glTF-Transform: batch-optimize GLB assets for your game pipeline

Every game project eventually accumulates a folder of GLBs nobody has audited: oversized textures, duplicate accessors, uncompressed vertex data, untrimmed animations. glTF-Transform is the CLI and Node.js library that lets you fix all of it in one automated pass — no DCC tool, no manual re-export.

What glTF-Transform does — and why game pipelines need it

glTF-Transform is an open-source JavaScript library and CLI for reading, modifying, and writing glTF 2.0 and GLB files. Unlike Blender or Substance, it operates purely on the glTF document model: accessors, buffer views, meshes, materials, and extensions. That makes it lightweight, fast, and scriptable.

The key difference from other mesh optimizers: glTF-Transform is non-destructive to source files. It reads one GLB in, writes an optimized copy out. Run it against every asset at build time and keep clean source files in version control.

Core operations it covers:

• Draco mesh compression — reduce geometry transfer size by 60–90%
• KTX2 / Basis Universal texture compression — GPU-native formats for Unity, UE5, and Godot 4
• Dedup — strip duplicate accessors and buffer views (common in Blender multi-object exports)
• Prune — remove unused nodes, skins, animations, and materials
• Flatten — collapse scene hierarchy to reduce draw call overhead
• Resample — remove redundant animation keyframes without affecting playback
• Weld — merge nearby vertices below a threshold, useful before LOD generation

Installing and running the CLI on your asset folder

npm install -g @gltf-transform/cli
gltf-transform --version
# 4.x.x

Single-file optimization pass:

gltf-transform optimize input.glb output.glb \
  --texture-compress ktx2 \
  --texture-size 2048

Batch processing an entire folder:

for f in assets/raw/*.glb; do
  out="assets/optimized/$(basename "$f")"
  gltf-transform optimize "$f" "$out" \
    --texture-compress ktx2 \
    --texture-size 1024 \
    --draco
  echo "✓ $f → $out"
done

Tip: Always set --texture-size. Blender exports at full resolution by default — a 4096 albedo on a prop that never fills 256 px on screen is pure waste.

Key transforms every game dev should know

Engine-specific notes:

• Godot 4: skip Draco — Godot's built-in GLB importer does not support KHR_draco_mesh_compression at runtime. Use --texture-compress ktx2 only, or leave textures uncompressed and let Godot's import pipeline handle it.
• Unreal Engine 5: UE5 strips KTX2 and re-compresses textures internally. Run with --texture-compress none when targeting UE5; the dedup, prune, and flatten passes still reduce import time and version-control file sizes.
• Unity URP/HDRP: full support for both Draco and KTX2 via the Unity glTFast importer.

Automating GLB optimization in a CI/CD pipeline

For teams on GitHub Actions or any Node-based build, glTF-Transform installs as a dev dependency and integrates before the engine build step.

npm install --save-dev @gltf-transform/core @gltf-transform/extensions @gltf-transform/functions
npm install --save-dev draco3dgltf sharp

Minimal batch optimization script (scripts/optimize-assets.mjs):

import { NodeIO } from '@gltf-transform/core';
import { ALL_EXTENSIONS } from '@gltf-transform/extensions';
import { dedup, prune, resample, textureCompress } from '@gltf-transform/functions';
import draco3d from 'draco3dgltf';
import sharp from 'sharp';
import { glob } from 'glob';
import path from 'path';

const io = new NodeIO()
  .registerExtensions(ALL_EXTENSIONS)
  .registerDependencies({
    'draco3d.encoder': await draco3d.createEncoderModule(),
    'sharp': sharp,
  });

for (const src of await glob('assets/raw/**/*.glb')) {
  const dest = src.replace('assets/raw', 'assets/optimized');
  const doc = await io.read(src);
  await doc.transform(
    dedup(),
    prune(),
    resample(),
    textureCompress({ encoder: sharp, targetFormat: 'webp', resize: [1024, 1024] }),
  );
  await io.write(dest, doc);
  console.log(`✓ ${path.basename(src)}`);
}

GitHub Actions step:

- name: Optimize GLB assets
  run: node scripts/optimize-assets.mjs

Structure the repo so assets/raw/ holds artist-authored files and assets/optimized/ is a generated output never committed to git. Add assets/optimized/ to .gitignore and let CI regenerate it on every build. Artists push source GLBs freely; the pipeline handles optimization on every merge.

Verify the size reduction after a run:

du -sh assets/raw/ assets/optimized/
# assets/raw/     420M
# assets/optimized/  148M

Typical reduction on a mixed prop set: 40–70%, with no visible quality loss at in-game distances.

Start with production-ready GLBs from BitSoul's marketplace and run this pipeline on download. Every asset ships in GLB format — one gltf-transform optimize pass gives you engine-ready files with compressed geometry and GPU-native textures in seconds.

This post is part of the Ultimate Guide to Free 3D Game Assets — BitSoul's complete reference for formats, texturing, rigging, optimization, and engine integration.

Need drop-in assets for this workflow? Grab the 94-model Animal Bundle on the BitSoul marketplace and drop them straight into your project.