42 lines
2 KiB
Python
42 lines
2 KiB
Python
# Packs a .gltf with external buffers and images into one self-contained .glb, which is the only
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# model format Singe loads. Usage: python3 util/packGlb.py Model.gltf Model.glb
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import json, os, struct, sys
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src, out = sys.argv[1], sys.argv[2]
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base = os.path.dirname(src)
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g = json.load(open(src))
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binary = bytearray()
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views = g.setdefault('bufferViews', [])
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def add(data):
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while len(binary) % 4: binary.append(0)
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off = len(binary); binary.extend(data)
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return off
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# Buffers: concatenate, remapping views.
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offsets = []
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for b in g.get('buffers', []):
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data = open(os.path.join(base, b['uri']), 'rb').read()
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offsets.append(add(data))
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for v in views:
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v['byteOffset'] = v.get('byteOffset', 0) + offsets[v.get('buffer', 0)]
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v['buffer'] = 0
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# Images: each becomes a buffer view with a mime type. The table is exhaustive on purpose: a
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# two-way png/jpeg guess quietly labelled every .ktx2 as image/jpeg, which Singe survives because it
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# sniffs the magic number, and which no other glTF reader has to.
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mimeTypes = {'png': 'image/png', 'jpg': 'image/jpeg', 'jpeg': 'image/jpeg', 'ktx2': 'image/ktx2', 'webp': 'image/webp', 'basis': 'image/basis'}
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for img in g.get('images', []):
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uri = img.pop('uri')
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data = open(os.path.join(base, uri), 'rb').read()
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ext = uri.lower().rsplit('.', 1)[-1]
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if ext not in mimeTypes:
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sys.exit('No mime type known for ' + uri + '; add it to mimeTypes in util/packGlb.py.')
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views.append({'buffer': 0, 'byteOffset': add(data), 'byteLength': len(data)})
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img['bufferView'] = len(views) - 1
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img['mimeType'] = mimeTypes[ext]
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while len(binary) % 4: binary.append(0)
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g['buffers'] = [{'byteLength': len(binary)}]
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js = json.dumps(g, separators=(',', ':')).encode()
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while len(js) % 4: js += b' '
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with open(out, 'wb') as f:
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f.write(struct.pack('<4sII', b'glTF', 2, 12 + 8 + len(js) + 8 + len(binary)))
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f.write(struct.pack('<II', len(js), 0x4E4F534A)); f.write(js)
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f.write(struct.pack('<II', len(binary), 0x004E4942)); f.write(binary)
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print(out, os.path.getsize(out), 'bytes')
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