from __future__ import annotations
from typing import Any, NamedTuple, cast
import numpy as np
import numpy.typing as npt
import pygltflib
[docs]
class GltfAttribute(NamedTuple):
"""
A high level representation of a gltf attribute
`accessor_type` can only take `values autorized by the spec <https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#_accessor_type>`_.
`component_type` should take `these values <https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#_accessor_componenttype>`_.
"""
name: str
accessor_type: str # Literal["SCALAR", "VEC2", "VEC3"] # pygltflib.SCALAR | pygltflib.VEC2 | pygltflib.VEC3
component_type: pygltflib.UNSIGNED_BYTE | pygltflib.UNSIGNED_INT | pygltflib.FLOAT
array: npt.NDArray[np.uint8 | np.uint16 | np.uint32 | np.float32]
[docs]
def get_component_type_from_dtype(dt: np.dtype[Any]) -> int:
val = None
if dt == np.int8:
val = pygltflib.BYTE
elif dt == np.uint8:
val = pygltflib.UNSIGNED_BYTE
elif dt == np.int16:
val = pygltflib.SHORT
elif dt == np.uint16:
val = pygltflib.UNSIGNED_SHORT
elif dt == np.uint32:
val = pygltflib.UNSIGNED_INT
elif dt == np.float32:
val = pygltflib.FLOAT
else:
raise ValueError(f"Cannot find a component type suitable for {dt}")
return cast(int, val)
[docs]
class GltfPrimitive:
"""
A data structure storing all information to create a glTF mesh's primitive.
This is intended for higher-level usage than pygltflib.Primitive.
The transformation will be done automatically while transforming a `GltfMesh`.
:param triangles: array of triangle indices, must have a (n, 3) shape.
:param material: a glTF material. If not set, a default material is created.
:param texture_uri: the URI of the texture image if the primitive is textured.
"""
def __init__(
self,
triangles: npt.NDArray[np.uint8 | np.uint16 | np.uint32] | None = None,
material: pygltflib.Material | None = None,
texture_uri: str | None = None,
) -> None:
self.triangles: GltfAttribute | None = (
GltfAttribute(
"INDICE",
pygltflib.SCALAR,
get_component_type_from_dtype(triangles.dtype),
triangles,
)
if triangles is not None
else None
)
self.material: pygltflib.Material | None = material
self.texture_uri: str | None = texture_uri
[docs]
class GltfMesh:
"""
A data structure representing a mesh.
This is intended for higher-level usage than pygltflib.Mesh, which are an exact translation of the specification.
This is intented to be easier to construct by keeping a more hierarchical and logical organization. `GltfMesh` are constructed with all the vertices, normals, uvs and additional attributes, and an optional list of `GltfPrimitive` that contains indices and material informations.
Use `gltf_from_meshes` or `populate_gltf_from_mesh` to convert it to GLTF format.
:param points: array of vertex positions, must have a (n, 3) shape.
:param primitives: array of GltfPrimitive
:param normals: array of vertex normals for the whole mesh, must have a (n, 3) shape.
:param batchids: array of batch table IDs, must have a (n) shape.
:param additional_attributes: additional attributes to add to the primitive.
:param uvs: array of texture coordinates, must have a (n, 2) shape.
"""
def __init__(
self,
points: npt.NDArray[np.float32],
name: str | None = None,
normals: npt.NDArray[np.float32] | None = None,
primitives: list[GltfPrimitive] | None = None,
batchids: npt.NDArray[np.uint32] | None = None,
uvs: npt.NDArray[np.float32] | None = None,
additional_attributes: list[GltfAttribute] | None = None,
properties: dict[str, Any] | None = None,
) -> None:
"""
A data structure storing all information to create a glTF mesh's primitive.
"""
if points is None or len(points.shape) < 2 or points.shape[1] != 3:
raise ValueError(
"points arguments should be an array of coordinate triplets (of shape (N, 3))"
)
self.points: GltfAttribute = GltfAttribute(
"POSITION", pygltflib.VEC3, pygltflib.FLOAT, points
)
self.name = name
self.primitives = primitives or []
if not self.primitives:
self.primitives.append(GltfPrimitive())
self.normals: GltfAttribute | None = (
GltfAttribute("NORMAL", pygltflib.VEC3, pygltflib.FLOAT, normals)
if normals is not None
else None
)
self.batchids: GltfAttribute | None = (
GltfAttribute(
"_BATCHID", pygltflib.SCALAR, pygltflib.UNSIGNED_INT, batchids
)
if batchids is not None
else None
)
self.uvs: GltfAttribute | None = (
GltfAttribute("TEXCOORD_0", pygltflib.VEC2, pygltflib.FLOAT, uvs)
if uvs is not None
else None
)
self.additional_attributes: list[GltfAttribute] = (
additional_attributes if additional_attributes is not None else []
)
self.properties = properties
[docs]
def gltf_from_meshes(
meshes: list[GltfMesh], transform: npt.NDArray[np.float32] | None = None
) -> pygltflib.GLTF2:
"""
Builds a GLTF2 instance from a list of meshes.
"""
gltf = pygltflib.GLTF2(
scene=0,
scenes=[pygltflib.Scene(nodes=[])],
nodes=[],
meshes=[],
)
# insert the default material
# if we don't add it there, we would have to test if one primitive doesn't have one and add
# only in this case, but we'd need to remember the material_id of the default material.
# For a few bytes, it's not worthy to do all this.
# it also makes debugging easier. material_id = 0 is the default material, and that's it.
# Note that the specification is ambiguous here, it's not clear if a gltf should always have a
# default material OR if it's the viewer's job.
gltf.materials.append(pygltflib.Material())
for i, mesh in enumerate(meshes):
node = pygltflib.Node(
mesh=i,
matrix=(transform.flatten("F").tolist() if transform is not None else None),
)
gltf.scenes[0].nodes.append(i)
gltf.nodes.append(node)
populate_gltf_from_mesh(
gltf,
mesh,
)
gltf.buffers = [pygltflib.Buffer(byteLength=len(gltf.binary_blob()))]
if len(gltf.textures) > 0:
gltf.samplers.append(
pygltflib.Sampler(
magFilter=pygltflib.LINEAR,
minFilter=pygltflib.LINEAR_MIPMAP_LINEAR,
wrapS=pygltflib.REPEAT,
wrapT=pygltflib.REPEAT,
)
)
return gltf
def _set_texture_to_primitive(
gltf: pygltflib.GLTF2, material: pygltflib.Material, texture_uri: str
) -> None:
gltf.images.append(pygltflib.Image(uri=texture_uri))
gltf.textures.append(pygltflib.Texture(sampler=0, source=len(gltf.images) - 1))
if material.pbrMetallicRoughness is None:
material.pbrMetallicRoughness = pygltflib.PbrMetallicRoughness()
if material.pbrMetallicRoughness.baseColorTexture is None:
material.pbrMetallicRoughness.baseColorTexture = pygltflib.TextureInfo()
material.pbrMetallicRoughness.baseColorTexture.index = len(gltf.textures) - 1
def _create_gltf_primitive(
gltf: pygltflib.GLTF2, primitive: GltfPrimitive
) -> pygltflib.Primitive:
material_id = None
if primitive.material:
gltf.materials.append(primitive.material)
material_id = len(gltf.materials) - 1
else:
# default material
# it will always be 0 by internal py3dtiles convention
material_id = 0
return pygltflib.Primitive(
attributes=pygltflib.Attributes(),
material=material_id,
)
[docs]
def populate_gltf_from_mesh(
gltf: pygltflib.GLTF2,
mesh: GltfMesh,
) -> None:
"""
Add a GltfMesh to a pygltflib.GLTF2
This method takes care of all the nitty-gritty work about setting buffer, bufferViews, accessors and primitives.
"""
# see https://gitlab.com/dodgyville/pygltflib/#create-a-mesh
gltf_binary_blob = cast(bytes, gltf.binary_blob()) or b""
attributes_array: list[GltfAttribute | None] = [
mesh.points,
mesh.normals,
mesh.uvs,
mesh.batchids,
]
attributes_array.extend(mesh.additional_attributes)
attributes_indices_by_name: dict[str, int] = {}
for attribute in attributes_array:
if attribute is None:
continue
attributes_indices_by_name[attribute.name] = len(gltf.accessors)
array_blob = prepare_gltf_component(
gltf,
attribute,
len(gltf_binary_blob),
)
gltf_binary_blob += array_blob
gltf_mesh = pygltflib.Mesh(name=mesh.name, extras=mesh.properties)
for primitive in mesh.primitives:
# deal with texture
if primitive.texture_uri:
# if we have a texture_uri, we need a material to bear it
if primitive.material is None:
primitive.material = pygltflib.Material()
_set_texture_to_primitive(gltf, primitive.material, primitive.texture_uri)
primitive.material.pbrMetallicRoughness.baseColorTexture.texCoord = (
attributes_indices_by_name.get("TEXCOORD_0")
)
# deal with material
gltf_primitive = _create_gltf_primitive(gltf, primitive)
gltf_mesh.primitives.append(gltf_primitive)
# all primitive shares the same attributes. What they take is determined by the triangles
# we need to do that because the spec mandates that all attribute accessors of a primitives have the same count
# this is efficient because we store the attributes data only once
for name, index in attributes_indices_by_name.items():
setattr(gltf_primitive.attributes, name, index)
# triangles
if primitive.triangles is not None:
gltf_primitive.indices = len(gltf.accessors)
indice_blob = prepare_gltf_component(
gltf,
primitive.triangles,
len(gltf_binary_blob),
pygltflib.ELEMENT_ARRAY_BUFFER,
)
gltf_binary_blob += indice_blob
gltf.meshes.append(gltf_mesh)
gltf.set_binary_blob(gltf_binary_blob)
[docs]
def prepare_gltf_component(
gltf: pygltflib.GLTF2,
attribute: GltfAttribute,
byte_offset: int,
buffer_view_target: int = pygltflib.ARRAY_BUFFER,
) -> bytes:
array = attribute.array
array_blob = array.flatten().tobytes()
# note: triangles are sometimes expressed as array of face vertex indices, but from the gltf point of view, it is a flat scalar array
count = (
array.size if attribute.accessor_type == pygltflib.SCALAR else array.shape[0]
)
buffer_view = pygltflib.BufferView(
buffer=0, # Everything is stored in the same buffer for sake of simplicity
byteOffset=byte_offset,
byteLength=len(array_blob),
target=buffer_view_target,
)
gltf.bufferViews.append(buffer_view)
accessor = pygltflib.Accessor(
bufferView=len(gltf.bufferViews) - 1,
componentType=attribute.component_type,
count=count,
type=attribute.accessor_type,
)
# min / max for positions, mandatory
if attribute.name == "POSITION":
accessor.min = np.min(attribute.array, axis=0).tolist()
accessor.max = np.max(attribute.array, axis=0).tolist()
gltf.accessors.append(accessor)
return array_blob
