How to wait for bpy.ops.wm.alembic_import to finish?

Question

Quite a simple question I hope, I've been tearing my hair out with it for over a day now though. I'm trying to write a background python script that will import an alembic and then perform certain actions on it.

I can get the alembic to import by calling bpy.ops.wm.alembic_import with the filepath, however this import appears to occur in a separate thread which means that the code I immediately move on to still sees an empty scene.

Is there a way to make the python script execution wait until the import is finished, or insert a callback that will be called once the import is finished? I've tried the load_post and scene_update_post callbacks with no luck.

Answer 1

bpy.ops.wm.alembic_import operator provides a property called as_background_job which defaults to True. In that case the alembic import will happen asynchronously.

You can override the default behavior by passing a False value, in which case the import happens synchronously (blocking Blender)

bpy.ops.wm.alembic_import(filepath='....abc', as_background_job=False)

Answer 2

I had the same issue,

This is my current solution:

import bpy, time

#get size of total scene:
sceneSize = len(bpy.data.objects)

#do my import:
bpy.ops.wm.alembic_import(filepath="E:/Projects/blender/RenderCam.abc")

#wait for scene size to change:
elapsed = 0.0
maxTime = 10
while(sceneSize==len(bpy.data.objects) and elapsed < maxTime):
    time.sleep(0.2)
    elapsed += 0.2

#do something with imported thing:
bpy.context.scene.camera = bpy.data.objects["RenderCam"]

basically keep checking the size of the scene until it changes - then assume that the import is complete.

I welcome a better solution if anyone knows one.