Double-sided materials

[MadsHolten]

DoubleSided materials are not rendered correctly.

Below you see an example of the glTF taken directly from the zip loaded in an online viewer and here there is no problem.

The following fragments zip can be used for testing:
Duplex.zip

I tried making the following changes to fragment-ifc-importer/geometry.ts with no luck

private sortGeometriesByMaterials(
    geometryData: WEBIFC.PlacedGeometry,
    geometry: THREE.BufferGeometry
  ) {
    const materialID = this.saveMaterials(geometryData);
    if (!this._geometriesByMaterial[materialID]) {
      this._geometriesByMaterial[materialID] = [geometry];
    } else {
      this._geometriesByMaterial[materialID].push(geometry);
    }
    geometry.computeVertexNormals(); <----ADDED
  }

private saveNewMaterial(colorID: string, color: WEBIFC.Color) {
    console.log("SaveNewMat")
    this._materials[colorID] = new THREE.MeshLambertMaterial({
      color: new THREE.Color(color.x, color.y, color.z),
      transparent: color.w !== 1,
      opacity: color.w,
      side: THREE.DoubleSide <----ADDED
    });
}

[MadsHolten]

Probably the problem is with bim-fragment. I will try solving it here: https://github.com/IFCjs/fragment/blob/main/library/src/fragment-loader.ts

[MadsHolten]

I managed to fix it myself. In order to fully fix the problem one will have to 1) Implement this PR in fragments, 2) Publish a new version of fragments on npm, 3) Implement this PR and 4) Bump the version of fragments used here.

[agviegas]

Hey, sorry for the late reply, I missed this. I think that with the current implementation, you can set all the materials of a fragment set to be double sided by just traversing them and setting them as such. Don't you think this is better, as double sided materials have a higher computational cost? That way, the scene will be more efficient by default, and only people that need double sides will be able to set it up.

[agviegas]

Closing this for now, but open to discussing this further!