Using new export GLTF edges functionality

Hello, could you please share the original file? Do it have edges? Some topology structure can have issues, we need to check and fix them if they exist.

As for an option - writing edge is enabled by default.

Best regards, Commenter-1,

Here's the original step file attached.

Is there a sample of a Step file that should work, that I can test?

You model have no "free edges", edges which are not a part of face topology. You can check the result on the model, where the free edges or vertexes presented.

Would an approach like this work?

// 1) Read STEP into an XDE document
    Handle(TDocStd_Document) doc = new TDocStd_Document("XmlOcaf");
    STEPCAFControl_Reader reader;
    reader.SetDocument(doc);
    if (reader.ReadFile(stepFile)    != IFSelect_RetDone ||
        !reader.Transfer(doc)) {
        std::cerr << "ERROR: cannot load STEP file\n";
        return 1;
    }

    // 2) Get top-level shapes
    Handle(XCAFDoc_ShapeTool) shapeTool =
        XCAFDoc_DocumentTool::ShapeTool(doc->Main());
    TDF_LabelSequence rootShapes;
    shapeTool->GetFreeShapes(rootShapes);

    // 3) Mesh each shape (so triangles exist) and extract _all_ edges
    TopoDS_Compound edgeCompound;
    BRep_Builder builder;
    builder.MakeCompound(edgeCompound);

    for (Standard_Integer i = 1; i <= rootShapes.Length(); ++i) {
        TDF_Label lbl = rootShapes.Value(i);
        TopoDS_Shape shape = shapeTool->GetShape(lbl);

        // ensure triangulation
        BRepMesh_IncrementalMesh mesh(shape, 1e-2);

        // iterate _every_ edge and add to compound
        for (TopExp_Explorer exp(shape, TopAbs_EDGE); exp.More(); exp.Next()) {
            TopoDS_Edge edge = TopoDS::Edge(exp.Current());
            builder.Add(edgeCompound, edge);
        }
    }

    // 4) Add that compound as a new “free” shape
    TDF_Label edgesLabel = shapeTool->NewShape();
    shapeTool->SetShape(edgesLabel, edgeCompound);
    rootShapes.Append(edgesLabel);

    // 5) Export original shapes + our edge compound
    RWGltf_CafWriter writer(gltfFile, false);
    writer.Perform(
      doc,
      rootShapes,      // labels to export
      nullptr,         // no label-filter
      TColStd_IndexedDataMapOfStringString(), 
      Message_ProgressRange()
    );

Yes, looks like that it will work. You can simply adding shape to doc, by just AddShape method.

Best regards, Commenter-1.

Thanks, and if you can explain one more thing. What would the correct way be, to check if the Step file already contains these free edges or not?

Check can be done by checking edge which are not a part of wire or wires not part of face:
Free edge - edge which is not a part of Face(through Wire).

  TopExp_Explorer anExpEdge(shape, TopAbs_EDGE, TopAbs_WIRE);
  TopExp_Explorer anExpWire(shape, TopAbs_WIRE, TopAbs_FACE);
  if (!anExpEdge.More() && !anExpWire.More())
  {
    // no free edges or wires
  }

Best regards, Commenter-1.

Ok, I was able to do this. At the beginning it wasn't working, it turns out it doesn't work with gltfWriter.SetMergeFaces(true). After turning it off the edges are added to the gltf. Seems like a bug to me, I can look into this a bit.

I also found that the exported edges look dashed. I opened an issue for this here, and I have a fix for that that I will submit now.

Yes, it looks like as a bug. Thank you.

Best regards, Commenter-1.

Hi Dmitrii,
Found a fix for the merged faces: https://github.com/Open-Cascade-SAS/OCCT/pull/554
Note that this reverts the fix with the linestrip I previously submitted. Details in the PR.

Is it possible to create these free edges from the original model, so that they are displayed in the gltf file?

Hey !
Did you find the solution ?