exports merged gltf file for objects in each collection, while retaining structure of collections as directories. Also properly selects armature's parented objects automatically.

export_collections_with_structure.py

"""
Blender batch export script with subdir / auto centering / output redirection.

Exports all objects in respective collections that doesn't start with IGNORE_PREFIX.

Files will be saved in script's named subdir, which means script must be saved first.

No need to center every object into world center - script will handle that.

Written by jupiterbjy@gmail.com
"""

import os
import pathlib
import json

import bpy

# CONFIG --------------

EXPORT_TYPE = "gltf"
SCALE = 1.0

IGNORE_PREFIX = "_"

# ---------------------


# select extension and exporter
EXTENSION = {
    "gltf": ".glb",
    "fbx": ".fbx",
    "stl": ".stl",
}[EXPORT_TYPE]

EXPORTER = {
    "gltf": getattr(bpy.ops.export_scene, "gltf"),
    "fbx": getattr(bpy.ops.export_mesh, "fbx"),
    "stl": getattr(bpy.ops.export_mesh, "stl"),
}[EXPORT_TYPE]

# check if file is saved
if not bpy.data.filepath:
    raise Exception("Blend file is not saved")

# init basedir
_file = pathlib.Path(bpy.data.filepath)


basedir = _file.parent / _file.stem
basedir.mkdir(exist_ok=True)



# cache view layer
view_layer = bpy.context.view_layer



# shadow print() for output redirection to UI ---------

_overrides = []

for window in bpy.context.window_manager.windows:
    _overrides.extend(
        {"window": window, "screen": window.screen, "area": area} for area in window.screen.areas if
        area.type == "CONSOLE"
    )


def print(*args, sep=""):
    for override in _overrides:
        with bpy.context.temp_override(**override):
            bpy.ops.console.scrollback_append(text=sep.join(map(str, args)), type="OUTPUT")



def _visit(collection, root):
    if collection.name[0] == "_":
        print(f"Skipping {root}/{collection.name}")
        return
    
    objs = []
    
    for obj in collection.objects:
        if obj.name[0] == "_":
            print(f"Skipping {root}/{collection.name}/{obj.name}")
            continue
        objs.append(obj)    
    
    if objs:
        yield (objs, "/".join((root, collection.name)))
    
    print(collection.name)
    for child_collection in collection.children:
        yield from _visit(child_collection, "/".join((root, collection.name)))


def visit():
    """Visit collection recursively and yield (object, str_collection_path) pairs"""
    
    for collection in bpy.context.scene.collection.children:
        yield from _visit(collection, "")


def save_obj(objs, col_path):
    """Save given object at collection path"""
    
    bpy.ops.object.select_all(action='DESELECT')
    
    # prep path
    base_path = basedir / col_path
    base_path.mkdir(exist_ok=True, parents=True)
    
    # prep name from collection
    name = "_".join(part.lower() for part in base_path.stem.split())
    
    # build clean path without illegal characters
    fn = base_path / (bpy.path.clean_name(name) + EXTENSION)

    # cache old pos, assuming all objects has same origin
    old_pos = objs[0].location[:]
    old_scale = objs[0].scale[:]

    # some exporters only use the active object - make sure it's selected and active
    objs[0].select_set(True)
    view_layer.objects.active = objs[0]
    
    # select all obj in list
    for obj in objs:
        obj.select_set(True)
        
        # if armature, select all meshes parented to the armature
        if obj.type == "ARMATURE":
            for child_obj in obj.children:
                child_obj.select_set(True)
        
        # move object to world center - or some exporter like gltf keeps offset when saving
        # need to cache old position explicitly
        obj.location = (0, 0, 0)
        obj.scale = (SCALE, SCALE, SCALE)

    # export
    EXPORTER(filepath=fn.as_posix(), export_apply=True, use_selection=True)
    print("written: ", fn)

    # reset scale and position
    for obj in objs:
        obj.location = old_pos
        obj.scale = old_scale
    
    bpy.ops.object.select_all(action='DESELECT')


# Driver ---

def main():
    # only works in object mode, so change to that
    bpy.ops.object.mode_set(mode="OBJECT")
    
    # for each cached selection export
    for obj, col_path in visit():
        
        # strip preceeding slash
        save_obj(obj, col_path[1:])


main()
bpy.ops.object.select_all(action='DESELECT')