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pygltflib

This is a library for reading, writing and handling GLTF v2 files. It works for Python3.6 and above.

It supports the entire specification, including materials and animations. Main features are:

• GLB and GLTF support
• Buffer data conversion
• Extensions
• All attributes are type-hinted

Table of Contents

• Quickstart
  • Install
  • How do I...
    • Create an empty GLTF2 object?
    • Add a scene?
    • Load a file?
    • Load a binary GLB file?
    • Load a binary file with an unusual extension?
    • Load a B3DM file?
    • Access the first node (the objects comprising the scene) of a scene?
    • Create a mesh?
    • Convert buffers to GLB binary buffers?
    • Convert buffer to data uri (embedded) buffer?
    • Convert buffers to binary file (external) buffers?
    • Convert a glb to a gltf file?
    • Access an extension?
    • Add a custom attribute to Attributes?
    • Remove a bufferView?
    • Validate a gltf object?
    • Convert texture images inside a GLTF file to their own PNG files?
    • Convert texture images from a GLTF file to their own PNG files using custom file names?
    • Specify a path to my images when converting to files?
    • Export images from the GLTF file to any location (ie outside the GLTF file)?
    • Import PNG files as textures into a GLTF?
• About
  • Contributors
  • Thanks
  • Changelog
  • Installing
  • Source
• More Detailed Usage
  • A simple mesh
  • Reading vertex data from a primitive and/or getting bounding sphere
  • Create a mesh, convert to bytes, convert back to mesh
  • Loading and saving
  • Converting files
  • Converting buffers
  • Converting texture images
• Extensions
  • EXT_structural_metadata
• Running the tests

Quickstart

Install

pip install pygltflib

How do I...

Create an empty GLTF2 object?

from pygltflib import GLTF2

gltf = GLTF2()

Add a scene?

from pygltflib import GLTF2, Scene

gltf = GLTF2()
scene = Scene()
gltf.scenes.append(scene)  # scene available at gltf.scenes[0]

Load a file?

filename = "glTF-Sample-Models/2.0/AnimatedCube/glTF/AnimatedCube.gltf"
gltf = GLTF2().load(filename)

Load a binary GLB file?

glb_filename = "glTF-Sample-Models/2.0/Box/glTF-Binary/Box.glb"
glb = GLTF2().load(glb_filename)  # load method auto detects based on extension

Load a binary file with an unusual extension?

glb = GLTF2().load_binary("BinaryGLTF.glk")   # load_json and load_binary helper methods

Load A B3DM file?

.B3DM files are a deprecated format used by CesiumJS. They are a wrapper around a GLTF1 file. pygltflib only supports GLTF2 files. Please open an issue if this is important to you!

Access the first node (the objects comprising the scene) of a scene?

gltf = GLTF2().load("glTF-Sample-Models/2.0/Box/glTF/Box.gltf")
current_scene = gltf.scenes[gltf.scene]
node_index = current_scene.nodes[0]  # scene.nodes is the indices, not the objects 
box = gltf.nodes[node_index]
box.matrix  # will output vertices for the box object

Create a mesh?

Consult the longer examples in the second half of this document

• A simple mesh
• Reading vertex data from a primitive and/or getting bounding sphere
• Create a mesh, convert to bytes, convert back to mesh

Convert buffers to glb binary buffers?

from pygltflib import GLTF2, BufferFormat

gltf = GLTF2().load("glTF-Sample-Models/2.0/Box/glTF/Box.gltf")
gltf.convert_buffers(BufferFormat.BINARYBLOB)   # convert buffers to GLB blob

Convert buffer to data uri (embedded) buffer?

gltf.convert_buffers(BufferFormat.DATAURI)  # convert buffer URIs to data.

Convert buffers to binary file (external) buffers?

gltf.convert_buffers(BufferFormat.BINFILE)   # convert buffers to files
gltf.save("test.gltf")  # all the buffers are saved in 0.bin, 1.bin, 2.bin.

Convert a glb to a gltf file?

from pygltflib.utils import glb2gltf, gltf2glb

# convert glb to gltf
glb2gltf("glTF-Sample-Models/2.0/Box/glTF-Binary/Box.glb")

Access an extension?

# on a primitve
gltf.meshes[0].primitives[0].extensions['KHR_draco_mesh_compression']

# on a material
gltf.materials[0].extensions['ADOBE_materials_thin_transparency']

Add a custom attribute to Attributes?

# Application-specific semantics must start with an underscore, e.g., _TEMPERATURE.
a = Attributes()
a._MYCUSTOMATTRIBUTE = 123

gltf.meshes[0].primitives[0].attributes._MYOTHERATTRIBUTE = 456

Remove a bufferView?

gltf.remove_bufferView(0)  # this will update all accessors, images and sparse accessors to remove the first bufferView

Validate a gltf object?

from pygltflib import GLTF2
from pygltflib.validator import validate, summary
filename = "glTF-Sample-Models/2.0/AnimatedCube/glTF/AnimatedCube.gltf"
gltf = GLTF2().load(filename)
validate(gltf)  # will throw an error depending on the problem
summary(gltf)  # will pretty print human readable summary of errors
# NOTE: Currently this experimental validator only validates a few rules about GLTF2 objects

Convert texture images inside a GLTF file to their own PNG files?

from pygltflib import GLTF2
from pygltflib.utils import ImageFormat
filename = "glTF-Sample-Models/2.0/AnimatedCube/glTF/AnimatedCube.gltf"
gltf = GLTF2().load(filename)
gltf.convert_images(ImageFormat.FILE)
gltf.images[0].uri  # will now be 0.png and the texture image will be saved in 0.png

Convert texture images from a GLTF file to their own PNG files using custom file names?

from pygltflib import GLTF2
from pygltflib.utils import ImageFormat
filename = "glTF-Sample-Models/2.0/AnimatedCube/glTF/AnimatedCube.gltf"
gltf = GLTF2().load(filename)
gltf.images[0].name = "cube.png"  # will save the data uri to this file (regardless of data format)
gltf.convert_images(ImageFormat.FILE)
gltf.images[0].uri  # will now be cube.png and the texture image will be saved in cube.png

Specify a path to my images when converting to files?

By default pygltflib will load images from the same location as the GLTF file.

It will also try and save image files to the that location when converting image buffers or data uris.

You can override the load/save location using the 'path' argument to convert_images

from pygltflib import GLTF2
from pygltflib.utils import ImageFormat
filename = "glTF-Sample-Models/2.0/AnimatedCube/glTF/AnimatedCube.gltf"
gltf = GLTF2().load(filename)
gltf.images[0].name = "cube.png"  # will save the data uri to this file (regardless of data format)
gltf.convert_images(ImageFormat.FILE, path='/destination/') 
gltf.images[0].uri  # will now be cube.png and the texture image will be saved in /destination/cube.png

Export images from the GLTF file to any location (ie outside the GLTF file)?

from pygltflib import GLTF2
from pygltflib.utils import ImageFormat
filename = "glTF-Sample-Models/2.0/AnimatedCube/glTF/AnimatedCube.gltf"
gltf = GLTF2().load(filename)
gltf.export_image(0, "output/cube.png", override=True)  # There is now an image file at output/cube.png

Import PNG files as textures into a GLTF?

from pygltflib import GLTF2
from pygltflib.utils import ImageFormat, Image
gltf = GLTF2()
image = Image()
image.uri = "myfile.png"
gltf.images.append(image)
gltf.convert_images(ImageFormat.DATAURI)
gltf.images[0].uri  # will now be something like "data:image/png;base64,iVBORw0KGg..."
gltf.images[0].name  # will be myfile.png

More Detailed Usage Below

About

This is an unofficial library that tracks the official file format for GLTF2.

The library was initially built to load and save simple meshes but support for the entire spec, including materials and animations is pretty good. Supports both json (.gltf) and binary (.glb) file formats, although .glb support is missing some features at the moment.

It requires python 3.6 and above because it uses dataclasses and all attributes are type hinted. And f-strings, plenty of f-strings.

Check the table below for an idea of which sample models validate.

Questions? Contributions? Bug reports? Open an issue on the gitlab page for the project. We are very interested in hearing your use cases for pygltflib to help drive the roadmap.

Contributors

• Luke Miller
• Sebastian Höffner
• Arthur van Hoff
• Arifullah Jan
• Daniel Haehn
• Jon Time
• Laurie O
• Peter Suter
• Frédéric Devernay
• Julian Stirling
• Johannes Deml
• Margarida Silva
• Patiphan Wongklaew
• Alexander Druz
• Adriano Martins
• Dzmitry Stabrouski
• irtimir
• Florian Bruggisser
• Kevin Kreiser
• Neui
• Bernhard Rainer
• Philip Holzmann
• Gabriel Unmüßig
• Benjamin Renz
• Raphael Delhome

Thanks

pygltflib made for 'The Beat: A Glam Noir Game' supported by Film Victoria / VicScreen.

Changelog

• 1.16.2:

  • add documentation about b3dm file format
  • warn user if trying to load a GLTF v1 file (or any file outside the supported range) (Raphael Delhome)

• 1.16.1:

  • remove buffer data when converting images (Gabriel Unmüßig)
  • make validator accept animation channel sampler = 0 (Benjamin Renz)

• 1.16.0:

  • fix compile error by removing dead extension code
  • fix type hint in GLTF2.from_json() (Philip Holzmann)
  • add support for larger alignment for BIN-Chunk (for EXT_structural_metadata) (Philip Holzmann)

• 1.15.6:

  • fix buffer.uri and .bin file name mismatch when a glb is loaded from a path that contains additional period characters (Bernhard Rainer)

• 1.15.4:

  • fix buffer alignment by adding padding bytes in GLB export (Neui)

• 1.15.3:

  • Use sort_keys by default for deterministic output (Kevin Kreise)

• 1.15.2:

  • buffer.uri defaults to None (Kevin Kreise)

• 1.15.1:

  • Dataclasses install only required on python 3.6.x (cherry-pick from Saeid Akbari branch)
  • Removed deprecated AlphaMode after two years (use the pygltflib.BLEND, pygltflib.MASK, pygltflib.OPAQUE constants directly)
  • Removed deprecated SparseAccessor after two years (use AccessorSparseIndices and AccessorSparseValues instead)
  • Removed deprecated MaterialTexture after two years (use TextureInfo instead)
  • removed deprecated requirement from project

• 1.15.0:

  • Significantly improved save_to_bytes performance (20x faster) (Florian Bruggisser)
    • NOTE: Underlying binary blob is now mutable instead of immutable.

See [CHANGELOG.md] (https://gitlab.com/dodgyville/pygltflib/-/blob/master/CHANGELOG.md) for older versions

Installing

pip install pygltflib

or

py -m pip install pygltflib

Source

git clone https://gitlab.com/dodgyville/pygltflib

More Detailed Usage

Note: These examples use the official sample models provided by Khronos at:

https://github.com/KhronosGroup/glTF-Sample-Models

A simple mesh

from pygltflib import *

# create gltf objects for a scene with a primitive triangle with indexed geometry
gltf = GLTF2()
scene = Scene()
mesh = Mesh()
primitive = Primitive()
node = Node()
buffer = Buffer()
bufferView1 = BufferView()
bufferView2 = BufferView()
accessor1 = Accessor()
accessor2 = Accessor()

# add data
buffer.uri = "data:application/octet-stream;base64,AAABAAIAAAAAAAAAAAAAAAAAAAAAAIA/AAAAAAAAAAAAAAAAAACAPwAAAAA="
buffer.byteLength = 44

bufferView1.buffer = 0
bufferView1.byteOffset = 0
bufferView1.byteLength = 6
bufferView1.target = ELEMENT_ARRAY_BUFFER

bufferView2.buffer = 0
bufferView2.byteOffset = 8
bufferView2.byteLength = 36
bufferView2.target = ARRAY_BUFFER

accessor1.bufferView = 0
accessor1.byteOffset = 0
accessor1.componentType = UNSIGNED_SHORT
accessor1.count = 3
accessor1.type = SCALAR
accessor1.max = [2]
accessor1.min = [0]

accessor2.bufferView = 1
accessor2.byteOffset = 0
accessor2.componentType = FLOAT
accessor2.count = 3
accessor2.type = VEC3
accessor2.max = [1.0, 1.0, 0.0]
accessor2.min = [0.0, 0.0, 0.0]

primitive.attributes.POSITION = 1
node.mesh = 0
scene.nodes = [0]

# assemble into a gltf structure
gltf.scenes.append(scene)
gltf.meshes.append(mesh)
gltf.meshes[0].primitives.append(primitive)
gltf.nodes.append(node)
gltf.buffers.append(buffer)
gltf.bufferViews.append(bufferView1)
gltf.bufferViews.append(bufferView2)
gltf.accessors.append(accessor1)
gltf.accessors.append(accessor2)

# save to file
gltf.save("triangle.gltf")

Reading vertex data from a primitive and/or getting bounding sphere

import pathlib
import struct

import miniball
import numpy
from pygltflib import GLTF2

# load an example gltf file from the khronos collection
fname = pathlib.Path("glTF-Sample-Models/2.0/Box/glTF-Embedded/Box.gltf")
gltf = GLTF2().load(fname)

# get the first mesh in the current scene (in this example there is only one scene and one mesh)
mesh = gltf.meshes[gltf.scenes[gltf.scene].nodes[0]]

# get the vertices for each primitive in the mesh (in this example there is only one)
for primitive in mesh.primitives:

    # get the binary data for this mesh primitive from the buffer
    accessor = gltf.accessors[primitive.attributes.POSITION]
    bufferView = gltf.bufferViews[accessor.bufferView]
    buffer = gltf.buffers[bufferView.buffer]
    data = gltf.get_data_from_buffer_uri(buffer.uri)

    # pull each vertex from the binary buffer and convert it into a tuple of python floats
    vertices = []
    for i in range(accessor.count):
        index = bufferView.byteOffset + accessor.byteOffset + i*12  # the location in the buffer of this vertex
        d = data[index:index+12]  # the vertex data
        v = struct.unpack(">> from pygltflib import GLTF2
>>> filename = "glTF-Sample-Models/2.0/AnimatedCube/glTF/AnimatedCube.gltf"
>>> gltf = GLTF2().load(filename)
>>> gltf.scene
0

>>> gltf.scenes
[Scene(name='', nodes=[0])]

>>> gltf.nodes[0]
Node(mesh=0, skin=None, rotation=[0.0, -1.0, 0.0, 0.0], translation=[], scale=[], children=[], matrix=[], camera=None, name='AnimatedCube')
>>> gltf.nodes[0].name
'AnimatedCube'

>>> gltf.meshes[0].primitives[0].attributes
Attributes(NORMAL=4, POSITION=None, TANGENT=5, TEXCOORD_0=6)

>>> filename2 = "test.gltf"
>>> gltf.save(filename2)

GLB files

>>> from pygltflib import GLTF2
>>> glb_filename = "glTF-Sample-Models/2.0/Box/glTF-Binary/Box.glb"
>>> glb = GLTF2().load(glb_filename)
>>> glb.scene
0

>>> glb.scenes
[Scene(name='', nodes=[0])]

>>> glb.nodes[0]
Node(mesh=None, skin=None, rotation=[], translation=[], scale=[], children=[1], matrix=[1.0, 0.0, 0.0, 0.0, 0.0, 0.0, -1.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0], camera=None, name=None)

>>> glb.meshes[0].primitives[0].attributes
Attributes(POSITION=2, NORMAL=1, TANGENT=None, TEXCOORD_0=None, TEXCOORD_1=None, COLOR_0=None, JOINTS_0=None, WEIGHTS_0=None)

>>> glb.save("test.glb")

>>> glb.binary_blob()  # read the binary blob used by the buffer in a glb
<a>

Converting files

First method

from pygltflib import GLTF2

# convert glb to gltf
glb = GLTF2().load("glTF-Sample-Models/2.0/Box/glTF-Binary/Box.glb")
glb.save("test.gltf")

# convert gltf to glb
gltf = GLTF2().load("glTF-Sample-Models/2.0/Box/glTF/Box.gltf")
gltf.save("test.glb")

Second method using utils

from pygltflib import GLTF2
from pygltflib.utils import glb2gltf, gltf2glb

# convert glb to gltf
glb2gltf("glTF-Sample-Models/2.0/Box/glTF-Binary/Box.glb")

# convert gltf to glb
gltf2glb("glTF-Sample-Models/2.0/Box/glTF/Box.gltf", "test.glb", override=True)

Converting buffers

The data for a buffer in a GLTF2 files can be stored in the buffer object's URI string or in a binary file pointed to by the buffer objects' URI string or as a binary blob inside a GLB file.

While saving and loading GLTF2 files is mostly handled transparently by the library, there may be some situations where you want a specific type of buffer storage.

For example, if you have a GLTF file that stores all the associated data in .bin files but you want to create a single file, you need to convert the buffers from binary files to data uris or glb binary data.

There is a convenience method named convert_buffers that can help.

from pygltflib import GLTF2, BufferFormat

gltf = GLTF2().load("glTF-Sample-Models/2.0/Box/glTF/Box.gltf")
gltf.convert_buffers(BufferFormat.DATAURI)  # convert buffer URIs to data.
gltf.save_binary("test.glb")  # try and save, will get warning.
# Will receive: Warning: Unable to save data uri to glb format.

gltf.convert_buffers(BufferFormat.BINARYBLOB)   # convert buffers to GLB blob
gltf.save_binary("test.glb")

gltf.convert_buffers(BufferFormat.BINFILE)   # convert buffers to files
gltf.save("test.gltf")  # all the buffers are saved in 0.bin, 1.bin, 2.bin.

Converting texture images

The image data for textures in GLTF2 files can be stored in the image objects URI string or in an image file pointed to by the image objects' URI string or as part of the buffer.

While saving and loading GLTF2 files is mostly handled transparently by the library, there may be some situations where you want a specific type of image storage.

For example, if you have a GLB file that stores all its image files in .PNG files but you want to create a single GLTF file, you need to convert the images from files to data uris.

Currently converting images to and from the buffer is not supported. Only image files and data uris are supported.

There is a convenience method named convert_images that can help.

# embed an image file to your GLTF.

from pygltflib.utils import ImageFormat, Image
gltf = GLTF2()
image = Image()
image.uri = "myfile.png"
gltf.images.append(image)

gltf.convert_images(ImageFormat.DATAURI)  # image file will be imported into the GLTF
gltf.images[0].uri  # will now be something like "data:image/png;base64,iVBORw0KGg..."
gltf.images[0].name  # will be myfile.png

# create an image file from GLTF data uris

from pathlib import Path
from pygltflib.utils import ImageFormat, Image
gltf = GLTF2()
image = Image()
image.uri = "data:image/png;base64,iVBORw0KGg..."
image.name = "myfile.png"  # optional file name, if not provided, the image files will be called "0.png", "1.png"
gltf.images.append(image)

gltf.convert_images(ImageFormat.FILE)  # image file will be imported into the GLTF
gltf.images[0].uri  # will be myfile.png

assert Path("myfile.png").exists() is True

Extensions

The GLTF2 spec allows for extensions to added to any component of a GLTF file.

As of writing (August 2019) there are about a dozen extensions from Khronos and other vendors

In pygltflib, extensions are loaded as ordinary dict objects and so should be accessed like regular key,value pairs.

For example extensions["KHR_draco_mesh_compression"]["bufferView"] instead of extensions["KHR_draco_mesh_compression"].bufferView.

This allows future extensions to be automatically supported by pygltflib.

Extras should work the same way.

EXT_structural_metadata

The EXT_structural_metadata is a draft (August 2023) extension that defines a means of storing structured metadata within a glTF 2.0 asset.

EXT_structural_metadata imposes 8-byte binary data alignment requirements on an asset, allowing support for 64-bit data types while remaining compatible with the 4-byte alignments in the core glTF specification.

To support this meta extension, when pygltflib detects the presence of this extension in a GLTF2 object (for example, if EXT_structural_metadata is in self.extensionsUsed, self.extensionsRequired, or self.extensions) will pad chunks using 8-bytes instead of 4.

This alignment value (4 or 8 or indeed any power-of-two value) can be set manually using the set_min_alignment method.

Running the tests

Status of gltf-validator

Using sample models loaded and then saved using this library, here are validator reports (blank is untested). If available, The result of a visual inspection is in brackets next to the validator result.

Validator Status

Model	gltf to gltf	gltf to glb	glb to gltf	glb to glb
2CylinderEngine	passes	passes	passes	passes
AlphaBlendModeTest	passes	passes	passes	passes
AnimatedCube	passes	passes	no glb available	no glb available
AnimatedMorphCube	passes	passes	passes	passes
AnimatedMorphSphere	passes	passes	passes	passes
AnimatedTriangle	passes	passes	no glb available	no glb available
Avocado	passes	passes	passes	passes
BarramundiFish	passes	passes	passes	passes
BoomBox	passes	passes	passes	passes
BoomBoxWithAxes	passes	passes	no glb available	no glb available
Box	passes	passes	passes	passes
BoxAnimated	passes	passes	passes
BoxInterleaved	passes	passes		passes
BoxTextured	passes	passes
BoxTexturedNonPowerOfTwo	passes	passes
BoxVertexColors	passes	passes
BrainStem	passes	passes	passes
Buggy	passes	passes	passes
Cameras	passes	passes	no glb available	no glb available
CesiumMan	passes	passes
CesiumMilkTruck	passes	passes
Corset	passes	passes	passes	passes
Cube	passes	passes	no glb available	no glb available
DamagedHelmet	passes	passes	passes	passes
Duck	passes	passes	passes	passes
FlightHelmet	passes	passes	no glb available	no glb available
GearboxAssy	passes	passes
Lantern	passes	passes
MetalRoughSpheres	passes	passes
Monster	passes	passes
MultiUVTest	passes	passes
NormalTangentMirrorTest	passes	passes
NormalTangentTest	passes	passes		passes
OrientationTest	passes	passes
ReciprocatingSaw	passes	passes
RiggedFigure	passes	passes
RiggedSimple	passes	passes
SciFiHelmet	passes	passes	no glb available	no glb available
SimpleMeshes	passes	passes	no glb available	no glb available
SimpleMorph	passes	passes	no glb available	no glb available
SimpleSparseAccessor	passes	passes	no glb available	no glb available
SpecGlossVsMetalRough	passes	passes	passes	passes
Sponza	passes	passes	no glb available	no glb available
Suzanne	passes	passes	no glb available	no glb available
TextureCoordinateTest	passes	passes	passes	passes
TextureSettingsTest	passes	passes	passes	passes
TextureTransformTest	passes	passes	no glb available	no glb available
Triangle	passes	passes	no glb available	no glb available
TriangleWithoutIndices	passes	passes	no glb available	no glb available
TwoSidedPlane	passes	passes	no glb available	no glb available
VC	passes	fails	passes	passes
VertexColorTest	passes	passes	passes	passes
WaterBottle	passes	passes	passes	passes

utils.validator status

What does pygltflib.utils.validator test? NOTE: At the moment the validator raises an exception when an rule is broken. If you have ideas of the best way to return information on validation warnings/errors please open a ticket on our gitlab.

Rule	validator tests	exception raised
accessor.componentType must be valid	yes	InvalidAcccessorComponentTypeException
accessor min and max arrays must be valid length	yes	InvalidArrayLengthException
accessor min and max arrays must be same length	yes	MismatchedArrayLengthException
mesh.primitive.mode must be valid	yes	InvalidMeshPrimitiveMode
accessor.sparse.indices.componentType must be valid	yes	InvalidAccessorSparseIndicesComponentTypeException
bufferView byteOffset and byteStrides must be valid	yes	InvalidValueError
bufferView targets must be valid	yes	InvalidBufferViewTarget
all other tests	no

unittests

git clone https://github.com/KhronosGroup/glTF-Sample-Models
pytest test_pygltflib.py