obj2gltf_preserve.py

#!/usr/bin/env python3

"""
With an exiting OBJ and GLTF file, re-generate mesh from OBJ and overwrite
GLTF's, but preserve (some) GLTF properties.
"""

import argparse
from collections import OrderedDict
from os.path import splitext, isfile, dirname, basename
from subprocess import run
import json


GLTF_KEYS_PRESERVE = [
    "materials",
    "images",
    "textures",
    "scenes",
]


def convert(obj, gltf):
    run(
        ["obj2gltf", "-s", "-i", basename(obj), "-o", basename(gltf)],
        check=True, cwd=dirname(obj))
    # # Assimp corrupts the GLTF? :(
    # import pyassimp
    # scene = pyassimp.load(obj)
    # pyassimp.export(scene, gltf, file_type="gltf2")


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("obj", type=str)
    args = parser.parse_args()

    obj = args.obj
    assert isfile(obj), obj
    gltf = splitext(obj)[0] + ".gltf"
    assert isfile(gltf), glf

    # First, load original data.
    with open(gltf) as f:
        old = json.load(f, object_pairs_hook=OrderedDict)
    # Next, run conversion.
    convert(obj, gltf)
    # Now, update perserved keys.
    with open(gltf) as f:
        new = json.load(f, object_pairs_hook=OrderedDict)
    for key in GLTF_KEYS_PRESERVE:
        assert key in new, key
        new[key] = old[key]
    # Write changes.
    with open(gltf, "w") as f:
        json.dump(new, f, indent=2)
    print("Updated: {}".format(gltf))


assert __name__ == "__main__"
main()