gltf-pipeline

glTF Pipeline

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

Supports common operations including:

• Converting glTF to glb (and reverse)
• Saving buffers/textures as embedded or separate files
• Converting glTF 1.0 models to glTF 2.0
• Applying Draco mesh compression

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

Getting Started

Install Node.js if you don't already have it, and then:

npm install -g gltf-pipeline

Using gltf-pipeline as a command-line tool:

Converting a glTF to glb

gltf-pipeline -i model.gltf -o model.glb

gltf-pipeline -i model.gltf -b

Converting a glb to glTF

gltf-pipeline -i model.glb -o model.gltf

gltf-pipeline -i model.glb -j

Converting a glTF to Draco glTF

gltf-pipeline -i model.gltf -o modelDraco.gltf -d

Saving separate textures

gltf-pipeline -i model.gltf -t

Using gltf-pipeline as a library:

Converting a glTF to glb:

const gltfPipeline = require("gltf-pipeline");
const fsExtra = require("fs-extra");
const gltfToGlb = gltfPipeline.gltfToGlb;
const gltf = fsExtra.readJsonSync("./input/model.gltf");
const options = { resourceDirectory: "./input/" };
gltfToGlb(gltf, options).then(function (results) {
  fsExtra.writeFileSync("model.glb", results.glb);
});

Converting a glb to embedded glTF

const gltfPipeline = require("gltf-pipeline");
const fsExtra = require("fs-extra");
const glbToGltf = gltfPipeline.glbToGltf;
const glb = fsExtra.readFileSync("model.glb");
glbToGltf(glb).then(function (results) {
  fsExtra.writeJsonSync("model.gltf", results.gltf);
});

Converting a glTF to Draco glTF

const gltfPipeline = require("gltf-pipeline");
const fsExtra = require("fs-extra");
const processGltf = gltfPipeline.processGltf;
const gltf = fsExtra.readJsonSync("model.gltf");
const options = {
  dracoOptions: {
    compressionLevel: 10,
  },
};
processGltf(gltf, options).then(function (results) {
  fsExtra.writeJsonSync("model-draco.gltf", results.gltf);
});

Saving separate textures

const gltfPipeline = require("gltf-pipeline");
const fsExtra = require("fs-extra");
const processGltf = gltfPipeline.processGltf;
const gltf = fsExtra.readJsonSync("model.gltf");
const options = {
  separateTextures: true,
};
processGltf(gltf, options).then(function (results) {
  fsExtra.writeJsonSync("model-separate.gltf", results.gltf);
  // Save separate resources
  const separateResources = results.separateResources;
  for (const relativePath in separateResources) {
    if (separateResources.hasOwnProperty(relativePath)) {
      const resource = separateResources[relativePath];
      fsExtra.writeFileSync(relativePath, resource);
    }
  }
});

A Note on resourceDirectory and allowAbsolute

If a resourceDirectory is not specified, the only possible paths in a glTF object are absolute. In the event processGltf is called without a resourceDirectory and the glTF references absolute paths, it will behave as if allowAbsolute is true, but also emit a warning if it's not. To get rid of this warning, add allowAbsolute: true to your options, e.g.,:

const options = {
  /*... */
};
const results = await processGltf(gltf, options);

should be changed to:

const options = {
  allowAbsolute: true,
  /*... */
};
const results = await processGltf(gltf, options);

Command-Line Flags

Flag	Description	Required
--help, -h	Display help	No
--input, -i	Path to the glTF or glb file.	:white_check_mark: Yes
--output, -o	Output path of the glTF or glb file. Separate resources will be saved to the same directory.	No
--binary, -b	Convert the input glTF to glb.	No, default false
--allowAbsolute, -a	Allow glTF files to refer to file URLs outside of their source path	No, default false
--json, -j	Convert the input glb to glTF.	No, default false
--separate, -s	Write separate buffers, shaders, and textures instead of embedding them in the glTF.	No, default false
--separateTextures, -t	Write out separate textures only.	No, default false
--stats	Print statistics to console for output glTF file.	No, default false
--keepUnusedElements	Keep unused materials, nodes and meshes.	No, default false
--keepLegacyExtensions	When false, materials with KHR_techniques_webgl, KHR_blend, or KHR_materials_common will be converted to PBR.	No, default false
--draco.compressMeshes, -d	Compress the meshes using Draco. Adds the KHR_draco_mesh_compression extension.	No, default false
--draco.compressionLevel	Draco compression level [0-10], most is 10, least is 0. A value of 0 will apply sequential encoding and preserve face order.	No, default 7
--draco.quantizePositionBits	Quantization bits for position attribute when using Draco compression.	No, default 11
--draco.quantizeNormalBits	Quantization bits for normal attribute when using Draco compression.	No, default 8
--draco.quantizeTexcoordBits	Quantization bits for texture coordinate attribute when using Draco compression.	No, default 10
--draco.quantizeColorBits	Quantization bits for color attribute when using Draco compression.	No, default 8
--draco.quantizeGenericBits	Quantization bits for skinning attribute (joint indices and joint weights) and custom attributes when using Draco compression.	No, default 8
--draco.unifiedQuantization	Quantize positions of all primitives using the same quantization grid. If not set, quantization is applied separately.	No, default false
--draco.uncompressedFallback	Adds uncompressed fallback versions of the compressed meshes.	No, default false
--baseColorTextureNames	Names of uniforms that should be considered to refer to base color textures when updating from the KHR_techniques_webgl extension to PBR materials.	No. (The defaults are not specified here)
--baseColorFactorNames	Names of uniforms that should be considered to refer to base color factors when updating from the KHR_techniques_webgl extension to PBR materials.	No. (The defaults are not specified here)

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 CesiumJS integration

Some functionality of gltf-pipeline is used by CesiumJS 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 for use with CesiumJS in the browser. Copy the files into Source/Scene/GltfPipeline/ in the cesium repository and submit a pull request.

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.

Contributions

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

Changelog

4.3.0 - 2025-07-10

• Backported support for KHR_materials_specular from CesiumJS #676