chore: expose app and gltf

[scarletsky]

Expose app and gltf for debugging models.

[donmccurdy]

Hi @scarletsky! I'm OK with this change, but would like to understand how this information is helpful for debugging. Do you mind saying a more about how it's used?

You may also find https://gltf.report/ helpful. Printing data in the script tab will show original information as found in the glTF file, rather than the three.js representation of that:

console.log( document.getRoot().listMaterials() );

[scarletsky]

@donmccurdy Hi. For me, exposing app is to get camera information. Sometimes I drop a glb file and the camera will clip the scene unexpectly as the nearClip or farClip may too small or too large. Sometimes I just want to check the json part of glb file, and there is no way go get it, because the original viewer just expose the gltf scene to window.content.

[donmccurdy]

Sounds good, thank you!