Unity 6.6: changes we used to get UnityGLTF working in a consumer project

[CharlieHess]

Unity 6.6 viability notes

This branch is not presented as a finished Unity 6.6 support release. It is a record of the changes we used in a consumer project to get UnityGLTF working again on Unity 6.6 alpha.

What this fixes

• Replaces exporter-side GetInstanceID() usage that turns into hard failures on Unity 6.6 with GetEntityId()-based keys and labels.
• Updates editor asset creation code to the newer AssetCreationEndAction and EntityId APIs.
• Updates editor state and preview tracking code to use entity ids where Unity 6.6 no longer accepts instance ids.
• Forces the rough refraction renderer feature onto the RenderGraph-compatible path on newer Unity 6 releases where the older compatibility path is no longer viable.
• Replaces one Visual Scripting exporter GUID.Generate() call with Guid.NewGuid() to avoid an editor-side API mismatch we hit during the migration.

Scope and limits

• This branch is intentionally narrow. It captures the concrete changes we needed for Unity 6.6 viability, not a broad compatibility audit across all UnityGLTF features.
• The validation evidence comes from the consumer project integration described above. We did not run a separate full UnityGLTF package test pass in this forked workspace.
• We left out unrelated package metadata and Unity-authored serialization noise from the consumer branch so the patch stays focused on the actual compatibility edits.

[CLAassistant]

All committers have signed the CLA.

[hybridherbst]

Thanks for posting this! We've not yet looked into Unity 6.6 (focus is on stability in LTS releases), but it's good to get a heads-up about changes needed there.