[Feature] Add basic support for MSFT_lod extension

[ptc-tgamper]

Hi,

This changeset adds support to parse and serialize node and material LODs via MSFT_lod extension. The extension's specification can be found at https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Vendor/MSFT_lod

There are already viewers and toolkits that support it, such as Microsoft's https://github.com/microsoft/glTF-Toolkit, Babylon.JS and three.js. There is also a Blender plugin for export, probably others.

Moreover, this also fixes a crasher in KHR_audio related code.

[syoyo]

Awesome! Let me give some time to review PR.

Moreover, this also fixes a crasher in KHR_audio related code.

Do you have minimal reproducible gltf/code for this?

[ptc-tgamper]

I'll try to come up with a test case for the KHR_audio serialization crash. AFAICT one needs to have asserts enabled for it to happen.

[ptc-tgamper]

Added a testcase for the KHR_audio node serialization crasher.

[syoyo]

@ptc-tgamper

Added a testcase for the KHR_audio node serialization crasher.

Thanks!

Is it ok to merge? Do you have further commit planned?

[ptc-tgamper]

I think I will come up with follow-up PRs. For now, this gives me the basic functionality I need. Please merge 👍

[syoyo]

Thanks! Merged!