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    glTF Pipeline

    License Build Status Coverage Status

    Content pipeline tools for optimizing glTF assets by Richard Lee and the Cesium team.

    This project is under active development, see the roadmap.

    gltf-pipeline can be used as a command-line tool or Node.js module.


    Clone this repo and install Node.js 6.x or later. From the root directory of this repo, run:

    npm install

    Command-Line Example:

    node ./bin/gltf-pipeline.js -i ./specs/data/boxTexturedUnoptimized/CesiumTexturedBoxTest.gltf -o output.gltf

    Compress textures to the dxt1 and etc1 formats

    node ./bin/gltf-pipeline.js -i ./specs/data/boxTexturedUnoptimized/CesiumTexturedBoxTest.gltf -o output.gltf --texcomp.dxt1.enable --texcomp.dxt1.quality=10 --texcomp.etc1.enable

    Command-Line Flags

    Flag Description Required
    --help, -h Display help No
    --input, -i input=PATH, Read unoptimized glTF from the specified file. ✅ Yes
    --output, -o output=PATH, Write optimized glTF to the specified file. No
    --binary, -b Write binary glTF file using KHR_binary_glTF extension. No, default false
    --separate, -s Write separate geometry/animation data files, shader files, and textures instead of embedding them in the glTF asset. No, default false
    --separateImage, -t Write out separate textures, but embeds geometry/animation data files and shader files in the glTF asset. No, default false
    --quantize, -q Quantize the attributes of this glTF asset using the WEB3D_quantized_attributes extension. No, default false
    --encodeNormals, -n Oct-encode the normals of this glTF asset. No, default false
    --compressTextureCoordinates, -c Compress the testure coordinates of this glTF asset. No, default false
    --removeNormals, -r Strips off existing normals, allowing them to be regenerated. No, default false
    --smoothNormals, -m If normals are missing, they should be generated with smooth normals. No, default false
    --faceNormals, -f If normals are missing, they should be generated using the face normal. No, default false
    --cesium Optimize the glTF for Cesium by using the sun as a default light source. No, default false
    --tangentsBitangents If normals and texture coordinates are given, generate tangents and bitangents. No, default false
    --stats Print statistics to console for input and output glTF files. No, default false
    --kmc.enable Materials should be expressed using the KHR_materials_common extension. If other kmc flags are enabled, this is implicitly true. No, default false
    --kmc.doubleSided Declares whether backface culling should be disabled. No, default false
    --kmc.technique The lighting model to use. No, default PHONG
    --ao.enable Bake ambient occlusion (to vertex data by default). If other ao flags are enabled, this is implicitly true. Advanced settings in lib/bakeAmbientOcclusion.js No, default false
    --ao.toTexture Bake AO to existing diffuse textures instead of to vertices. Does not modify shaders. No, default false
    --ao.groundPlane Simulate a groundplane at the lowest point of the model when baking AO. No, default false
    --ao.ambientShadowContribution Amount of AO to show when blending between shader computed lighting and AO. 1.0 is full AO, 0.5 is a 50/50 blend. No, default 0.5
    --ao.quality Quality to use when baking AO. Valid settings are high, medium, and low. No, default low
    --texcomp.<format>.enable Whether to compress textures with the given compressed texture format. If other texcomp.<format> flags are enabled, this is implicitly true. Multiple formats may be supplied by repeating this flag. Must be one of the following: pvrtc1, pvrtc2, etc1, etc2, astc, dxt1, dxt3, dxt5, crunch-dxt1, crunch-dxt5. Compressed textures are saved as Cesium and 3D Tiles specific metadata inside image.extras.compressedImage3DTiles. More details about texture compression in glTF here: No, unless other texcomp options are set.
    --texcomp.<format>.quality The compressed texture quality from 0 to 10. No, default 5
    --texcomp.<format>.bitrate The bitrate when using the pvrtc or astc formats. For pvrtc formats this value must be 2.0 or 4.0. No, default 2.0
    --texcomp.<format>.blockSize The block size for astc compression. Smaller block sizes result in higher bitrates. This value is ignored if options.bitrate is also set. Must be one of the following: 4x4, 5x4, 5x5, 6x5, 6x6, 8x5, 8x6, 8x8, 10x5, 10x6, 10x8, 10x10, 12x10, 12x12 No, default 8x8
    --texcomp.<format>.alphaBit Store a single bit for alpha. Only supported for etc2. No, default false

    Build Instructions

    Run the tests:

    npm run test

    To run ESLint on the entire codebase, run:

    npm run eslint

    To run ESLint automatically when a file is saved, run the following and leave it open in a console window:

    npm run eslint-watch

    Building for Cesium integration

    Some functionality of gltf-pipeline is used by Cesium as a third party library. The necessary files can be generated using:

    npm run build-cesium

    This will output a portion of the gltf-pipeline code into the dist/cesium folder, reformatted into AMD style for use with RequireJS and Cesium in the browser.

    Third-party tools

    This project bundles several native binaries for texture compression.

    On Linux you may need to install g++ 4.8 as some of the tools link to the libgcc and libstdc++ runtimes.

    Run the help command for each tool for a more detailed description of the supported command-line options.

    Building for other integration

    Some functionality of gltf-pipeline is used by other projects along with Cesium as a third party library. The necessary files can be generated using:

    npm run build-cesium-combine

    This will output a portion of the gltf-pipeline code into the dist/cesium-combined folder, reformatted into self-contained file. Currently, only files that have no other local dependencies are allowed.

    Running Test Coverage

    Coverage uses nyc. Run:

    npm run coverage

    For complete coverage details, open coverage/lcov-report/index.html.

    The tests and coverage covers the Node.js module; it does not cover the command-line interface, which is tiny.

    Generating Documentation

    To generate the documentation:

    npm run jsdoc

    The documentation will be placed in the doc folder.


    • To debug the tests in Webstorm, open the Gulp tab, right click the test task, and click Debug 'test'.
    • To run a single test, change the test function from it to fit.

    Deploying to npm

    • Proofread
    • Update the version in package.json to match the latest version in
    • Make sure to run the tests and ensure they pass.
    • If any changes are required, commit and push them to the repository.
    • Create and test the package.
    ## NPM Pack
    ## Creates tarball. Verify using 7-zip (or your favorite archiver).
    ## If you find unexpected/unwanted files, add them to .npmignore, and then run npm pack again.
    npm pack
    ## Test the package
    ## Copy and install the package in a temporary directory
    mkdir temp && cp <tarball> temp/
    npm install --production <tarball>
    node -e "var test = require('gltf-pipeline');" # No output on success
    # If module has executables, then test those now.
    • Tag and push the release.
      • git tag -a <version> -m "<message>"
      • git push origin <version>
    • Publish
    npm publish

    Contact @lilleyse if you need access to publish.


    Pull requests are appreciated! Please use the same Contributor License Agreement (CLA) and Coding Guide used for Cesium.


    This product includes components of the PowerVR Tools Software from Imagination Technologies Limited.



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