62 lines
2.6 KiB
Python
62 lines
2.6 KiB
Python
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"""Sum skin weights per bone group (finger vs hand vs rest) for each GLB. usage: weight_audit.py *.glb"""
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import json, struct, sys
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from pathlib import Path
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FING = ("thumb", "index", "middle", "ring", "pinky")
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def read_glb(path):
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data = Path(path).read_bytes()
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length = struct.unpack_from("<I", data, 8)[0]
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off = 12; gltf = None; binc = None
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while off < length:
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clen, ctype = struct.unpack_from("<II", data, off); off += 8
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if ctype == 0x4E4F534A: gltf = json.loads(data[off:off+clen])
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elif ctype == 0x004E4942: binc = data[off:off+clen]
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off += clen
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return gltf, binc
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def acc(gltf, binc, idx):
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a = gltf["accessors"][idx]
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bv = gltf["bufferViews"][a["bufferView"]]
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ncomp = {"SCALAR":1, "VEC2":2, "VEC3":3, "VEC4":4}[a["type"]]
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fmt = {5121:"B", 5123:"H", 5125:"I", 5126:"f"}[a["componentType"]]
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stride = bv.get("byteStride")
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size = struct.calcsize(fmt)*ncomp
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off = bv.get("byteOffset",0) + a.get("byteOffset",0)
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out = []
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for i in range(a["count"]):
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o = off + i*(stride or size)
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out.append(struct.unpack_from("<%d%s" % (ncomp, fmt), binc, o))
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return out, a["componentType"]
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for path in sys.argv[1:]:
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gltf, binc = read_glb(path)
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names = [nd.get("name", "") for nd in gltf["nodes"]]
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print(f"\n== {Path(path).name} ==")
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for mi, mesh in enumerate(gltf.get("meshes", [])):
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for pi, prim in enumerate(mesh.get("primitives", [])):
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att = prim["attributes"]
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if "JOINTS_0" not in att: continue
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# which skin uses this mesh
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skin_idx = next((nd.get("skin") for nd in gltf["nodes"]
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if nd.get("mesh") == mi and "skin" in nd), None)
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if skin_idx is None: continue
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joints = gltf["skins"][skin_idx]["joints"]
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jn = [names[j] for j in joints]
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J, _ = acc(gltf, binc, att["JOINTS_0"])
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W, wt = acc(gltf, binc, att["WEIGHTS_0"])
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wsc = 1.0 if wt == 5126 else (1/255 if wt == 5121 else 1/65535)
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fing_w = hand_w = 0.0
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fing_verts = 0
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for jrow, wrow in zip(J, W):
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fv = 0
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for j, w in zip(jrow, wrow):
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w *= wsc
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if w <= 0: continue
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n = jn[j].lower()
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if any(t in n for t in FING): fing_w += w; fv = 1
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elif n.startswith("hand"): hand_w += w
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fing_verts += fv
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print(f" mesh[{mi}] '{mesh.get('name','')}' prim{pi}: {len(J)} verts | "
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f"finger-weighted verts: {fing_verts} | total finger W: {fing_w:.0f} | hand W: {hand_w:.0f}")
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