3D File Formats Compared: glTF/GLB, FBX, OBJ, and i3d

Four formats, four different jobs

The first time you download a 3D model, you run into a handful of file extensions that all mean "some kind of 3D," yet carry wildly different amounts of information. The four below show up most often, both in our own packages and across most other tools.

Part of the reason several formats coexist at all comes down to when each one was born. OBJ dates back to the 1980s, long before animation or PBR materials were even a consideration. FBX arrived in the 1990s to move data between animation packages. glTF, by contrast, is a deliberately young standard built for real-time use, and i3d was built by GIANTS specifically for its own engine rather than for general interchange. That history also explains why axis orientation and units differ from format to format: a real industry-wide standard for that only arrived with glTF, and everything older simply followed whatever the exporting software assumed.

glTF and GLB

glTF (GL Transmission Format) is an open standard from the Khronos Group, the same organization behind OpenGL and Vulkan. According to the official specification, glTF 2.0 locks in both the coordinate system, Y-axis up, and the unit, meters, and ships with a defined PBR material model, the so-called metallic-roughness model. GLB is the binary version of the same format: geometry, materials, textures, and animation data all live together in a single file, which makes sharing far simpler since no separate texture files need to travel alongside it.

FBX

FBX (Filmbox) is a proprietary format owned by Autodesk, originally created by Kaydara. It carries geometry, materials, and above all animation and skeletons, which is exactly why it became the go-to exchange format between different 3D applications, from character rigs to simple props. One recurring snag is units: Autodesk's own FBX exporter documentation notes that saving through MotionBuilder automatically converts values to centimeters, while other tools work in meters. Because FBX doesn't lock in a single fixed unit system and instead depends on whichever software exported it, that's one of the most common sources of errors when a file moves between programs. Unlike glTF, FBX also has no single binding specification for PBR materials, so each program brings its own idea of material channels along on export.

OBJ and MTL

The Wavefront OBJ format is one of the oldest widely-used 3D formats, and according to Autodesk's own 3ds Max documentation, it stores exclusively geometry descriptions, while the companion MTL file carries the material data. Godot's official documentation puts the practical reality bluntly: OBJ and MTL are supported, but "pretty limited," with no support for pivots, skeletons, animation, or PBR materials. That's often fine for a single, static object with a simple material, but not much beyond that. It's also worth knowing that an OBJ file without its matching MTL file still shows the raw geometry, just with no material at all, usually as a flat gray object — a frequent point of confusion when someone sends an OBJ file and forgets the MTL.

AI-generated

i3d (GIANTS)

The i3d format is the GIANTS Editor's native scene format and, by extension, the format behind Farming Simulator 25. According to the official GDN documentation, I3D is an XML-based file format with its own XML schema. A valid i3d file can contain up to seven parts: textures, materials, shapes, dynamics, scene graph, animation, and user data, and depending on the application, individual parts can be left out. Per GDN, the format uses a right-handed coordinate system and supports animation sets, keyframes, and morph targets alongside geometry and materials. Unlike glTF or FBX, almost nobody writes an i3d file by hand or edits one directly as text: it comes out of the official GIANTS exporter plugins for Blender or Maya.

Side-by-side comparison

Opening a GLB file on Windows

For GLB files, the 3D Viewer app from the Microsoft Store used to be the obvious route on Windows, since it effectively favored GLB anyway: every other imported format got converted to glTF internally before it was even displayed. Per Microsoft's own documentation on deprecated Windows features, Microsoft marked 3D Viewer deprecated in February 2026 and removed the app from the Microsoft Store on 1 July 2026. Existing installations keep working, per Microsoft, but can no longer be freshly downloaded after that date; as a viewing-only replacement, Microsoft points to the web-based Babylon.js Sandbox on that same page. If you need to actually work on the model, say to adjust materials, you're better off opening it directly in a free tool like Blender, which imports GLB natively and doesn't depend on the Windows-native viewer at all.

Opening an FBX file on Windows

FBX needed extra caution already, and 2026 added a second reason. Per Microsoft's official support page, 3D Viewer's FBX support was disabled by default back in February 2024 following a security vulnerability; trying to open an FBX file since then produces a message saying FBX files aren't supported by default. In an existing install, Microsoft's documentation says you could re-enable it through the app's settings and the "Open FBX Files" toggle. The bigger picture has since changed, though: Microsoft marked 3D Viewer itself deprecated in February 2026 and removed the app from the Microsoft Store on 1 July 2026, so it can't be installed on a new device at all anymore. For most people, the simpler route stays opening the file directly in Blender, which has shipped FBX import for years, runs independently of the Windows-native viewer, and needs no setting changed at all.

AI-generated

Which format fits which software

For the GIANTS Editor and Farming Simulator 25, there's no way around i3d, produced through the official exporter plugins from Blender or Maya. FBX or OBJ can't be imported directly.

In Unity, FBX and OBJ are both officially documented as natively supported formats, alongside DAE, 3DS, and DXF. glTF isn't listed as a core format in Unity's classic manual and needs an additional package.

In Godot, the official documentation explicitly recommends glTF 2.0 as the preferred format, fully supports both its text and binary (GLB) variants, and imports .blend files by quietly calling Blender itself in the background. FBX has also been on Godot's official format list since Godot 4.3, by default through the built-in ufbx library with no extra install required; Godot's own documentation still recommends reaching for one of the other listed formats where that's an option.

Blender, for its part, reads and writes practically all four formats, which is exactly why it works so well as a central hub whenever a model needs to move between different programs.

What's inside our own 3D model packages

We ship our 3D models in two separate package parts, because no single format serves every target program equally well. The GIANTS part contains pure i3d: shapes with a collision box, no placeable wrapper, meant to be built into your own mod i3d, plus the matching textures already converted to DDS in the formats the GIANTS pipeline expects. The second part covers everything else and ships as a .blend file with textures packed in, an .fbx with textures in a companion .fbm folder, and a separate .gltf with its own .bin file and a textures folder. So anyone not working in the GIANTS Editor, but building instead in Blender, Unity, or Godot, finds a properly prepared variant for that exact program in the same download, with no format conversion needed on their end.

That split follows the same logic as the comparison table above: the GIANTS Editor only gets i3d, because it simply can't read anything else. Every other program gets more than one option, since Godot's own docs favor glTF even though it also reads FBX natively since version 4.3, while Unity supports both out of the box.

AI-generated

The short version: what to try first

When in doubt, a simple order of preference covers most cases: for the GIANTS Editor and FS25, always i3d through the official exporter plugins; for everything else, try glTF/GLB first if the target software supports it, since units and axes are locked in by the spec and cause the fewest surprises. Reach for FBX once animation, a skeleton, or a program without glTF support enters the picture. OBJ stays the fallback for a single, static object when nothing else is available.

Common problems