dn9090 / xbimgltf

Export IFC geometry to gltf and related data to json

XbimGltf

Requirements

Microsoft Visual C++ Redistributable 2015, 2017, 2019

Microsoft .NET Framework 4.7.2

Quick Start

Before you can use the GLTF builder you need to convert the original IFC file to a meshed xBIM file:

IfcStore.ModelProviderFactory.UseHeuristicModelProvider();

using(var model = IfcStore.Open("Files/House.ifc"))
{
	var context = new Xbim3DModelContext(model);
	context.CreateContext(null, false);
	model.SaveAs("Files/House.xBIM");
}

Create a GLTF file with the new builder

using(var model = IfcStore.Open("Files/House.xBIM"))
{
	var builder = new XbimGltfBuilder(model);
	builder.Build().SaveAs("Files/House.gltf");
}

Please notice that new builder uses other default configurations than the old one.

Create a GLTF file with the compability API

The compatibility API matches the original builder API but uses the new builder under the hood. Note that the original builder and the compatibility API is marked as Obsolete.

using(var model = IfcStore.Open("Files/House.xBIM"))
{
	var builder = new Builder();
	builder.BuildInstancedScene(model, XbimMatrix3D.Identity).SaveAs("Files/House.gltf");
}

Merge Primitives

There are two different options to create the nodes from the IFC file. The first one creates a hierarchy with separate child nodes for each mesh primitive:

using(var model = IfcStore.Open("Files/House.xBIM"))
{
	var builder = new Builder();
	builder.MergePrimitives = false; // This is the default value.
	builder.BuildInstancedScene(model, XbimMatrix3D.Identity).SaveAs("Files/House.gltf");
}

The resulting hierarchy should look similiar to this:

Root
| - Wall #10
| | - Shape #1001
| - Door #20
| | - Shape #2001
| - Window #30
| | - Shape #3001
| | - Shape #3002
| - Wall #40
| | - Shape #4001

If MergePrimitives is set to true the hierarchy will be flat:

Root
| - Wall #10
| - Door #20
| - Window #30
| - Wall #40

In the flat hierarchy a mesh can consist of multiple primitives.

Tests

The ensure that the rework works as expected the ``Xbim.GLTF.IO.Tests` directory contains compatibility tests of all implementations. The compatibility is tested by comparing the output files with the output file of original implementation.

The tests are using Xunit and can be run with:

dotnet test

Benchmarks

Compared to the original implementation the reworks performs up to 35% better. Also the pressure on the garbage collector is reduced. The Xbim.GLTF.IO.Benchmarks directory contains the benchmarks of the original implementation, the rework and the compatibility API.

Run it with

dotnet run -c Release

The result should look like this:

Method	Mean	Error	StdDev	Median
Convert	100.7 ms	5.81 ms	17.13 ms	97.26 ms
Convert_Compatibility	100.7 ms	4.74 ms	13.97 ms	97.76 ms
Convert_Deprecated	156.5 ms	6.01 ms	17.72 ms	151.38 ms

Authors

• @CBenghi - author of the original implementation

• @dn9090 - author of the rework