Convertion from STEP file to GLB

[qouv]

Hello!

I need a solution like literally in this link https://draw.sview.ru/xde-export-step2gltf/
It works perfect. And I want to implement it in a nodejs app. I am so new to OCC and have no knowledge on C++.

Do you guys think I am able to achieve same thing with opencascade.js?

Thanks everyone contributed to this project.

[donalffons]

Hey, implementing a simple step to gltf converter is easy. Less than 20-30 lines of code, I think.

Check out the starter template for nodejs (it's trivial). Then check out how the beginner example adds opencascade shapes to a document and then exports that as a glb file, which is used for rendering (via ObjectURL). Instead of creating an ObjectURL, you want to output the glb file to disk. For reading STEP files, there is STEPControl_Reader and STEPCAFControl_Reader - the latter is more powerful and can import colors and product structure.

[qouv]

Thank you Sebastian, you are the best!

I really could do with a structure like below, succesfully saved glb file. Now only problem is when I change STEPControl_Reader to STEPCAF_Control_Reader I get TypeError: reader.TransferRoots is not a function.

Since I need colored glb, I guess I should use STEPCAF one. I would appreciate if you could help.

const loadSTEPorIGES = async (openCascade, fileText, fileName) => {

    const fileType = (() => {
        switch (fileName.toLowerCase().split(".").pop()) {
            case "step":
            case "stp":
                return "step";
            case "iges":
            case "igs":
                return "iges";
            default:
                return undefined;
        }
    })();
    // Writes the uploaded file to Emscripten's Virtual Filesystem
    openCascade.FS.createDataFile("/", `file.${fileType}`, fileText, true, true);

    // Choose the correct OpenCascade file parsers to read the CAD file
    var reader = null;
    if (fileType === "step") {
        reader = new openCascade.STEPControl_Reader_1();
    } else if (fileType === "iges") {
        reader = new openCascade.IGESControl_Reader_1();
    } else { console.error("opencascade.js can't parse this extension! (yet)"); }
    const readResult = reader.ReadFile(`file.${fileType}`);            // Read the file
    if (readResult === openCascade.IFSelect_ReturnStatus.IFSelect_RetDone) {
        console.log("file loaded successfully!     Converting to OCC now...");
        const numRootsTransferred = reader.TransferRoots(new openCascade.Message_ProgressRange_1());    // Translate all transferable roots to OpenCascade
        const stepShape = reader.OneShape();         // Obtain the results of translation in one OCCT shape
        console.log(fileName + " converted successfully!  Triangulating now...");

        visualizeShapes(openCascade, stepShape);

        // Out with the old, in with the new!
        console.log(fileName + " triangulated and added to the scene!");

        // Remove the file when we're done (otherwise we run into errors on reupload)
        openCascade.FS.unlink(`/file.${fileType}`);
    } else {
        console.error("Something in OCCT went wrong trying to read " + fileName);
    }

};

function visualizeDoc(oc, doc) {
    // Export a GLB file (this will also perform the meshing)
    const cafWriter = new oc.RWGltf_CafWriter(new oc.TCollection_AsciiString_2("./file.glb"), true);
    cafWriter.Perform_2(new oc.Handle_TDocStd_Document_2(doc), new oc.TColStd_IndexedDataMapOfStringString_1(), new oc.Message_ProgressRange_1());
  
    // Read the GLB file from the virtual file system
    const glbFile = oc.FS.readFile("./file.glb", { encoding: "binary" });
    console.log(glbFile);
    fs.writeFileSync("./testfiles/file.glb", glbFile)
}


function visualizeShapes(oc, stepShape) {

    // Create a document add our shapes
    const doc = new oc.TDocStd_Document(new oc.TCollection_ExtendedString_1());
    const shapeTool = oc.XCAFDoc_DocumentTool.ShapeTool(doc.Main()).get();

    shapeTool.SetShape(shapeTool.NewShape(), stepShape);
    // Tell OpenCascade that we want our shape to get meshed
    new oc.BRepMesh_IncrementalMesh_2(stepShape, 0.1, false, 0.1, false);

    // Return our visualized document
    return visualizeDoc(oc, doc);
}

[donalffons]

STEPCAFControl_Reader does not have a function TransferRoots. Try something like this:

const reader = new oc.STEPCAFControl_Reader_1();
reader.ReadFile("./file.stp");
oc.FS.unlink('/file.stp');

if(!reader.Transfer_1(new oc.Handle_TDocStd_Document_2(doc), new oc.Message_ProgressRange_1())) throw new Error();
// now, the STEP file is in your document

[qouv]

Hello again,

For anybody needs something like what asked, I want to share my solution below.

@donalffons this is working. But too slow for big assemblies. Do you have any recommendations for increasing conversion speed?

import initOpenCascade from "opencascade.js/dist/node.js";
import fs from 'fs';
import path from 'path';

const loadSTEPorIGES = async (openCascade, file, fileName) => {

    const fileText = fs.readFileSync(file.path, 'utf8');

    const fileType = (() => {
        switch (fileName.toLowerCase().split(".").pop()) {
            case "step":
            case "stp":
                return "step";
            case "iges":
            case "igs":
                return "iges";
            default:
                return undefined;
        }
    })();
    // Writes the uploaded file to Emscripten's Virtual Filesystem
    openCascade.FS.createDataFile("/", `file.${fileType}`, fileText, true, true);

    // Choose the correct OpenCascade file parsers to read the CAD file
    var reader = null;
    if (fileType === "step") {
        reader = new openCascade.STEPCAFControl_Reader_1();
    } else if (fileType === "iges") {
        reader = new openCascade.IGESCAFControl_Reader_1();
    } else { console.error("opencascade.js can't parse this extension! (yet)"); }


    const readResult = reader.ReadFile(`file.${fileType}`);            // Read the file

    if (readResult === openCascade.IFSelect_ReturnStatus.IFSelect_RetDone) {
        console.log("file loaded successfully!     Converting to OCC now...");
        //const numRootsTransferred = reader.TransferRoots(new openCascade.Message_ProgressRange_1());    // Translate all transferable roots to OpenCascade

        // Create a document add our shapes
        const doc = new openCascade.TDocStd_Document(new openCascade.TCollection_ExtendedString_1());

        if (!reader.Transfer_1(new openCascade.Handle_TDocStd_Document_2(doc), new openCascade.Message_ProgressRange_1())) throw new Error();

        // Obtain the results of translation in one OCCT shape
        console.log(fileName + " converted successfully!  Triangulating now...");

        return visualizeShapes(openCascade, doc, fileName, fileType);

    } else {
        console.error("Something in OCCT went wrong trying to read " + fileName);
    }

};

function visualizeDoc(oc, doc, fileName, fileType) {

    const justName = path.parse(fileName).name;
    // Export a GLB file (this will also perform the meshing)
    const cafWriter = new oc.RWGltf_CafWriter(new oc.TCollection_AsciiString_2(`./${justName}.glb`), true);
    cafWriter.Perform_2(new oc.Handle_TDocStd_Document_2(doc), new oc.TColStd_IndexedDataMapOfStringString_1(), new oc.Message_ProgressRange_1());

    // Out with the old, in with the new!
    console.log(fileName + " triangulated and added to the scene!");

    // Remove the file when we're done (otherwise we run into errors on reupload)
    oc.FS.unlink(`/file.${fileType}`);
    // Read the GLB file from the virtual file system
    const glbFile = oc.FS.readFile(`./${justName}.glb`, { encoding: "binary" });
    const fileObj = { file: glbFile, filename: fileName };
    return fileObj;
}

function visualizeShapes(oc, doc, fileName, fileType) {
    
    const aRootLabels = new oc.TDF_LabelSequence_1();
    const aCompound = new oc.TopoDS_Compound();
    const shapeTool = oc.XCAFDoc_DocumentTool.ShapeTool(doc.Main()).get();

    shapeTool.GetFreeShapes(aRootLabels);

    const BRepBuilder = new oc.BRep_Builder();

    BRepBuilder.MakeCompound(aCompound);

    console.log(aRootLabels.Length());

    for (let i = 1; i <= aRootLabels.Length(); i++) {

        const aRootShape = new oc.TopoDS_Shape();
        const aRootLabel = aRootLabels.Value(i);

        if (oc.XCAFDoc_ShapeTool.GetShape_1(aRootLabel, aRootShape)) {
            BRepBuilder.Add(aCompound, aRootShape);
        }

    }

    const aDrawer = new oc.Prs3d_Drawer();
    const anAlgo = new oc.BRepMesh_IncrementalMesh_1();

    anAlgo.ChangeParameters().Deflection = 0.2;
    anAlgo.ChangeParameters().Angle = 20.0 * Math.PI / 180.0; // 20 degrees
    anAlgo.ChangeParameters().InParallel = true;
    anAlgo.SetShape(aCompound);
    anAlgo.Perform_1(new oc.Message_ProgressRange_1());

    console.log("hey");
    // Return our visualized document
    return  visualizeDoc(oc, doc, fileName, fileType);
}

const convertSTEPorIGES = async (file) => {
    const openCascade = await initOpenCascade();

    console.log("inside opencascade");
    return loadSTEPorIGES(openCascade, file, file.filename);
}

export default convertSTEPorIGES;

[donalffons]

Thanks for sharing the code! Hope that will be helpful for others.

Few remarks on improving performance:

• Using GLTFCAFWrite on the entire document will create unique meshes for every part, even if the same part is used multiple times. Depending on your use case, you could try to mesh + output the individual parts manually from OCCT. Then use the product structure and the transformation matrices to re-assemble everything into your scene graph in JS.
• Using multi-threading will greatly improve the performance during meshing. Check the docs and the SetParallel function of the meshing algorithm. Be aware that this means that you need to host your site with cross-origin-isolation headers.
• Some day soon this project will move towards using native WASM exceptions. This will also improve performance substantially. Meanwhile, you can disable exceptions. But be aware that this will break compatibility with some STEP files.

Currently, WASM supports only 32 bit memory addresses, which means you cannot use more than 4gigs of RAM. That limit can be reached quickly. Check OpenCascade's CADAssistant as a benchmark for performance and memory usage. In theory, it should be possible to get close to 150% of their performance...

[qouv]

I tried to change c++ code in the URL I shared to js, I couldn't nail only this line of code:

anAlgo.ChangeParameters().Deflection = Prs3d::GetDeflection (aCompound, aDrawer);

So I just gave a value of 0.2

[vdanielis]

Hello, I've tried running this code, but in the latest release (sept 2020), TDF_LabelSequence_1 is undefined (as well as Message_ProgressRange_1, but it runs without it). Until that line it runs.
Is there something I can do about it? Is there newer release available?