Batch Convert OBJ and FBX to Optimized glTF

Converting 3D assets like OBJ and FBX into the web-standard glTF (or binary GLB) format is essential for modern real-time graphics pipelines. This article details the most effective command-line utilities available for automating and batch-processing conversions from OBJ and FBX to high-performance, optimized glTF files, along with compression strategies to minimize file sizes.

1. FBX2glTF

Developed by Meta, FBX2glTF is a dedicated, high-performance command-line tool built specifically to convert FBX files to glTF 2.0. It relies on the official Autodesk FBX SDK, ensuring high fidelity for meshes, materials, skeletal animations, and skinning data.

Key Features: Native support for binary glTF (.glb), embedded resources, and built-in Draco geometry compression.

Basic Command:

FBX2glTF -i model.fbx -o model.glb --draco

Batch Processing (Bash):

for file in *.fbx; do
  FBX2glTF -i "$file" -o "${file%.fbx}.glb" --draco
done

2. obj2gltf

Maintained by the Cesium team, obj2gltf is a Node.js-based command-line interface tailored specifically for converting OBJ files into glTF. It accurately parses .obj, .mtl, and associated textures, converting standard Blinn-Phong materials to glTF's PBR (Physically Based Rendering) metallic-roughness workflow.

Installation: npm install --global obj2gltf

Basic Command:

obj2gltf -i model.obj -o model.glb --binary

Batch Processing (Bash):

for file in *.obj; do
  obj2gltf -i "$file" -o "${file%.obj}.glb" --binary
done

3. Blender in Headless Mode

Blender provides built-in importers for both OBJ and FBX, along with the official glTF-Blender-IO exporter. You can run Blender without a user interface using the command line to execute Python batch scripts. This approach is ideal for handling mixed assets or complex scene hierarchies.

Execution Command:

blender --background --python convert_batch.py

Sample Python Script (convert_batch.py):

import bpy
import glob
import os

def process_files(extension, import_func):
    for filepath in glob.glob(f"*.{extension}"):
        bpy.ops.wm.read_factory_settings(use_empty=True)
        import_func(filepath=filepath)
        out_name = os.path.splitext(filepath)[0] + ".glb"
        bpy.ops.export_scene.gltf(
            filepath=out_name,
            export_format='GLB',
            export_draco_mesh_compression_enable=True
        )

process_files("fbx", bpy.ops.import_scene.fbx)
process_files("obj", bpy.ops.wm.obj_import)

4. Advanced Optimization: glTF-Transform

While converters can produce standard glTF files, achieving maximum compression requires dedicated optimization passes. glTF-Transform is the standard CLI utility for optimizing, inspecting, and manipulating glTF and GLB containers.

After converting your OBJ or FBX files to GLB, run them through glTF-Transform to compress textures and geometry.

Installation: npm install --global @gltf-transform/cli
Key Optimizations:
- Draco Compression: Reduces geometry size dramatically for static meshes.
```
gltf-transform draco input.glb output.glb
```
- Meshopt Compression: Faster decompression on mobile and web devices than Draco.
```
gltf-transform meshopt input.glb output.glb
```
- Texture Optimization: Resizes and converts textures to WebP or KTX2 Basis Universal formats.
```
gltf-transform webp input.glb output.glb
```
- Dedicated Optimize Pipeline: Runs deduping, pruning of unused nodes, and geometry quantization in a single pass.
```
gltf-transform optimize input.glb output.glb --compress meshopt
```

Complete Automated Pipeline Example

To handle batch conversion and optimization together in a single Bash pipeline:

#!/usr/bin/env bash

# 1. Convert all OBJ files
for f in *.obj; do
  [ -f "$f" ] || continue
  obj2gltf -i "$f" -o "temp_${f%.obj}.glb" --binary
done

# 2. Convert all FBX files
for f in *.fbx; do
  [ -f "$f" ] || continue
  FBX2glTF -i "$f" -o "temp_${f%.fbx}.glb"
done

# 3. Optimize all generated GLB files
for f in temp_*.glb; do
  [ -f "$f" ] || continue
  final_name="${f#temp_}"
  gltf-transform optimize "$f" "$final_name" --compress meshopt
  rm "$f"
done