GLTFExporter and Scene Viewer don't get along

[yoavniran]

Hi there,
I'm guessing this is a long shot, but perhaps someone has some experience with the following:

I'm working on a 3D Viewer / AR Viewer that also allows users to apply color/textures changes on the viewed model.
Then I want to make it possible to see the model in AR on a mobile device including the user made changes.

I was inspired by the iOS Quick Look code to use the GLTFExporter in order to export the modified scene on the fly and hand it over to the SceneViewer as an Object URL. However, the scene viewer always opens and then closes (crashes) without being able to load the model.

With several models I tried, even if I just run the model through the export, without any changes, it just seems to break.

In the case of the Astronaut, not making changes and running through the exporter did load fine in SV. However, if I change the color of a material and try to export and load into the Viewer, it breaks. The model-viewer editor is able to show it just fine though:

Is there a known issue with the Exporter? Or is there a way to debug why the SV is crashing?

I tried playing with the exporter options (trs, onlyVisible, includeCustomExtensions) but that didn't seem to have any effect.

This is my (simplified) code:

const exportGltf = (options) => {
					const exporter = new GLTFExporter();
					return new Promise((resolve, reject) => {
						exporter.parse(gltf.scene, resolve, reject, options);
					});
				},


const loadAr = async () => {
	const anchor = document.createElement("a");

	const buffer = await exportGltf();
	const blob = new Blob([buffer], {
		type: "model/gltf-binary",
	});

	const objectUrl = URL.createObjectURL(blob);
	const exportedUrl = new URL(objectUrl, self.location.toString());

       anchor.setAttribute("href",
                    getSceneViewerIntentUrl({
			    src: exportedUrl,
			    fallbackUrl,
			}));

      anchor.click();
};

Thanks!

[elalish]

I think you have a misunderstanding - Scene Viewer is Android-only; you mention iOS, which would be Quick Look. Also, Quick Look can represent an updated model because USDZExporter exports on the fly from the scene. Scene Viewer cannot do this because it redownloads the URL from the server, so blobs don't work. However, WebXR works fine on Android since it's still the same scene in the browser. Does that help?

[elalish]

No, we don't use GLTFExporter. QL uses USDZExporter, hence why QL works. SV really isn't capable of using an object URL - we just forward the original src URL to it, hence why it always shows the unmodified version. If SV is crashing, that's a SV issue, and I'd be happy to forward it if you can give us an easy way to reproduce.

[yoavniran]

That'd be great!
Here's a test page opening my Viewer. On an Android device it should show the astronaut with a "open in AR" button.

Clicking the button should open the Scene Viewer and it crashes every time for me.
If you could pass that along to the SV folks, it would be awesome.

Thanks!

[elalish]

As I say, you can't pass an ObjectURL to Scene Viewer - it means nothing outside of the browser. It shouldn't crash, but it also has no way to work.

[yoavniran]

The following URL takes the model, exports it with GLTFExporter, and provides the object URL, which does load in the Scene Viewer successfully:

Its the same model (astronaut) and same code. Only difference is that there was no change to texture/material...

[elalish]

Interesting - news to me that it works that way. @AdrianAtGoogle Can Scene Viewer really handle ObjectURLs now? I don't know what this guy did - it's not MV and his code is obfuscated.