Figura v5 support

This Figura addon adds compatibility with Blockbench 5.0's updated model format. (and a few other nice things, too!)

These changes will mostly likely be included as part of the next major Figura update, as part of PR #448. That might take a while to release; this addon serves as an interim solution.

The code in this addon is the same as in the aformentioned pull request, along with a mixin to integrate the new code.

Features!

• Support for 5.0 model files (the main reason you're here)
• Better error messages for animation keyframes (these are tied pretty closely into the importing process)
• A fix for require that caused it to not work on Windows if the "name" of the code calling it has characters that would be illegal if used in the filesystem (notably, ? is used in the improved animation keyframe changes)

About 1.16.5

I don't really want to do the refactoring work to make the code work with Java 8 for this addon; it'll happen for Figura eventually, but unfortuately that means you can't use this addon on 1.16.5 (which uses Java 8.)

Do I need this?

for all users

• You need to keep this addon installed to continue to load models from the filesystem created with Blockbench 5.0.0 or later.
• You do not need this addon to load avatars uploaded by other people with this addon.
• You do not need this addon to load avatars that have been uploaded to the cloud by you using this addon in another instance (it only impacts compiling local avatars)
• You might need this addon to use an avatar you downloaded from the internet. This is usually indicated if loading fails with a message like Cannot invoke "..." because the return value of "..." is null, but there are other reasons that error could appear as well.

Do other people need this?

• See point 2 above, and the section below.
• No if you're just uploading your avatar to the Figura cloud.
• Yes if you're sharing the avatar with other people as e.g. a .zip file.

Mind the gap

for avatar creators

• If you're sharing avatars you created, please either stick to 4.12 for now, or make it very obvious that this addon is required. This will hopefully prevent confusion from your users if they try to load your avatar and it doesn't work.

Modpacks?

Of course! (also it's MIT licensed, you don't need my permission for this)