.3d File Extension
.3d mesh files contain, how their companion files work, and how Poly supports them. File extension details for .3d
Partial Support| File type | Unreal mesh data |
|---|---|
| MIME type | |
| Encoding | Binary Unreal mesh data; usually paired as _d.3d and _a.3d |
| Operating systems | Windows, macOS, Linux |
| Opens with | Unreal Engine 1 tools, Unreal mesh viewers |
| Poly support | Partial. Poly handles supported Unreal mesh data when its companion files are available. |
| Indexed by Poly | Yes. Poly indexes the filename and available scene metadata; it does not turn companion scripts into searchable 3D geometry. |
| Preview in Poly | Partial. A preview is available for supported mesh sets, not for an isolated companion file. |
| Poly agent | Partial. An optimized rendition of the 3D object or scene is provided to the agent when supported geometry is present. |
What kind of file is a .3d?
In the original Unreal mesh format, .3d is one half of a named asset set. The data file uses a suffix such as _d.3d; the animation file uses _a.3d, and a same-named .uc file describes the mesh and its animations. The format is binary and stores compressed vertices, triangles, texture coordinates, and surface flags.1
That naming convention matters. A single .3d file is often incomplete, and .3d is not the modern Unreal Engine asset container. Epic's current engine documentation describes imported meshes as becoming .uasset files, with FBX recommended for external static meshes.2
How do I open a .3d file?
Keep the _d.3d, _a.3d, .uc, textures, and matching directory structure together. Use a tool that explicitly supports the classic Unreal mesh format. If the set came from an Unreal Engine 1 project, open it with that project's tools or export it to glTF, GLB, or FBX. Renaming a file does not convert it.
Poly support for .3d
Poly can preview supported geometry from a complete asset set and provide an optimized rendition of the object or scene to the agent. It indexes filenames and available metadata. An isolated data or animation companion may remain stored and searchable by name without producing a standalone preview.
History and alternatives
The paired files reflect an older game asset workflow in which geometry, animation, and script metadata were separate. For current Unreal projects, use the engine's native assets or export through a current interchange workflow. glTF or GLB is convenient for portable viewing; FBX is commonly used when returning to Unreal.
Footnotes
- Epic Games. Unreal Engine directory structure. Epic documents the engine and game project asset directories; classic Unreal mesh sets should remain together with their project. ↩
- Epic Games. Importing Static Meshes. Epic recommends FBX for external 3D objects and documents Unreal's current asset workflow. ↩