blender-export

The saved excerpt is a snapshot from review. The external source remains the complete and most current version.

---
name: blender-export
description: Export Blender scenes to glTF/GLB (web/AR), FBX (game engines), OBJ (universal), USD (VFX pipelines), STL (3D printing). Includes per-format settings, embed/unpack textures, axis conversion, polygon optimization (Decimate), and target-platform validation. Use whenever the user asks to "export this", "save as glTF / FBX / OBJ / STL / USD", "package for Unity / Unreal / Three.js / web / AR / 3D print", or any output format conversion. Make sure to use this skill even if the user does not say "export" — also covers "package this for the web", "make it work in Unity", "send to Unreal", "save for 3D printing".
when_to_use: Any export to a non-.blend format, packaging for game engines, web, AR, or 3D printing.
allowed-tools: Read Bash mcp__blender__execute_blender_code mcp__blender__get_scene_info mcp__blender__get_object_info
---

# Blender Export

Export to the right format with the right settings. Wrong format choice = days of debugging in the target platform.

## Format decision tree

```
Where is this going?
├── Web (Three.js, Babylon.js, model-viewer, AR Quick Look) → glTF / GLB
├── Game engine (Unity, Unreal, Godot)
│   ├── Animated/rigged → FBX (or glTF for modern engines)
│   └── Static → OBJ or FBX or glTF
├── Apple AR (USDZ) → USDZ (special, see Recipe 6)
├── 3D printing → STL (geometry only, must be watertight)
├── VFX pipeline (Maya, Houdini, Nuke) → USD
└── DCC roundtrip → FBX (industry standard)
```

**Quick rule for unknown target**: glTF / GLB. Open standard, modern, universally supported.

## Recipes

### Recipe 1 — glTF / GLB export (web / AR / general)

```python
import bpy

bpy.ops.export_scene.gltf(
    filepath='/tmp/output.glb',
    export_format='GLB',                 # single-file binary; preferred
    export_apply=True,                   # apply modifiers before export
    export_materials='EXPORT',
    export_image_format='AUTO',          # PNG; AUTO falls back to JPEG for opaque images
    export_yup=True,                     # Y-up convention (most engines / web expect this)
    export_animations=True,              # toggle off for static models
    export_morph=True,                   # shape keys
    export_skins=True,                   # armatures + weights
    export_normals=True,
    export_tangents=False,               # skip unless target uses tangent-space normals beyond standard
)

# Verify
import os
size_mb = os.path.getsize('/tmp/output.glb') / (1024 * 1024)
print(f"export:gltf {size_mb:.2f} MB")
```

**glTF caveats**:
- Only Principled BSDF materials export cleanly. Procedural shaders are dropped or simplified.
- Hard cap: 15 MB; soft target: 8 MB.
- No KTX2 / Draco compression (unless target supports those loaders).
- PNG textures only (max 1024×1024 typical).

### Recipe 2 — Decimate before export (if too large)

```python
import bpy

obj = bpy.data.objects['GEO-target']
bpy.context.view_layer.objects.active = obj

mod = obj.modifiers.new('Decimate', type='DECIMATE')
mod.ratio = 0.7    # keep 70% of faces; lower = more reduction
mod.use_collapse_degenerate = True
bpy.ops.object.modifier_apply(modifier=mod.name)

print(f"decimated:{obj.name} verts:{len(obj.data.vertices)}")
```

Then re-export. Iterate ratio until file size fits target.

### Recipe 3 — FBX export (game engines)

```python
import bpy

bpy.ops.export_scene.fbx(
    filepath='/tmp/output.fbx',
    use_selection=False,
    apply_unit_scale=True,
    apply_scale_options='FBX_SCALE_ALL',
    bake_space_transform=True,        # critical: applies rotation to mesh
    object_types={'MESH', 'ARMATURE', 'EMPTY'},
    use_mesh_modifiers=True,
    mesh_smooth_type='FACE',
    use_armature_deform_only=True,
    bake_anim=True,
    bake_anim_use_all_bones=True,
    bake_anim_use_nla_strips=True,
    bake_anim_use_all_actions=True,
    bake_anim_force_startend_keying=True,
    embed_textures=True,              # critical: embed textures into FBX
    path_mode='COPY',
    axis_forward='-Z',
    axis_up=