GLB vs FBX vs OBJ for AI-Generated Models

What each format stores

glTF 2.0 / GLB. The Khronos spec (2.0.1) defines scenes, nodes, cameras, meshes, materials, textures, skins and animations. It is right-handed, +Y up, with linear units in meters and angles in radians. GLB packs the JSON and binary data into one file without base64; the spec notes base64 data URIs add about 33%.

FBX. A proprietary Autodesk format; the FBX SDK welcome page summary lists mesh, materials, animation, skeletal rigs, cameras and lights. A default unit was not confirmed from a dedicated Autodesk page, so we state none.

OBJ (with MTL). The Library of Congress description: geometry (polygons and freeform), with materials in a companion MTL file (mtllib, usemtl, newmtl, Ka/Kd/Ks, Ns, d, illum, map_Kd). No lights. The page discusses no units, skinning or animation, and PBR keywords (Ke, map_Ke, norm) have uneven support. We make no claim that OBJ does or does not carry a skeleton beyond what that page says.

How engines document them

Details by engine: Godot, Unity, Unreal, Roblox.

What generators offer

Export lists differ by vendor and sometimes by page. Meshy’s export guide lists GLB, FBX, OBJ, USDZ, STL, BLEND, 3MF and DXF (its docs landing and pricing pages list different sets), and says animated models export as FBX, GLB or USDZ only. It also says GLB embeds textures while FBX and OBJ keep them separate. 3D AI Studio’s FAQ lists GLB, FBX, OBJ, STL, USDZ, BLEND, 3MF, Collada and PLY. Rodin’s pages list overlapping formats with inconsistent lists, and Tripo’s consumer site could not be read; its API formats are documented. Sloyd’s pricing page names GLB and OBJ for its Guest tier. Whether two generators’ FBX files behave the same in an engine is not documented anywhere we read.

Choosing

• Static prop, Godot or Unreal: GLB is the documented first choice for Godot and an Interchange path for Unreal. In Unreal, check that the glTF route supports what you need.
• Static prop, Unity: FBX needs no package; GLB needs glTFast.
• Character with a rig: FBX or GLB, per what the rigging tool outputs. Check bones, weights and the 4-influences-per-vertex rule if the target is Roblox.
• Roblox: any of the three listed; the 20,000-triangle and texture limits apply regardless.
• Fallback, no rig: OBJ is listed by Unreal, Roblox and Godot (with limits), with materials in a separate MTL file that may need reattaching by hand.
• 3D printing: none of these is the print format. STL and 3MF are, and 3MF details are on multi-color and 3MF printing.

Format does not guarantee quality. A GLB can hold a million triangles; an FBX can have broken UVs. A file extension tells you nothing about game-readiness or printability.

What you set at import or export, by format

These are the documented settings that decide whether the file survives; each is from the cited page, accessed 2026-11-08.

Symptom table

Likely causes follow the documentation; none was reproduced on a generator’s output.

Handling in Blender

Many pipelines pass models through Blender, whose glTF 2.0 add-on has Export Format options (GLB, glTF Separate, glTF Embedded) and a Materials export setting; see importing AI models into Blender. The 5.2 manual lists the FBX importer options shown in the table; the File > Import menu label and the export option list were not on that page. Which importer is default in other Blender versions is not confirmed.

Still unknown

The actual behavior of each generator’s files on import into each engine. A round-trip test of materials, rig and scale per format is planned, not done. See the engine hub for the other guides.