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182efca | 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 | """Export mesh data (vertices + triangles) to glTF binary (.glb) format."""
from __future__ import annotations
import numpy as np
import pygltflib
def _compute_normals(vertices: np.ndarray, triangles: np.ndarray) -> np.ndarray:
"""Compute smooth per-vertex normals by averaging face normals."""
normals = np.zeros_like(vertices, dtype=np.float32)
v0 = vertices[triangles[:, 0]]
v1 = vertices[triangles[:, 1]]
v2 = vertices[triangles[:, 2]]
face_normals = np.cross(v1 - v0, v2 - v0)
# Accumulate face normals to each vertex
for i in range(3):
np.add.at(normals, triangles[:, i], face_normals)
# Normalize
lengths = np.linalg.norm(normals, axis=1, keepdims=True)
lengths = np.maximum(lengths, 1e-10)
normals /= lengths
return normals.astype(np.float32)
def mesh_to_glb(vertices: np.ndarray, triangles: np.ndarray) -> bytes:
"""Convert vertices and triangles to a binary glTF (.glb) buffer.
Includes computed vertex normals for proper lighting/shading.
Args:
vertices: Mesh vertices with shape (N, 3), float64.
triangles: Triangle indices with shape (M, 3), int32.
Returns:
Bytes of the .glb file.
"""
vertices_f32 = vertices.astype(np.float32)
triangles_u32 = triangles.astype(np.uint32)
normals_f32 = _compute_normals(vertices_f32, triangles_u32)
# Byte buffers
vert_bytes = vertices_f32.tobytes()
norm_bytes = normals_f32.tobytes()
tri_bytes = triangles_u32.tobytes()
# Align each buffer to 4 bytes
def pad4(b: bytes) -> bytes:
pad = (4 - len(b) % 4) % 4
return b + b"\x00" * pad
vert_padded = pad4(vert_bytes)
norm_padded = pad4(norm_bytes)
blob = vert_padded + norm_padded + tri_bytes
total_bytes = len(blob)
norm_offset = len(vert_padded)
tri_offset = norm_offset + len(norm_padded)
v_min = vertices_f32.min(axis=0).tolist()
v_max = vertices_f32.max(axis=0).tolist()
gltf = pygltflib.GLTF2(
scene=0,
scenes=[pygltflib.Scene(nodes=[0])],
nodes=[pygltflib.Node(mesh=0)],
meshes=[
pygltflib.Mesh(
primitives=[
pygltflib.Primitive(
attributes=pygltflib.Attributes(POSITION=0, NORMAL=1),
indices=2,
)
]
)
],
accessors=[
# Accessor 0: vertex positions
pygltflib.Accessor(
bufferView=0,
componentType=pygltflib.FLOAT,
count=len(vertices_f32),
type=pygltflib.VEC3,
max=v_max,
min=v_min,
),
# Accessor 1: vertex normals
pygltflib.Accessor(
bufferView=1,
componentType=pygltflib.FLOAT,
count=len(normals_f32),
type=pygltflib.VEC3,
),
# Accessor 2: triangle indices
pygltflib.Accessor(
bufferView=2,
componentType=pygltflib.UNSIGNED_INT,
count=triangles_u32.size,
type=pygltflib.SCALAR,
max=[int(triangles_u32.max())],
min=[int(triangles_u32.min())],
),
],
bufferViews=[
# BufferView 0: positions
pygltflib.BufferView(
buffer=0,
byteOffset=0,
byteLength=len(vert_bytes),
target=pygltflib.ARRAY_BUFFER,
),
# BufferView 1: normals
pygltflib.BufferView(
buffer=0,
byteOffset=norm_offset,
byteLength=len(norm_bytes),
target=pygltflib.ARRAY_BUFFER,
),
# BufferView 2: indices
pygltflib.BufferView(
buffer=0,
byteOffset=tri_offset,
byteLength=len(tri_bytes),
target=pygltflib.ELEMENT_ARRAY_BUFFER,
),
],
buffers=[pygltflib.Buffer(byteLength=total_bytes)],
)
gltf.set_binary_blob(blob)
return b"".join(gltf.save_to_bytes())
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