writeJson after updating it result in loose data.

[CocoJr]

Update GLTF json make and merge it loose data.
I try to update the GLTF using the JSON.
I read one GLTF file, and merge it in a new document in an other folder.
The merge successfull, but the attribute I change in the JSON is simply lost.
The GLTF I load first to merge as Assets directory. I want to copy the Assets files in the new directory.

To Reproduce
Steps to reproduce the behavior:

        for (const modelPath of ['/app/3dmodels/adamHead/adamHead.gltf']) {
            const modelDir = path.dirname(modelPath);
            fs.ensureDirSync(modelDir+'/assets');
            // Read in json the model
            const jsonGltf = io.writeJSON(io.read(modelPath));
            for (const index in jsonGltf.json.images || []) {
                // copy the the image uri to the new directory
                if (jsonGltf.json.images) {
                    const newAssetFile = 'assets/'+path.basename(String(jsonGltf.json.images[index].uri));
                    await fs.copy(modelDir+'/'+jsonGltf.json.images[index].uri, newDir + '/' + newAssetFile);
                    jsonGltf.json.images[index].uri = newAssetFile;
                    console.log(jsonGltf.json.images[index], newAssetFile);
                }
            }
            // Merge into the new document
            document.merge(io.readJSON(jsonGltf));
            console.log('merged '+modelPath);
        }
        console.log('write');
        io.write(newDir+'/model.gltf', document);
        console.log('writed')

The image URI should took the new value, instead is just get removed.

The new JSON looks like:

  "images": [
    {
      "mimeType": "image/jpeg"
    },
    ....

instead of:

  "images": [
    {
      "mimeType": "image/jpeg",
      "uri": "assets/XXXX.jpg
    },
    ....

The file is still copied, so nothing wrong in my code. When i console.log the images attributes, i can see the URI. But it's not saved.

[donmccurdy]

Working with the raw JSON data is unforgiving, I wouldn't recommend that for anything more than cosmetic changes, or to load something in memory that the NodeIO and WebIO classes wouldn't otherwise be able to access. But if you do go that route, note that when changing a URI, you must also change the corresponding key in the jsonDocument.resources object. Those resources are held in memory, so io.readJSON(...) does not read anything from disk.

---

The preferred solution here would be to work with a Document instead of the raw JSON:

const document = io.read('input.gltf');

fs.ensureDirSync('path/to/assets');

for (const texture of document.getRoot().listTextures()) {
  texture.setURI('path/to/assets/' + path.basename(texture.getURI()));
}

io.write('output.gltf', document);