What are .lwo and .lws files? LightWave 3D, and opening them on a Mac

The .lwo object

An .lwo file is binary and built on Electronic Arts' EA IFF 85 standard. It's made of chunks with four-letter names: PNTS holds the points, POLS the polygons, and SURF the surfaces with their colour and textures. An object can have several layers, each with its own pivot and, optionally, a parent layer. A single polygon can have up to 1023 vertices, and besides ordinary faces the file carries subdivision patches, curves and maps (UVs, vertex colours, bone weights). Texture images aren't inside it – only references to them.

The file has no unit; by convention, according to the specification, it's the metre. LightWave's coordinates are left-handed: X to the right, Y up and Z forward. A program reading .lwo has to flip the Z axis, or the model comes out mirrored. The Assimp library did that in my test: a triangle at Z = 1 in the file ended up at Z = −1.

Three generations: LWOB, LWO2 and LWO3

Terminal tells you which generation you have:

head -c 12 model.lwo | tail -c 4

It prints LWOB, LWO2 or LWO3. For my test files, file said it too: IFF data, LWO2 3-D object.

Few programs cope with LWO3. Okino recommends re-saving files from LightWave 2017 and later in "LightWave 2015" format, which is LWO2. LightWave does that with Export LightWave 2015 Object. According to the LightWave 2024 help, though, the PBR material node doesn't carry over into LWO2.

An .lws scene needs its objects

A scene is readable text. This is how the one I wrote for testing starts:

LWSC
3

FirstFrame 1
LastFrame 60
FrameStep 1
FramesPerSecond 30

LoadObjectLayer 1 Objects/cube.lwo

LWSC and 3 are the header and the format version. LoadObjectLayer loads the first layer of the cube.lwo object, and the motion keyframes follow. The scene holds no objects, images or plug-ins – it only refers to them by path. According to the specification, the path is relative to the content directory, which the user sets in LightWave and which isn't written in the scene. It usually has Objects, Scenes and Images subfolders.

That's why a scene so often opens empty. Sending only the .lws file, renaming an object or moving it somewhere else is enough. Send the whole content folder, or let LightWave pack the scene with everything it needs using Package Scene.

In my test, Assimp found the objects when they were next to the scene, in an Objects folder next to it, or in an Objects folder one level up, beside the Scenes folder. A scene with a missing object loaded without a single mesh.

Where LightWave came from

LightWave came out at NewTek in 1990, originally as part of the Video Toaster for the Amiga. It has been sold on its own since 1994. It was strongest in TV effects: Babylon 5, Star Trek: Voyager and Battlestar Galactica used it. After Vizrt bought NewTek, development stopped in 2020. In April 2023 a new company, LightWave Digital, bought the program and restarted development. LightWave 2026 came out in June 2026 for Windows and macOS 14.1 and later, and a new licence costs £795.

The Doom 3 engine read .lwo files too – its released source code contains an LWO reader. And NASA still publishes several of its satellites as .lwo files.

How to open LWO on a Mac

macOS doesn't know LightWave. On macOS 27.0.1 it has no file type for .lwo or .lws, the Model I/O framework doesn't load them, and neither Preview, Quick Look nor the Finder shows them.

• [LightWave 3D](https://www.lightwave3d.com/) runs on the Mac too, but it's paid.
• [Blender](https://www.blender.org/) could import LWO by itself up to version 2.79. Today there's the third-party blender-import-lwo add-on, which reads LWOB and LWO2 and is tested with Blender 3.3 to 4.5. It doesn't handle LWO3 or .lws scenes yet.
• Preview3D, my app, opens .lwo files on a Mac in its window, in Quick Look and as Finder thumbnails. On iPad, iPhone and Apple Vision Pro too.

Preview3D reads LightWave through the Assimp library. I tried it in the same build the app uses, with LWO2 and LWOB files I made from the specification. It opened an object with several layers, polygons with more than four vertices, and an object with 72,900 points. According to its source code, Assimp reads LWO3 as well, but I haven't tried it with a real LWO3 file. The app shows the geometry in one plain colour: it doesn't use the file's surfaces or textures. Model info has the dimensions in the file's units and the triangle count, plus a mesh check. On iPad and iPhone it stands the model on your desk in AR, fitted to the desk.

Preview3D lists .lws scenes among its supported types as well. I haven't yet checked whether the app, inside the macOS sandbox, can reach the objects next to a scene, though. So open the .lwo files directly for now.

Converting LWO to STL or OBJ

On a Mac, Preview3D converts from File → Export model as… (⌥⌘E) to STL, OBJ or PLY, without uploading anything. Surfaces, textures, maps and layers are dropped, and the model is saved as one mesh. And mind the units: LightWave works in metres by convention, but a slicer usually takes the numbers in an STL as millimetres. If the model looks tiny in the slicer, scale it up 1000×.

Common questions

What is an .lwo file?

An object from LightWave 3D: a mesh with surfaces, layers and maps, stored in the binary IFF format.

What is an .lws file?

A LightWave text scene. It places .lwo objects, adds cameras, lights and bones, and stores their motion. The objects aren't in it, only references to them.

Why did my .lws scene open empty?

The .lwo objects it refers to are missing or somewhere else. Send the whole content folder with its Objects and Scenes subfolders, or pack the scene with Package Scene.

How do I tell whether I have LWO2 or LWO3?

In Terminal, head -c 12 model.lwo | tail -c 4 prints LWOB, LWO2 or LWO3.

Does a Mac open .lwo without another app?

No. macOS 27 has no file type for LightWave, and neither Preview nor Quick Look shows it.

How do I convert LWO to OBJ or STL?

On a Mac, in Preview3D with File → Export model as…, or in Blender with the LWO add-on. Then check the size in the slicer.

Related pages

• The .3ds file – the format of 3D Studio, which came out the same year
• The .obj file – the format LightWave objects are most often converted to
• The .stl file – the printing format

Sources

• LightWave SDK: LWO2 objects – chunks, coordinates, units, 1023 vertices
• LightWave SDK: LWSC scenes – file references, the content directory
• LightWave Digital: a new owner (2023) – history
• CG Channel: LightWave 2026 – system requirements and price
• LightWave 2024: Export LightWave 2015 Object
• Okino: LightWave import – older limits, LightWave 2017 and later
• blender-import-lwo – the Blender add-on
• Assimp: reading LWO and LWS
• NASA 3D Resources – satellites as .lwo files
• Doom 3 source code: the LWO reader

Have old LightWave objects or scenes – from TV work or Doom 3 mods, say – that wouldn't open on your Mac? Write to me at apps@xfanta.com and tell me which LightWave version they came from.