62 lines
2.2 KiB
Python
62 lines
2.2 KiB
Python
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"""Bake a hand-pose JSON into a body GLB by rewriting finger node rest rotations.
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IBMs untouched -> mesh deforms to the pose. usage: bake_preview.py body.glb pose.json out.glb"""
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import json, struct, sys
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from pathlib import Path
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body, posef, out = sys.argv[1:4]
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data = Path(body).read_bytes()
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length = struct.unpack_from("<I", data, 8)[0]
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off = 12
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chunks = []
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gltf = None
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while off < length:
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clen, ctype = struct.unpack_from("<II", data, off)
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off += 8
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if ctype == 0x4E4F534A:
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gltf = json.loads(data[off:off+clen].decode("utf-8"))
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chunks.append([ctype, None])
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else:
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chunks.append([ctype, data[off:off+clen]])
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off += clen
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pose = json.loads(Path(posef).read_text())["bones"]
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byname = {nd.get("name"): nd for nd in gltf["nodes"]}
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canon = None
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if len(sys.argv) > 4: # canonical-rest GLB: apply pose as rest-relative delta
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cdata = Path(sys.argv[4]).read_bytes()
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clen2 = struct.unpack_from("<I", cdata, 12)[0]
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cg = json.loads(cdata[20:20+clen2].decode("utf-8"))
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canon = {nd.get("name"): nd.get("rotation", [0, 0, 0, 1]) for nd in cg["nodes"]}
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def qmul(a, b):
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ax, ay, az, aw = a; bx, by, bz, bw = b
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return [aw*bx + ax*bw + ay*bz - az*by,
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aw*by - ax*bz + ay*bw + az*bx,
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aw*bz + ax*by - ay*bx + az*bw,
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aw*bw - ax*bx - ay*by - az*bz]
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n = 0
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for bone, quat in pose.items():
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if bone in byname:
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if canon is not None:
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cr = canon.get(bone, [0, 0, 0, 1])
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delta = qmul([-cr[0], -cr[1], -cr[2], cr[3]], quat) # canon_rest^-1 * pose
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body_rest = byname[bone].get("rotation", [0, 0, 0, 1])
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quat = qmul(body_rest, delta)
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byname[bone]["rotation"] = quat
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n += 1
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# strip animations so nothing overrides the pose
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gltf.pop("animations", None)
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js = json.dumps(gltf, separators=(",", ":")).encode("utf-8")
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js += b" " * ((4 - len(js) % 4) % 4)
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body_out = b""
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for ctype, payload in chunks:
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if ctype == 0x4E4F534A:
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payload = js
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body_out += struct.pack("<II", len(payload), ctype) + payload
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hdr = struct.pack("<III", 0x46546C67, 2, 12 + len(body_out))
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Path(out).write_bytes(hdr + body_out)
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print(f"baked {n}/{len(pose)} bones -> {out}")
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