Export Pipelines

The execution model is in blender-core. Run blender-asset-qa (and blender-game-optimization for budgets) before exporting.

One call

scripts/export_asset.py -- --preset unreal_skeletal --objects SK_Hero --out //export/SK_Hero.fbx
scripts/export_asset.py -- --preset web --collection Export --out //export/scene.glb
scripts/export_asset.py -- --preset unity --objects SM_A SM_B SM_C --batch --out //export/x.fbx   # one file each, at origin

Presets: roblox, roblox_gltf, unity, unity_skeletal, unreal, unreal_skeletal, godot, web, gltf, usd. Pass any exporter kwarg with --set key=value. Every preset is tested with a round-trip that keeps scale and avoids a 100× armature scale.

Engine reference (load only the one you need)

• references/roblox.md: MeshParts, avatar bodies (R15), accessories, layered clothing cages, SurfaceAppearance, limits
• references/unity.md: FBX settings, Humanoid rigs, URP/HDRP maps, animation clips
• references/unreal.md: static/skeletal FBX, root bone, collision UCX, LODs, Nanite, ORM/DirectX
• references/godot-web.md: glTF/GLB, import suffixes, three.js/Babylon, compression, KHR extensions

Universal pre-export checklist

1. Scale: scene unit scale 1.0, objects at scale 1, rotation applied (except intentional object transforms). The presets handle unit conversion.
2. Pivot/origin where the engine expects it: props at the bottom-center, characters at the world origin between the feet, facing -Y (Blender front). Every preset converts that to the engine's forward.
3. Modifiers: the presets export the evaluated mesh. Mirror, bevel and weighted normals are kept; booleans become real geometry.
4. Normals: custom/weighted normals export. Smooth shading, plus hard edges marked sharp.
5. Triangulation: FBX presets triangulate (use_triangles) so the bake and engine tangents match. glTF always triangulates.
6. Materials: image-texture → Principled chains only, with names M_* and textures T_*. Procedural nodes don't export, so bake them first.
7. Armature: deform bones only, no leaf bones, rest pose = bind pose, 4 weights per vertex max, and the root at the origin.
8. Animation: one action per clip, named Rig_Clip. Bake constraints/IK to keys (blender-animation). FBX exports the active/NLA action per preset settings; glTF ACTIONS mode exports every action that has a slot for the armature.
9. Naming: unique, ASCII, no spaces. Engines key materials/meshes by name across reimports.

Format choice

Need	Format
Unity, Unreal (most stable for skeletal)	FBX
Godot, web, Roblox (supported), Unreal 5.x Interchange, Blender↔Blender	glTF 2.0 (.glb)
Film/VFX, Omniverse, Apple AR (.usdz), layout interchange	USD
Static geometry for printing/CAD	OBJ / STL (wm.obj_export, wm.stl_export)
Point caches / deforming sims	Alembic (wm.alembic_export)

Verify after export (required)

• The script returns ok, the file size, and for .glb a parsed summary (meshes, materials, images, animations, skins, tris, extensions). Compare it with what you expected.
• For FBX/USD: re-import into an empty scene (import_scene.fbx / wm.usd_import) and check dimensions, the armature scale (must be 1, not 100) and the action count.
• In the engine: scale against a reference (UE mannequin 180 cm, Unity capsule 2 m, Roblox character 5 studs), normals/smoothing, the normal map's green channel, and animation root motion.

Collection exporters (re-export in one click, 4.2+)

See blender-scene-setup: collection.exporters stores the format + settings per collection, and bpy.ops.wm.collection_export_all() re-exports everything.

Gotchas

• FBX use_tspace fails silently on n-gons. Triangulate first (the presets do).
• bake_space_transform (Apply Transform) is experimental. Use it for Unity static meshes only, never with armatures.
• glTF exports actions linked through slots/NLA. An action with no user on the armature is skipped (export_animation_mode options: ACTIONS, ACTIVE_ACTIONS, NLA_TRACKS, SCENE, BROADCAST).
• glTF needs image textures in PNG/JPEG/WebP. EXR/TIFF get converted (export_image_format).
• Linked library data exports fine, but make it local or override it if you need to modify it first.
• Shape keys: FBX exports them as blendshapes, glTF as morph targets (export_morph). Modifiers before the Armature modifier can block shape-key export in FBX (apply them first).