Support exporting embedded .gltf

Is your feature request related to a problem? Please describe.

Currently (using WebIO in my case), you can use the writeBinary function to export as .glb, and the writeJSON function to export as .gltf with external resources.

It would be useful to have also the “.gltf embedded” option like blender does:

In my usecase, I need the json to be stored in another json file.

Describe the solution you’d like A function like writeJSONEmbedded or something that returns just the json object with the resources embedded in base64 in the object.

Describe alternatives you’ve considered Doing it myself (geometry only in this case):

const encodedBuffer = base64js.fromByteArray(new Uint8Array(resources['.bin']));
gltfCompressed.buffers[0].uri = `data:application/octet-stream;base64,${encodedBuffer}`;

[lexaknyazev]

This adds a 25-30% size penalty

Nit: base64 encodes each 3 bytes as 4, so it adds 33% size penalty.

[donmccurdy]

There are no Data URIs in a .glb file¹ – it’s binary data with the JSON prepended, similar to a file header. A .gltf file cannot contain binary data and so encoding binary as Data URIs (base64 strings) is necessary instead. This adds a 25-30% size penalty compared to binary data in a .glb, and decoding the Data URI can sometimes block the main thread in web browsers. If the final assets were gzipped, the size penalty might be lower but additional parsing cost is the same.

<small>¹ Technically you could combine them, but there’s no reason to and I’ve never seen it done.</small>