BIM tiles backend handle

as working with ifc.js Components using Fragment IFC Streaming I had an issue handling files in backend I need to know which files I need to put in backend to have it streaming ?

`let filestream = fs.createReadStream(__dirname + '/small.ifc-processed.json');

app.get('/small.ifc-processed-global', (req, res) => {

filestream.pipe(res); })

after checking the source code, I could see that the FragmentIfcStreamer loader is asking to fetch a fragment file from a url (your backend).

const groupUrl = this.url + globalDataFileId;
    const groupData = await fetch(groupUrl);

https://github.com/ThatOpen/engine_components/blob/main/src/fragments/FragmentIfcStreamer/src/fragment-stream-loader.ts#L144-L149

Thus you can set a url that points to your .frag file to load the geometries. Check this sample how do I managed to load geometries directly from the front-end:

const loader = new OBC.FragmentStreamLoader(
  components
);
loader.url = "/fragments/"; //path inside my public folder in my frontend

const rawGeometryData = await fetch(
  "/tiles/mymodelBIMtiles.ifc-global.json"
);//path inside my public folder in my frontend

const geometryData =
  await rawGeometryData.json();
await loader.load(
  geometryData,
  true,
  undefined
);

and your json bim tiles should have the name of your fragment under the globalDataFileId property:

  ...
  "globalDataFileId": "mymodel.frag"
}

This way the IFCstreamer will fetch from the given url and the fragment file name, like this:

await fetch("/fragments/mymodel.frag")

this is my public folder structure by the way

Hope this was helpful and it serve as reference when reading the properties.