3D File Formats: OBJ, STL, glTF, FBX and USDZ Compared

3D File Formats: OBJ, STL, glTF, FBX and USDZ Compared

The 3D world is fragmented into dozens of formats. Each was designed for a specific purpose: 3D printing, game engines, web, augmented reality, or industrial CAD.

Quick Comparison

OBJ — The Universal Classic

OBJ is plain text supported by virtually all 3D applications:

# Vertices
v 0.0 0.0 0.0
v 1.0 0.0 0.0
v 0.5 1.0 0.0

# UV texture coordinates
vt 0.0 0.0
vt 1.0 0.0

# Normals
vn 0.0 0.0 1.0

# Face (triangle: vertex/uv/normal)
f 1/1/1 2/2/1 3/3/1

Associated .mtl material file:

newmtl red_material
Kd 1.0 0.0 0.0
map_Kd color_texture.png

STL — 3D Printing Standard

STL only stores surface geometry as triangles. No colors, materials, or animation.

Exists in ASCII (readable) and binary (more compact, preferred) versions.

glTF / GLB — The "JPEG of 3D"

glTF 2.0 is the recommended format for web and modern engines:

• .gltf: JSON + external files (.bin + images)
• .glb: binary package (everything in one file)
• Built-in PBR materials
• Skeleton animation and morph targets
• GPU-efficient loading

import { GLTFLoader } from 'three/examples/jsm/loaders/GLTFLoader.js';

const loader = new GLTFLoader();
loader.load('/models/character.glb', (gltf) => {
    scene.add(gltf.scene);
    const mixer = new THREE.AnimationMixer(gltf.scene);
    mixer.clipAction(gltf.animations[0]).play();
});

FBX — Entertainment Industry Standard

Created by Autodesk, preferred for production pipelines (film, games):

• Full animation, bones, blend shapes support
• Native in Maya, 3ds Max, MotionBuilder
• Direct import in Unity and Unreal Engine
• Proprietary format (not fully open specification)

USDZ — Augmented Reality on Apple

Apple's format for AR Quick Look (iOS) and Apple Vision Pro:

• Based on USD (Universal Scene Description) by Pixar
• Compatible with AR Quick Look in Safari iOS without additional app
• Native 3D preview in macOS Finder

STEP — Precision CAD

STEP (ISO 10303) stores exact parametric CAD geometry:

• Used in engineering, architecture, manufacturing
• Interchange between SolidWorks, CATIA, AutoCAD, Fusion 360
• Not suitable for real-time rendering

Convert with Blender CLI

# FBX -> GLB
blender --background --python - << 'PYEOF'
import bpy
bpy.ops.import_scene.fbx(filepath="/path/model.fbx")
bpy.ops.export_scene.gltf(filepath="/path/model.glb", export_format='GLB')
PYEOF

# OBJ -> GLB
blender --background --python - << 'PYEOF'
import bpy
bpy.ops.import_scene.obj(filepath="/path/model.obj")
bpy.ops.export_scene.gltf(filepath="/path/model.glb", export_format='GLB')
PYEOF

# STL -> OBJ
blender --background --python - << 'PYEOF'
import bpy
bpy.ops.import_mesh.stl(filepath="/path/model.stl")
bpy.ops.export_scene.obj(filepath="/path/model.obj")
PYEOF

Convert with Open3D (Python)

import open3d as o3d

# Read OBJ or PLY
mesh = o3d.io.read_triangle_mesh("model.obj")
print(f"Vertices: {len(mesh.vertices)}, Triangles: {len(mesh.triangles)}")

# Save as STL / PLY
o3d.io.write_triangle_mesh("model.stl", mesh)
o3d.io.write_triangle_mesh("model.ply", mesh)

# Simplify mesh
simplified = mesh.simplify_quadric_decimation(target_number_of_triangles=10000)
o3d.io.write_triangle_mesh("model_simple.stl", simplified)

Repair STL with Trimesh

import trimesh

mesh = trimesh.load("model.stl")
print(f"Watertight (closed): {mesh.is_watertight}")
print(f"Volume: {mesh.volume:.2f} mm3")

trimesh.repair.fix_normals(mesh)
trimesh.repair.fix_winding(mesh)
mesh.fill_holes()
mesh.apply_scale(1000)  # meters to millimeters
mesh.export("model_repaired.stl")

When to Use Each Format

Convert Online

To convert between 3D formats without installing Blender, KaijuConverter enables direct browser-based conversion.

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