AI 3D Models in Unity: Import Settings for Any Generator

Which format to use

The decision mostly comes down to whether the asset will be animated.

FBX works in Unity without a package. For glTF, the manual pages are the Unity glTFast package (package id com.unity.cloud.gltfast, hosted on docs.unity3d.com/Packages), whose pages claim 100% glTF 2.0 compliance and list Universal, HDRP and Built-In pipelines. The 6.0.1 features page marks glTF-Binary (.glb) as supported for import and export; editor import is supported and export is flagged experimental with “Core features missing”. It states glTFast “requires Unity 2020.1 or newer”. The pages do not call it an “official” package in words; the Unity Technologies copyright and com.unity id are the evidence. The features page also lists the 6.0.1 limits: up to 4 joints and 4 weights per vertex. Playable API and Mecanim animation appear with only an issue link, not a supported mark. See GLB vs FBX vs OBJ for the format trade-off, and remember that exporting FBX from a generator does not mean the file is game-ready.

Setting up GLB with glTFast

Per the 6.0.1 installation page:

1. Open the Package Manager from the Window menu (the page writes “Windows > Package Manager”).
2. Select the Add (+) button and choose “Add + package by name”, as the page prints it.
3. In the Name field, enter com.unity.cloud.gltfast, then select Add.

After that, move glTF files into Assets as with other 3D formats. glTFast imports them “to native Unity prefabs and add[s] them to the asset database”. Two documented catches apply. For a .gltf with companion files, “the file names and relative paths cannot be changed, otherwise references may break”, which matters when a generator’s ZIP gets reorganized. And glTFast registers itself as the default importer for .gltf and .glb, so a second default importer produces an error beginning “Multiple scripted importers are targeting the extension ‘glb’”; the page’s recommended fix is to set the other importer as an alternative.

FBX Model tab settings

The manual’s Model tab lists these. Scene: Scale Factor, Convert Units, Bake Axis Conversion, Import BlendShapes, Import Visibility, Import Cameras, Import Lights, Preserve Hierarchy, Sort Hierarchy By Name. Meshes: Mesh Compression (Off, Low, Medium, High), Read/Write, Optimize Mesh, Generate Colliders. Geometry: Keep Quads, Weld Vertices (default on), Index Format (Auto, 16 bit, 32 bit), Normals (Import, Calculate, None), Tangents (Import, Calculate Legacy, Calculate Legacy - Split Tangent, Calculate Mikktspace, None), Swap UVs, Generate Lightmap UVs. Unity expects 1 meter = 1 unit.

Steps

1. Copy the .fbx (or .glb, with glTFast installed) into Assets.
2. Select it and open the Inspector’s Model tab.
3. Scale. Check Scale Factor and Convert Units against the unit convention. A quick reference is a default one-meter cube in the scene, as Neural4D’s guide also suggests. If the mesh arrives at the wrong size, fix it at the source where possible (see scale, pivot and axis fixes).
4. Mesh format. Index Format offers Auto (the default), 16 bit and 32 bit; the manual recommends 16 bit or Auto for bandwidth and memory reasons. Generator meshes can be very dense, so check the triangle count against your target with the polycount budget calculator before relying on defaults. Unity’s manual gives no recommended per-asset triangle figure in the pages we read.
5. Normals and tangents. Normals default to Import, and Unity calculates them if the file has none. Tangents can be imported or calculated, with Calculate Mikktspace the default when Normals is set to Calculate; the manual warns that a mesh with no tangents does not work with normal-mapped shaders. Which is right depends on how the textures were baked; we cannot say for any given generator.
6. Apply and inspect the result in the Preview pane and in a scene.

Materials tab

Unity’s Materials tab decides how a generator’s maps arrive, and it is where a “my model has no textures” problem usually gets solved. If the model has no material, Unity uses its diffuse default. If it has materials, Unity imports them as subassets.

• Material Creation Mode offers None, Standard (Legacy) and Import via MaterialDescription. The manual says MaterialDescription “provides more accurate results than previous import methods” and handles more material types. Neural4D’s guide recommends it for AI-tool FBX files with PBR maps; that is a vendor’s advice, not Unity’s.
• Location defaults to Use Embedded Materials. Extract Materials and Extract Textures buttons sit under it, so a generator’s embedded maps can be pulled out for editing.
• Remapped Materials lets you point to existing material assets, and Search and Remap finds them by name, using On Demand Remap’s Naming and Search properties.
• Search Textures Globally is legacy and off by default for new imports. The manual warns of “non-deterministic results when multiple textures share the same name”, which is a real risk if a batch of generated files all use similar texture names.

“New imports or changes to the original asset do not affect extracted materials”, so after regenerating and replacing a file, extracted materials stay as they were. To reimport them, remove the entries from the Remapped Materials list. Material appearance can also differ with the render pipeline; the glTFast table shows which material features each of Universal, HDRP and Built-In supports, and Neural4D’s guide attributes missing or broken results partly to shaders that do not match the pipeline.

Rig tab for generated characters

The Rig tab’s Animation Type offers None, Legacy, Generic and Humanoid. Unity picks one by default, “None” if it has never imported the file, so a generator’s rigged FBX still needs checking.

Humanoid needs “at least 15 bones organized in a way that loosely conforms to an actual human skeleton”. Choose Humanoid, leave Avatar Definition on Create From This Model, and open Configure. Bones Unity accepts appear green and the rest red. The Avatar window then provides the tools an auto-rig tends to need:

1. Mapping > Clear to reset any mapping Unity attempted.
2. Pose > Sample Bind-pose to approximate the original modeling pose.
3. Mapping > Automap to create a bone mapping from that pose.
4. Pose > Enforce T-Pose to return the model to the required T-pose, which is also the fix for the message “Character not in T-Pose”. If that does not work, rotate the remaining bones by hand.

The manual says a successful match “simply means that Unity was able to match all of the required bones”, so match optional bones and set a proper T-pose for better results. Naming helps too: “LeftArm” and “RightForearm” are the manual’s examples of clear names, which matters for a rig with generic bone labels.

Generic suits quadrupeds and creatures. It has no Avatar in the Humanoid sense, so you specify the Root node, which lets Unity blend clips that move the character through space.

Both types share Skin Weights: Standard (4 Bones) is the default, recommended for performance, and Custom allows 1 to 32 bones per vertex. Strip Bones removes bones with no weights from Skinned Mesh Renderers. Optimize Game Object stores the transform hierarchy in the Avatar and Animator for performance, and Extra Transforms to Expose keeps specific bones visible, such as a hand bone a weapon attaches to. To reuse one Avatar across characters with identical rigs, use Copy from Other Avatar. Where clips come from is covered in animating AI characters, and rig choice in the rigging section.

LODs

Unity’s import path: name meshes ExampleMeshName_LOD0, _LOD1, _LOD2, export FBX, and Unity creates a GameObject with an LOD Group automatically. No maximum is stated. In the LOD Group component, Fade Mode is Cross Fade, or Speed Tree for SpeedTree assets; Animate Cross-fading is on by default, otherwise Fade Transition Width runs from 0.0 to 1.0; thresholds are screen-height percentages from 100% to 0%. Making the levels is covered in LODs for AI models. The pages above are the 6.0 manual; we did not check whether later Unity versions add other LOD options.

Colliders

The Model tab’s Generate Colliders option attaches mesh colliders on import, and the manual says it is “useful for quickly generating a collision mesh for environment geometry, but should be avoided for geometry you’re moving”. For a Mesh Collider, the manual states convex colliders are limited to 255 triangles, and lists properties Convex, Is Trigger, Provides Contacts, Cooking Options (None, Everything, Cook for Faster Simulation, Enable Mesh Cleaning, Weld Colocated Vertices, Use Fast Midphase), Material and Mesh. Non-default Cooking Options require a readable mesh. The page says nothing explicit on non-convex colliders with a Rigidbody, so we do not state a rule; it does say that for moving or dynamic objects primitive colliders can be more efficient. A 255 triangle ceiling means a convex collider cannot follow the surface of a high-polygon generated mesh; see collision meshes for AI props.

What goes wrong

What is not verified

Unity-version differences in the FBX Importer UI after 6.0, glTFast behavior after 6.0.1 (the 6.10 export status was not checked), and everything about how particular generators’ files behave on import. Comparing imports across generators is a planned measurement, not a result. For the same exercise in other engines see Godot and Unreal; the hub is AI 3D models in game engines.