Export checklist

An export checklist is a short list you run through every time an asset leaves your modeling tool. Most import problems (wrong size, lying on its side, black patches, missing collision) come from a handful of settings, and a checklist catches them before a teammate does.

This page is a starting checklist built from engine documentation and published export guides. Adapt it, write your team's version on one page, and keep it next to your naming conventions and art bibles and style guides.

#Before you start

Know your target. Each engine expects something different:

See units, scale and axes and coordinate systems and handedness for the background.

#The checklist

#1. Scale

• Model at real-world size. Unity's "physics and lighting systems expect 1 meter in the game world to be 1 unit in the imported Model file" (Unity 6.6 Manual: Preparing your model files for export). Godot's physics is tuned for metres too (Godot Engine 4.5 Documentation: Introduction to 3D).
• Check for a centimetre and metre mismatch in Unreal. Blender works in metres and Unreal in centimetres, so a mesh can import 100 times too large or small; check that the Scale in Unreal's Details panel reads 1, 1, 1, not 100 (Substack: Blender to UE5: the complete export pipeline).
• Know your importer's scale factor. Unity 2019.4 listed a default scale factor of 0.01 for .fbx but 1 for .blend (Unity 2019.4 Manual: Creating models outside of Unity).

#2. Axes and transforms

• Use known axis settings. Blender's FBX exporter defaults to Forward −Z and Up Y, and two export guides recommend leaving them alone for Unreal (Substack: Blender to UE5: the complete export pipeline; Cinevva: Blender to Unreal Engine Export Checklist…).
• Apply rotation and scale. In Blender, apply rotation and scale (Ctrl+A) so they reset before export (KatsBits Blender Knowledgebase: FBX rotation fix for Unity).
• For Unity, choose one fix for the Z-up to Y-up rotation: enable Bake Axis Conversion on import (Unity 2022.3 Manual: Model tab), or rotate and apply in Blender (KatsBits Blender Knowledgebase: FBX rotation fix for Unity).

#3. Pivot

• Put the pivot where the asset is placed or rotates from. For characters, one checklist says to model with the "feet on the floor at the origin" (Cinevva: Blender to Unreal Engine Export Checklist…). Doors pivot on the hinge; modular pieces on a grid corner. See pivot point and modular kits.

#4. Geometry health

• No flipped faces. Blender's Face Orientation overlay shows fronts "in blue" and backs "in red" (Blender 3.5 Manual: Viewport Overlays). See winding order and backface culling.
• No degenerate or non-manifold geometry. Run the 3D Print Toolbox or your tool's cleanup (Blender 3.6 Manual: 3D Print Toolbox). Unreal's importer can also remove degenerates, and Epic says "this option should be enabled" (Unreal Engine Documentation: FBX Import Options Reference). See degenerate geometry.
• Triangulate deliberately, or know that the importer will. See triangulation.

#5. Normals and tangents

• Export the normals you made. In Unreal's importer, Compute Normals means "Smoothing group and normal info is discarded" (Unreal Engine Documentation: FBX Import Options Reference). Use Import Normals, or Import Normals and Tangents, if you set up weighted (custom) normals or hard edges.
• Match the tangent basis to the bake. Unity's importer has a "Calculate Mikktspace" option (Unity Manual 2018.2: Model tab). See tangent space and MikkTSpace.
• Check the normal map's green channel against the engine: Unity uses Y+ (Unity Manual: Normal map); Unreal expects DirectX (Y−) (World of Level Design: DirectX vs OpenGL: Understanding, Using…). See normal map.

#6. UV channels

• UV0 for textures. Check it is the first channel.
• A lightmap UV if you bake lighting. Unity's Generate Lightmap UVs "Creates a second UV channel for the lightmap" (Unity Manual 2018.2: Model tab). Unreal's importer can generate "a set of unique, non-overlapping, UVs for use with static lighting" (Unreal Engine Documentation: FBX Import Options Reference). Or make your own; see lightmap UVs.

#7. Naming and collision

• Name to the house style, for example Epic's SM_ for static meshes (Unreal Engine 5.8 Documentation: Recommended Asset Naming Conventions in…). See naming conventions.
• Unreal collision: UCX_[RenderMeshName]_##, matching the render mesh name exactly (Epic Developer Community documentation: FBX Static Mesh Pipeline in Unreal Engine). One prop per file when it has custom collision, because "only the first mesh's collision will be imported" otherwise (Cinevva: Blender to Unreal Engine Export Checklist…).
• Godot collision: add -col, -convcol, -colonly or -convcolonly to node names (Godot Engine documentation: Node type customization using name suffixes). See collision meshes.

#8. LODs

• Decide where LODs come from. Unreal can generate them with LOD Group presets such as SmallProp, which reduce by 50% per step (Unreal Engine Documentation: Static Mesh Automatic LOD Generation). If you make them by hand, export them with the asset as your engine expects. See level of detail.

#9. Materials and textures

• Don't embed media. Unity advises against embedding textures in FBX, because it enlarges the project and slows import (Unity 6.6 Manual: Preparing your model files for export).
• One material slot per distinct material, named clearly. See draw calls.
• glTF only: set double-sided materials deliberately; when doubleSided is false, "back-face culling is enabled" (Khronos Group: glTF 2.0 Specification).

#10. Test the export

• Re-import it yourself. Unity's manual advises checking the exported file's size and re-importing it into your modeling software to confirm it looks right (Unity 6.6 Manual: Preparing your model files for export).
• Place it next to a reference (a mannequin, a 1 m cube, a door) in the engine and check size, rotation (0, 0, 0) and pivot.
• Look at it under light with the normal map applied: seams, black patches and inverted bumps show up immediately.

#Common mistakes

• Fixing problems in the engine. Rotating or scaling the imported asset hides the problem until the next re-import.
• Relying on old presets after a tool update. Exporters change; re-test after major updates.
• Several props with collision in one FBX for Unreal (Cinevva: Blender to Unreal Engine Export Checklist…).
• Discarding custom normals by leaving Compute Normals on (Unreal Engine Documentation: FBX Import Options Reference).

#Further reading and watching

• 3D file formats: FBX, glTF, OBJ and USD compared.