1. The basics

File → Export → glTF 2.0 (.glb/.gltf). In modern Blender (3.x+), this is built in.

2. The settings that matter

Format:           glTF Binary (.glb)     ← one file, smaller
Include:
  Limit to:       Selected + Visible      ← skip dev clutter
  Custom Properties: on if using IDs
  Cameras:        on if defining shots
  Punctual Lights: on for lights
Transform:
  +Y Up:          on  ← glTF convention
Data/Mesh:
  Apply Modifiers: on   ← bake subsurf, arrays, booleans
  UVs:             on
  Normals:         on
  Tangents:        on if using normal maps
  Vertex Colors:   on if you use them
  Compression:     Draco on (level 7 typical)
Data/Material:
  Images:          Automatic or Optimized
  Format:          AUTO   ← keeps PNG for alpha, JPG otherwise
Data/Animation:
  Export:          on
  Shape Keys:      on if you have them
  Bake All Actions:on for multi-take

3. The "Principled BSDF" shader rule

Connect your textures to Principled BSDF inputs:

• Base Color → baseColorTexture
• Metallic → metallicRoughnessTexture.b channel
• Roughness → metallicRoughnessTexture.g
• Normal → normalTexture (always through a Normal Map node)
• Emission + Emission Strength → emissiveTexture + factor
• Alpha → alpha channel of base color texture

4. Common pitfalls

5. Materials that DO port

6. Materials that DO NOT port

• Procedural nodes (Voronoi, Musgrave, etc.) — must be baked to a texture first.
• Mix shaders combining BSDFs (e.g., glass + diffuse mixed by Fresnel) — only one PBR BSDF gets through.
• Shader→Shader→... custom nodegraphs — baked or lost.
• Cycles-only ray features (Principled Volume, etc.) — ignored.

7. Multiple UV maps

glTF supports TEXCOORD_0, TEXCOORD_1. Map #1 is typically for lightmaps (after baking).

• Blender: UV menu → make a second UV. Auto-unwrap.
• Lightmap bake: Cycles → Bake → Diffuse + lightmap.
• In Three.js: set material.lightMap, ensure uv2 attribute exists.

8. Scale / unit gotchas

Blender default is meters. Mixamo FBX is often centimeters. If your character is 0.01m tall in Three.js, it's a cm→m conversion bug.

9. Export checklist (save as a text file)

[ ] Apply all modifiers (Ctrl+A on each)
[ ] Origin at feet / center of mass
[ ] Clear parents + clean transforms (Ctrl+A → Location/Rotation/Scale)
[ ] +Y Up checkbox on
[ ] Materials: Principled BSDF only
[ ] Textures packed OR relative paths
[ ] Armature in rest pose at frame 0
[ ] Actions named + marked Fake User (shield icon)
[ ] Bake All Actions on
[ ] Format: glb
[ ] Run gltf-transform inspect && validate after export

10. Python scripting

import bpy
bpy.ops.export_scene.gltf(
  filepath='/path/out.glb',
  export_format='GLB',
  export_apply=True,
  export_yup=True,
  export_animations=True,
  export_draco_mesh_compression_enable=True,
)

Run in Blender's script editor or via blender --background --python export.py for CI.

11. Takeaways

• Principled BSDF or nothing. Other shaders don't port.
• +Y Up is mandatory.
• Apply modifiers before export.
• Bake All Actions for animation.
• Always gltf-transform after. Never ship raw Blender output.