fbx2stl  —  FBX / OBJ  →  STL  converter for Windows
neuralworkshk.com                                       version 1.0
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WHAT IT IS
  A single, self-contained program that converts FBX (and OBJ) models
  into binary STL. There is no file-size limit — it is built for the
  multi-GB files a web browser cannot open.

  Nothing to install. No Python, no Blender, no DLLs. One .exe.


HOW TO USE IT  (pick whichever is easiest)

  1. EASIEST — put fbx2stl.exe in the same folder as your model files
     and DOUBLE-CLICK it. It converts every .fbx and .obj in that
     folder, writing <name>.stl beside each one.

  2. Drag one or more model files onto fbx2stl.exe.

  3. From a command prompt:
        fbx2stl.exe model.fbx
        fbx2stl.exe model.fbx output.stl
        fbx2stl.exe a.fbx b.fbx c.obj


FIRST RUN: WINDOWS MAY WARN YOU
  Windows SmartScreen shows "Windows protected your PC" for any program
  downloaded from the internet that isn't code-signed.

      Click  "More info"  →  "Run anyway"

  If Windows blocks it entirely: right-click fbx2stl.exe → Properties →
  tick "Unblock" at the bottom → OK.


OPTIONS
  --scale N      Multiply every coordinate by N.
                 Example: a model in centimetres that you want in
                 millimetres →  fbx2stl.exe model.fbx --scale 10

  --keep-axes    Keep the file's own axes. By default the model is
                 converted to Z-up, which is what slicers and CAD
                 expect. (A file that is already Z-up is left alone.)

  --help         Show usage.


ABOUT UNITS
  The converter prints the units the FBX declares, e.g.
      file units: 1 unit = 0.01 m (cm)
  and writes the coordinates unchanged — the same thing assimp and
  other standard tools do. Slicers read STL as millimetres, so if the
  size comes out wrong, use --scale.


AFTER CONVERTING
  Drag the .stl into the online tool:
      https://neuralworkshk.com/apps/STLPartSeparator/

  That tool streams STL files, so multi-GB models load fine there —
  separate parts, measure weight, make a solid watertight body for
  3D printing, compare against reference images, and export.


HOW BIG A FILE CAN IT HANDLE?
  Tested on a 625 MB FBX (4,004,450 triangles): converted with the
  triangle count and geometry preserved exactly, using about 780 MB of
  memory — roughly 1.25× the input file. So a 1.5 GB FBX needs
  around 2 GB of free RAM.

  The STL it writes is streamed to disk as it goes, so output size is
  limited only by your free disk space.


TROUBLESHOOTING
  "no triangles found"
      The file has no mesh geometry (only cameras/lights/bones/curves).

  "failed to parse"
      The file may be a very old FBX version, or corrupt. Try
      re-exporting it from the program that made it, as FBX 2013 or
      newer, binary format.

  The model comes out the wrong size
      Use --scale (see ABOUT UNITS above).

  The model is lying on its side
      Try --keep-axes.
