Multi thread import

[aronwk-aaron]

This should make importing faster, especially on large models, as it should take only as long as the longest import of a single LOD to execute

[aronwk-aaron]

@cdmpants could you tests these changes some when you have the time

[30350n]

Just going to mention that bpy/Blender is not thread safe at all. If you're trying to "multi thread" any code that interacts with bpy, Blender will inevitably crash.

[aronwk-aaron]

Just going to mention that bpy/Blender is not thread safe at all. If you're trying to "multi thread" any code that interacts with bpy, Blender will inevitably crash.

Definitely! I did a fair bit of research on that, and from what I found, I/O is one of the very few things that doesn't care as much as other stuff and ThreadPoolExecutor was the safest ways to handle it. And I had to move where it links the collection to the parent or because the parent did not like being worked on from multiple threads.

I tested this by importing few models and some crashed, but they also crashed before these changes(last time I tested importing most of these models was before we moved to 3.1). So I'm guessing my laptop is scuffed since I run Arch Linux btw, or 3.1 introduce since issues with importing. I'll need someone else to verify this though, so I'm just waiting lol