical level. If geometry is
        # attached, it is given within the local coordinate systems of the 'Space' and (if given in addition) of the
        # 'Building' element.

        # Z-coordinates are extracted by iterating through IFC entities to the 'IfcCartesianPoint' of the
        # related 'IfcBuildingStorey'
        polyLoop = root.createElement('PolyLoop')

        new_z = element.RelatingSpace.ObjectPlacement.PlacementRelTo.RelativePlacement.Location.Coordinates[2]
        new_z = new_z

        for v in get_vertices(space_boundary_shape):
            x, y, z = v
            z = z + new_z
            print(x, y, z)

            point = root.createElement('CartesianPoint')

            for c in x, y, z:
                coord = root.createElement('Coordinate')
                coord.appendChild(root.createTextNode(str(c)))
                point.appendChild(coord)

            polyLoop.appendChild(point)

        planarGeometry.appendChild(polyLoop)

        name = root.createElement('Name')
        name.appendChild(root.createTextNode(fix_xml_name(element.RelatedBuildingElement.Name)))
        opening.appendChild(name)

        objectId = root.createElement('CADObjectId')
        objectId.appendChild(root.createTextNode(fix_xml_name(element.RelatedBuildingElement.Name)))
        opening.appendChild(objectId)

        surface.appendChild(opening)

    else:
        continue

# Specify the 'WindowType' element of the gbXML schema; making use of IFC entity 'IfcWindow'
# This new element is added as child to the earlier created 'gbXML' element
windows = ifc_file.by_type('IfcWindow')
for element in windows:
    window = root.createElement('WindowType')
    window.setAttribute('id', fix_xml_id(element.GlobalId))
    gbxml.appendChild(window)

    dict_id[fix_xml_id(element.GlobalId)] = window

    name = root.createElement('Name')
    name.appendChild(root.createTextNode(fix_xml_name(element.Name)))
    window.appendChild(name)

    description = root.createElement('Description')
    description.appendChild(root.createTextNode(fix_xml_name(element.Name)))
    window.appendChild(description)

    # Specify analytical properties of the 'IfcWindow' by iterating through IFC entities
    analyticValue = element.IsDefinedBy

    u_value = root.createElement('U-value')
    for r in analyticValue:
        if r.is_a("IfcRelDefinesByProperties"):
            if r.RelatingPropertyDefinition.is_a('IfcPropertySet'):
                for p in r.RelatingPropertyDefinition.HasProperties:
                    if p.Name == 'ThermalTransmittance':
                        valueU = p.NominalValue.wrappedValue
                        u_value.setAttribute('unit', 'WPerSquareMeterK')
                        u_value.appendChild(root.createTextNode(str(valueU)))
                        window.appendChild(u_value)

    solarHeat = root.createElement('SolarHeatGainCoeff')
    visualLight = root.createElement('Transmittance')
    for r in analyticValue:
        if r.is_a('IfcRelDefinesByType'):
            if r.RelatingType.is_a('IfcWindowStyle'):
                for p in r.RelatingType.HasPropertySets:
                    if p.Name == 'Analytical Properties(Type)':
                        for t in p.HasProperties:
                            if t.Name == 'Solar Heat Gain Coefficient':
                                valueSolar = t.NominalValue.wrappedValue
                                solarHeat.setAttribute('unit', 'Fraction')
                                solarHeat.appendChild(root.createTextNode(str(valueSolar)))
                                window.appendChild(solarHeat)

                            if t.Name == 'Visual Light Transmittance':
                                valueLight = t.NominalValue.wrappedValue
                                visualLight.setAttribute('unit', 'Fraction')
                                visualLight.setAttribute('type', 'Visible')
                                visualLight.appendChild(root.createTextNode(str(valueLight)))
                                window.appendChild(visualLight)

# Specify the 'Construction' element of the gbXML schema; making use of IFC entity 'IfcRelSpaceBoundary'
# This new element is added as child to the earlier created 'gbXML' element
listCon = []

for element in boundaries:
    # Make sure a 'SpaceBoundary' is representing an actual element
    if element.RelatedBuildingElement is None:
        continue

    if element.RelatedBuildingElement.is_a('IfcCovering') or element.RelatedBuildingElement.is_a('IfcSlab') or element.\
            RelatedBuildingElement.is_a('IfcWall') or element.RelatedBuildingElement.is_a('IfcRoof'):

        # Refer to the relating 'IfcRelAssociatesMaterial' GUID by iterating through IFC entities
        constructions = element.RelatedBuildingElement.HasAssociations[0].GlobalId

        # Make use of a list to make sure no same 'Construction' elements are added twice
        if constructions not in listCon:
            listCon.append(constructions)

            construction = root.createElement('Construction')
            construction.setAttribute('id', fix_xml_cons(element.RelatedBuildingElement.HasAssociations[0].GlobalId))
            dict_id[fix_xml_cons(element.RelatedBuildingElement.HasAssociations[0].GlobalId)] = construction

            # Specify analytical properties of the 'Construction' element by iterating through IFC entities
            analyticValue = element.RelatedBuildingElement.IsDefinedBy

            u_value = root.createElement('U-value')
            for r in analyticValue:
                if r.is_a('IfcRelDefinesByProperties'):
                    if r.RelatingPropertyDefinition.is_a('IfcPropertySet'):
                        for p in r.RelatingPropertyDefinition.HasProperties:
                            if element.RelatedBuildingElement.is_a("IfcWall"):
                                if p.Name == 'ThermalTransmittance':
                                    valueU = p.NominalValue.wrappedValue
                                    u_value.setAttribute('unit', 'WPerSquareMeterK')
                                    u_value.appendChild(root.createTextNode(str(valueU)))
                                    construction.appendChild(u_value)

                            if p.Name == 'Heat Transfer Coefficient (U)':
                                valueU = p.NominalValue.wrappedValue
                                u_value.setAttribute('unit', 'WPerSquareMeterK')
                                u_value.appendChild(root.createTextNode(str(valueU)))
                                construction.appendChild(u_value)

            absorptance = root.createElement('Absorptance')
            for r in analyticValue:
                if r.is_a('IfcRelDefinesByProperties'):
                    if r.RelatingPropertyDefinition.is_a('IfcPropertySet'):
                        for p in r.RelatingPropertyDefinition.HasProperties:
                            if p.Name == 'Absorptance':
                                valueAb = p.NominalValue.wrappedValue
                                absorptance.setAttribute('unit', 'Fraction')
                                absorptance.setAttribute('type', 'ExtIR')
                                absorptance.appendChild(root.createTextNode(str(valueAb)))
                                construction.appendChild(absorptance)

            # Refer to the relating 'IfcRelAssociatesMaterial' GUID by iterating through IFC entities
            layerId = fix_xml_layer(element.RelatedBuildingElement.HasAssociations[0].GlobalId)

            layer_id = root.createElement('LayerId')
            layer_id.setAttribute('layerIdRef', layerId)
            construction.appendChild(layer_id)

            # Refer to the relating 'IfcMaterialLayerSet' name by iterating through IFC entities
            name = root.createElement('Name')
            name.appendChild(root.createTextNode(element.RelatedBuildingElement.HasAssociations[0].RelatingMaterial.
                                                 ForLayerSet.LayerSetName))
            construction.appendChild(name)

            gbxml.appendChild(construction)

    else:
        continue

# Specify the 'Layer' element of the gbXML schema; making use of IFC entity 'IfcBuildingElement'
# This new element is added as child to the earlier created 'gbXML' element
buildingElements = ifc_file.by_type('IfcBuildingElement')
for element in buildingElements:
    if element.is_a('IfcWall') or element.is_a('IfcCovering') or element.is_a('IfcSlab') or element.is_a('IfcRoof'):

        # Try and catch an Element that is just an Aggregate
        if element.IsDecomposedBy:
            continue
        # Refer to the relating 'IfcRelAssociatesMaterial' GUID by iterating through IFC entities
        layerId = fix_xml_layer(element.HasAssociations[0].GlobalId)

        layer = root.createElement('Layer')
        layer.setAttribute('id', layerId)

        dict_id[layerId] = layer

        # Specify the 'IfcMaterialLayer' entity and iterate to each 'IfcMaterial' entity
        if not element.HasAssociations[0].RelatingMaterial.is_a('IfcMaterialLayerSetUsage'):
            continue
        materials = element.HasAssociations[0].RelatingMaterial.ForLayerSet.MaterialLayers
        for l in materials:
            material_id = root.createElement('MaterialId')
            material_id.setAttribute('materialIdRef', "mat_%d" % l.Material.id())
            layer.appendChild(material_id)

            dict_id["mat_%d" % l.Material.id()] = layer

            gbxml.appendChild(layer)

    else:
        continue

# Specify the 'Material' element of the gbXML schema; making use of IFC entity 'IfcBuildingElement'
# This new element is added as child to the earlier created 'gbXML' element
listMat = []

for element in buildingElements:
    if element.is_a('IfcWall') or element.is_a("IfcSlab") or element.is_a('IfcCovering') or element.is_a('IfcRoof'):

        # Try and catch an Element that is just an Aggregate
        if element.IsDecomposedBy:
            continue
        if not element.HasAssociations[0].RelatingMaterial.is_a('IfcMaterialLayerSetUsage'):
            continue
        materials = element.HasAssociations[0].RelatingMaterial.ForLayerSet.MaterialLayers

        for l in materials:
            item = l.Material.id()

            # Make use of a list to make sure no same 'Materials' elements are added twice
            if item not in listMat:
                listMat.append(item)

                material = root.createElement('Material')
                material.setAttribute('id', "mat_%d" % l.Material.id())
                dict_id["mat_%d" % l.Material.id()] = material

                name = root.createElement('Name')
                name.appendChild(root.createTextNode(l.Material.Name))
                material.appendChild(name)

                thickness = root.createElement('Thickness')
                thickness.setAttribute('unit', 'Meters')
                valueT = l.LayerThickness
                thickness.appendChild(root.createTextNode((str(valueT))))
                material.appendChild(thickness)

                rValue = root.createElement('R-value')
                rValue.setAttribute('unit', 'SquareMeterKPerW')

                # Analytical properties of the Material entity can be found directly
                for material_property in l.Material.HasProperties:
                    if material_property.Name == 'Pset_MaterialEnergy':
                        for pset_material_energy in material_property.Properties:
                            if pset_material_energy.Name == 'ThermalConductivityTemperatureDerivative':
                                valueR = pset_material_energy.NominalValue.wrappedValue
                                rValue.setAttribute('unit', 'SquareMeterKPerW')
                                rValue.appendChild(root.createTextNode(str(valueR)))
                                material.appendChild(rValue)

                                gbxml.appendChild(material)

                # Specify analytical properties of the 'Material' element by iterating through IFC entities
                thermalResistance = element.IsDefinedBy
                for r in thermalResistance:
                    if r.is_a('IfcRelDefinesByType'):
                        if r.RelatingType.is_a('IfcWallType'):
                            for p in r.RelatingType.HasPropertySets:
                                if p.Name == 'Analytical Properties(Type)':
                                    for t in p.HasProperties:
                                        if t.Name == 'Heat Transfer Coefficient (U)':
                                            valueU = t.NominalValue.wrappedValue
                                            valueR = valueT / valueU
                                            rValue.appendChild(root.createTextNode(str(valueR)))
                                            material.appendChild(rValue)

                                            gbxml.appendChild(material)

                    if r.is_a('IfcRelDefinesByProperties'):
                        if r.RelatingPropertyDefinition.is_a('IfcPropertySet'):
                            for p in r.RelatingPropertyDefinition.HasProperties:
                                if p.Name == 'Heat Transfer Coefficient (U)':
                                    valueU = p.NominalValue.wrappedValue
                                    valueR = valueT / valueU
                                    rValue.setAttribute('unit', 'SquareMeterKPerW')
                                    rValue.appendChild(root.createTextNode(str(valueR)))
                                    material.appendChild(rValue)

                                    gbxml.appendChild(material)

                    if element.is_a('IfcCovering'):
                        if r.is_a('IfcRelDefinesByProperties'):
                            if r.RelatingType.is_a('IfcPropertySet'):
                                for p in r.RelatingType.HasPropertySets:
                                    if p.Name == 'Analytical Properties(Type)':
                                        for t in p.HasProperties:
                                            if t.Name == 'Heat Transfer Coefficient (U)':
                                                valueU = t.NominalValue.wrappedValue
                                                valueR = valueT / valueU
                                                rValue.setAttribute('unit', 'SquareMeterKPerW')
                                                rValue.appendChild(root.createTextNode(str(valueR)))
                                                material.appendChild(rValue)

                                                gbxml.appendChild(material)

    else:
        continue

# Specify the 'DocumentHistory' element of the gbXML schema; making use of IFC entity 'IfcApplication' and 'IfcPerson'
# This new element is added as child to the earlier created 'gbXML' element
programInfo = ifc_file.by_type('IfcApplication')
docHistory = root.createElement('DocumentHistory')
for element in programInfo:
    program = root.createElement('ProgramInfo')
    program.setAttribute('id', element.ApplicationIdentifier)
    docHistory.appendChild(program)

    company = root.createElement('CompanyName')
    company.appendChild(root.createTextNode(element.ApplicationDeveloper.Name))
    program.appendChild(company)

    product = root.createElement('ProductName')
    product.appendChild(root.createTextNode(element.ApplicationFullName))
    program.appendChild(product)

    version = root.createElement('Version')
    version.appendChild(root.createTextNode(element.Version))
    program.appendChild(version)

personInfo = ifc_file.by_type('IfcPerson')
for element in personInfo:
    created = root.createElement('CreatedBy')
    created.setAttribute('personId', element.GivenName)

for element in programInfo:
    created.setAttribute('programId', element.ApplicationIdentifier)

    today = datetime.date.today()
    created.setAttribute('date', today.strftime('%Y-%m-%dT') + time.strftime('%H:%M:%S'))
    docHistory.appendChild(created)

for element in personInfo:
    person = root.createElement('PersonInfo')
    person.setAttribute('id', element.GivenName)
    docHistory.appendChild(person)

gbxml.appendChild(docHistory)

# Create a new XML file and write all created elements to it
save_path_file = "New_Exported_gbXML.xml"

root.writexml( open(save_path_file, "w"),
               indent="  ",
               addindent="  ",
               newl='\n')