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9f85448 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 | """Minimal glTF binary reader."""
from __future__ import annotations
import json
import struct
from dataclasses import dataclass, field
from pathlib import Path
import cv2
import numpy as np
_JSON_CHUNK = 0x4E4F534A
_BIN_CHUNK = 0x004E4942
_DTYPES = {
5120: np.int8, 5121: np.uint8, 5122: np.int16,
5123: np.uint16, 5125: np.uint32, 5126: np.float32,
}
_COUNTS = {"SCALAR": 1, "VEC2": 2, "VEC3": 3, "VEC4": 4, "MAT2": 4, "MAT3": 9, "MAT4": 16}
@dataclass
class Primitive:
"""One drawable mesh piece."""
positions: np.ndarray
normals: np.ndarray
joints: np.ndarray
weights: np.ndarray
triangles: np.ndarray
color: tuple[int, int, int] = (185, 180, 175)
uv: np.ndarray | None = None
texture: np.ndarray | None = None
@dataclass
class Node:
"""One scene node."""
name: str
matrix: np.ndarray
children: list[int] = field(default_factory=list)
parent: int | None = None
@dataclass
class Gltf:
"""Loaded model."""
nodes: list[Node]
primitives: list[Primitive]
joints: list[int]
inverse_bind: np.ndarray
globals: np.ndarray
def _node_matrix(node: dict) -> np.ndarray:
"""Local transform of one node."""
if "matrix" in node:
return np.array(node["matrix"], dtype=np.float64).reshape(4, 4).T
m = np.eye(4)
if "rotation" in node:
x, y, z, w = node["rotation"]
m[:3, :3] = np.array([
[1 - 2 * (y * y + z * z), 2 * (x * y - z * w), 2 * (x * z + y * w)],
[2 * (x * y + z * w), 1 - 2 * (x * x + z * z), 2 * (y * z - x * w)],
[2 * (x * z - y * w), 2 * (y * z + x * w), 1 - 2 * (x * x + y * y)],
])
if "scale" in node:
m[:3, :3] = m[:3, :3] @ np.diag(node["scale"])
if "translation" in node:
m[:3, 3] = node["translation"]
return m
def _decode_image(js: dict, blob: bytes, image_index: int) -> np.ndarray | None:
"""Decode one embedded glTF image to a BGR array."""
images = js.get("images") or []
if not 0 <= image_index < len(images):
return None
image = images[image_index]
if "bufferView" not in image:
return None
view = js["bufferViews"][image["bufferView"]]
start = view.get("byteOffset", 0)
raw = np.frombuffer(blob, dtype=np.uint8, count=view["byteLength"], offset=start)
decoded = cv2.imdecode(raw, cv2.IMREAD_COLOR)
return decoded if decoded is not None and decoded.size else None
def _material_texture(js: dict, blob: bytes, material_index: int) -> np.ndarray | None:
"""Base-color texture of one material, if it has an embedded one."""
pbr = js["materials"][material_index].get("pbrMetallicRoughness", {})
ref = pbr.get("baseColorTexture")
if ref is None:
return None
textures = js.get("textures") or []
if not 0 <= ref.get("index", -1) < len(textures):
return None
source = textures[ref["index"]].get("source")
return None if source is None else _decode_image(js, blob, source)
class _Reader:
"""Accessor decoder."""
def __init__(self, js: dict, blob: bytes) -> None:
self.js = js
self.blob = blob
def __call__(self, index: int) -> np.ndarray:
"""Read one accessor."""
acc = self.js["accessors"][index]
dtype = _DTYPES[acc["componentType"]]
ncomp = _COUNTS[acc["type"]]
count = acc["count"]
if "bufferView" not in acc:
return np.zeros((count, ncomp), dtype=np.float64)
view = self.js["bufferViews"][acc["bufferView"]]
start = view.get("byteOffset", 0) + acc.get("byteOffset", 0)
stride = view.get("byteStride") or np.dtype(dtype).itemsize * ncomp
item = np.dtype(dtype).itemsize * ncomp
if stride == item:
raw = np.frombuffer(self.blob, dtype=dtype, count=count * ncomp, offset=start)
out = raw.reshape(count, ncomp)
else:
rows = [np.frombuffer(self.blob, dtype=dtype, count=ncomp, offset=start + i * stride)
for i in range(count)]
out = np.stack(rows)
return out.astype(np.float64) if dtype == np.float32 else out
def load(path: str | Path) -> Gltf:
"""Read a glb file."""
path = Path(path)
if not path.exists():
raise FileNotFoundError(f"Character model not found: {path}")
data = path.read_bytes()
magic, _version, total = struct.unpack_from("<III", data, 0)
if magic != 0x46546C67:
raise ValueError(f"Not a binary glTF: {path}")
js: dict | None = None
blob = b""
off = 12
while off < total:
length, kind = struct.unpack_from("<II", data, off)
chunk = data[off + 8:off + 8 + length]
if kind == _JSON_CHUNK:
js = json.loads(chunk)
elif kind == _BIN_CHUNK:
blob = bytes(chunk)
off += 8 + length + ((4 - length % 4) % 4 if length % 4 else 0)
if js is None:
raise ValueError(f"No json chunk in {path}")
read = _Reader(js, blob)
nodes = [Node(name=n.get("name", f"node{i}"), matrix=_node_matrix(n),
children=list(n.get("children", []))) for i, n in enumerate(js["nodes"])]
for i, node in enumerate(nodes):
for c in node.children:
nodes[c].parent = i
globals_ = np.tile(np.eye(4), (len(nodes), 1, 1))
order = [i for i in range(len(nodes)) if nodes[i].parent is None]
while order:
i = order.pop(0)
parent = nodes[i].parent
base = globals_[parent] if parent is not None else np.eye(4)
globals_[i] = base @ nodes[i].matrix
order.extend(nodes[i].children)
skin = js["skins"][0]
joints = list(skin["joints"])
inverse_bind = read(skin["inverseBindMatrices"]).reshape(-1, 4, 4).transpose(0, 2, 1)
primitives: list[Primitive] = []
for mesh in js.get("meshes", []):
for prim in mesh["primitives"]:
attrs = prim["attributes"]
if "JOINTS_0" not in attrs or "WEIGHTS_0" not in attrs:
continue
pos = read(attrs["POSITION"])
normals = read(attrs["NORMAL"]) if "NORMAL" in attrs else np.zeros_like(pos)
jnt = read(attrs["JOINTS_0"]).astype(np.int32)
wts = read(attrs["WEIGHTS_0"]).astype(np.float64)
wsum = wts.sum(axis=1, keepdims=True)
wts = wts / np.where(wsum > 1e-9, wsum, 1.0)
if "indices" in prim:
idx = read(prim["indices"]).astype(np.int64).reshape(-1)
else:
idx = np.arange(len(pos), dtype=np.int64)
color = (185, 180, 175)
texture = None
mat = prim.get("material")
if mat is not None:
pbr = js["materials"][mat].get("pbrMetallicRoughness", {})
base = pbr.get("baseColorFactor")
if base:
color = tuple(int(np.clip(c * 255, 0, 255)) for c in base[2::-1])
texture = _material_texture(js, blob, mat)
uv = read(attrs["TEXCOORD_0"]) if "TEXCOORD_0" in attrs else None
if texture is None:
uv = None
primitives.append(Primitive(positions=pos, normals=normals, joints=jnt,
weights=wts, triangles=idx.reshape(-1, 3),
color=color, uv=uv, texture=texture))
return Gltf(nodes=nodes, primitives=primitives, joints=joints,
inverse_bind=inverse_bind, globals=globals_)
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