GeometryReader.ShapeInstances is empty if the optional RepresentationIdentifier and RepresentationType values of IfcShapeRepresentation are not filled by the export software.

[andreinovikovsiemens]

According to IFC spec https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcRepresentation.htm IfcRepresentation.RepresentationIdentifier and IfcRepresentation.RepresentationType are optional. Not all exporting software fill RepresentationIdentifier and RepresentationType properties which leads to xbim reports model contains no shape instances in models from such software

To reporduce the issue

1. Open attached project in visual studio. XBimGeometryMissing.zip
2. Add path of attached IFC file to the launch settings command-line arguments wall.zip
3. Build and run console application

Current output:

Hello xbim!
shape instances: 0

Expected output:

Hello xbim!
shape instances: 1

If RepresentationIdentifier and RepresentationType are filled in, xbim reports the ShapeInstances count is 1. wall_orig.zip

I assume a possible reason may be related to changes in this commit 54cc1bf

---

Here is source code of example project just in case

using Xbim.Common.Geometry;
using Xbim.Ifc;
using Xbim.ModelGeometry.Scene;

namespace XBimGeometryMissing
{

    public static class Program
    {
        public static int Main(string[] args)
        {

            Console.WriteLine("Hello xbim!");

            using (IfcStore store = IfcStore.Open(args[0]))
            {
                var modelContext = new Xbim3DModelContext(store);
                modelContext.CreateContext();


                using (IGeometryStoreReader reader = store.GeometryStore.BeginRead())
                {
                    Console.WriteLine("shape instances: " + reader.ShapeInstances.Count());
                }
            }

            return 0;
        }
    }
}

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net9.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

    <ItemGroup>
        <PackageReference Include="System.Configuration.ConfigurationManager" Version="10.0.9" />
        <PackageReference Include="Xbim.Essentials" Version="6.0.587" />
        <PackageReference Include="Xbim.Geometry" Version="5.1.820" />
    </ItemGroup>

</Project>

[andyward]

While RepresentationType and RepresentationIdentifier may be optional in IfcRepresentation there are Formal Propositions on the derived classes that require the values to be populated. e.g see IfcShapeRepresentation.HasRepresentationType

If you put the model through the free IFC validator service at https://validate.buildingsmart.org/ this is what you get:

I guess it would be possible to change the engine to me more permissive and infer the representation type from the ShapeRepresentation.Items.

Did Revit 2026 really export the model like this or was it manipulated after export?

[andreinovikovsiemens]

@andyward Thank you for reply!
This file was manually edited after export, to reproduce the issue with real file that was exported from DATAflor BIMMANAGER 23.0

Sure this file have IFC schema violations. But shapes is still presented in file and can be rendered. Other software can render this file and
xbim xplorer have no issues to render such file. wall4.

I assume xbim xplorer uses older version on xbim.geometry which is not that strict to this particular IFC schema violation.

Is there a particular reason to report 0 ShapeInstances for files that violates IFC schema in such way even if shapes is presented in the file?