3D CAD Converter

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---
name: contenta-cad
description: Convert 3D CAD and mesh files with the 3D CAD Converter CLI (cadconvert). Use when the user asks to convert STEP, IGES or BREP to STL, OBJ, 3MF, glTF/GLB, FBX, PLY or other formats, convert between mesh formats (including USD/USDZ and VRML input), change units, control mesh quality for 3D printing, reduce the polygon count of a mesh, set the up axis for game engines, inspect a 3D file, or batch-convert or watch a folder of CAD files.
allowed-tools: Bash
---

> **Requires 3D CAD Converter installed on this Windows PC** (download: https://www.contenta-software.com/3dcadconverter/download.php). The commands below run the app's command-line tool on the user's own computer, so they work in Codex and other local agents. In ChatGPT, which cannot run programs on the user's computer, use this skill to choose the right command and give it to the user to run.


# 3D CAD Converter

Use the `cadconvert` CLI (3D CAD Converter 1.0.27+, Windows). Default per-user install: `%LOCALAPPDATA%\Programs\CadConverter\cadconvert.exe`, on the user PATH. Check with `cadconvert --version` (it prints the build id after a `+`).

No `--json` flag; for structured results use the MCP server (`cadconvert serve`).

## Commands

```bash
cadconvert convert <input> [<output>] [-f <fmt>] [--quality P|N] [--angular RAD] [--up-axis y|z|unchanged] [--decimate R] [--units mm|cm|in|m|ft] [--repair] [--binary true|false]
cadconvert batch <dir> [<outdir>] [-f stl] [-r] [-w N] [same conversion options]
cadconvert watch <dir> [<outdir>] [-f stl] [same conversion options]     # runs until Ctrl+C
cadconvert info <file>
cadconvert formats
cadconvert register -k <key> -e <email>      # exit 0 ok, 2 badly shaped key, 1 key rejected
```

- Paths can be positional or given with `-i`/`-o`. `-o` can be an existing folder (the file is named after the input).
- No output: `convert` writes next to the input with the `-f` extension (then `-f` is required); `batch` and `watch` write to `<input>_converted` next to the input folder.
- `-f` on `convert` defaults to the output extension; `batch` and `watch` default to `stl`. A `-f` that contradicts the output extension exits 2 (leave `-f` out to take it from the extension).
- `batch` is recursive by default; `-w` defaults to the number of logical processors.

## Mesh quality (STEP/IGES/BREP sources only)

`--quality` (same option as `--tessellation`) takes a preset or a linear deflection in mm. `--angular` is in **radians** and defaults to the preset's value (0.5 with a numeric deflection).

| Preset | Linear | Angular |
|--------|--------|---------|
| draft | 1.0 | 5.0 |
| standard (default) | 0.1 | 0.5 |
| fine (smooth curves, 3D printing) | 0.01 | 0.1 |
| ultrafine (`ultra` also works) | 0.001 | 0.05 |

Finer settings make much larger files: on a small test part, fine produced about 12x the triangles of standard. Mesh-to-mesh conversions ignore these options.

## Units

Sources that declare a unit are read at their true size, converted to mm, then written in `--units` (mm when left out):

- STEP, IGES: the file's unit. 3MF: `unit` attribute. glTF/GLB and VRML (`.wrl`, `.vrml`, `.wrz`): always metres (a 1 m VRML cube is 1000 mm). FBX: `UnitScaleFactor`. Collada: `<unit>` (metres when absent). USD/USDZ: `metersPerUnit` (centimetres when absent).
- BREP, STL, OBJ, PLY, OFF, X3D, AMF, DXF, DWG: no unit; the numbers are taken as mm. The CLI has no source-unit option.
- glTF, FBX and Collada outputs declare their unit and up axis; a glTF output opens at its true size in metres. VRML outputs declare their unit with a root `scale 0.001` (millimetre numbers, scaled to metres as the VRML specification requires).
- Since 1.0.25: glTF/GLB to STL/OBJ/3MF/PLY is 1000x larger than in 1.0.24 (true mm), any file to glTF opens at its true size, and a Blender cm FBX comes in 10x larger.

## Up axis, repair and polygon reduction

- `--up-axis y` for game engines, glTF and three.js; `z` for CAD and 3D printing. It starts from the up axis the source declares (USD, Collada, FBX, glTF, VRML). A STEP/IGES/BREP re-export is not rotated (the CLI prints a note).
- `--repair` repairs STEP/IGES/BREP surfaces before meshing (broken edges and faces, small gaps). It has no effect on mesh sources (STL, OBJ, PLY ...).
- `--decimate 0.25` (or `25%`) keeps about a quarter of the triangles. Mesh sources only: STL, OBJ, PLY, glTF/GLB, FBX, 3MF, Collada, OFF, VRML, X3D, AMF, DXF. STEP/IGES/BREP are not reduced; lower their `--quality` instead (draft is lightest). DWG and USD are not reduced. Meshes over 2,000,000 triangles are written unreduced. The desktop app has no reduction control.

## Formats

Write: stl, obj, ply, fbx, dae, 3mf, gltf, glb, wrl (vrml), x3d, off, step (.step/.stp), iges (.iges/.igs), brep.
Read only: amf, dwg, dxf, usd (.usd/.usda/.usdc, text or binary), usdz, and `.wrz` (gzipped VRML; `.wrl` and `.vrml` are read and written).

VRML input (1.0.27): VRML 2.0 and 1.0, read in metres and Y-up. Extrusion, line and point sets, Text, PROTO instances, textures, scripts and animation are not drawn (the message says so). Inline loads only relative local files; web, absolute and network addresses are refused with a warning.

BREP input means OpenCascade `.brep`/`.brp` only (not Parasolid `.x_t` or ACIS `.sat`). It has no unit, so it is read as mm, and it comes in as one merged solid without part names, colours or assembly tree.

## Examples (verified on 1.0.27, except the USD and USDZ lines)

```powershell
cadconvert convert model.step model.stl
cadconvert convert model.step -f glb
cadconvert convert model.step -o model_fine.stl --quality fine
cadconvert convert model.step -o model_fine.stl --tessellation 0.01 --angular 0.1
cadconvert convert model.step -o model_y.glb --up-axis y
cadconvert convert -i model.step -o model_in.obj --units in --repair
cadconvert convert tower.glb tower.stl                  # glTF metres -> true size in mm
cadconvert convert tower.glb tower_in.stl --units in
cadconvert convert tower_cm.fbx tower_fbx.stl           # Blender cm FBX -> mm
cadconvert convert scene.usdz scene.glb
cadconvert convert tower_yup.usda tower_z.stl --up-axis z
cadconvert convert scan.stl -o scan_light.glb --decimate 0.25
cadconvert convert -i model.stl -o model_ascii.stl --binary false
cadconvert convert part.brep part.step
cadconvert convert room.wrl room.stl                 # VRML is read in metres: a 1 m cube is 1000 mm
cadconvert convert model.step model.wrl
cadconvert batch -i .\cad-files -o .\meshes -f obj --quality fine
cadconvert batch .\cad-files
cadconvert info model.step
cadconvert info scene.usdz
cadconvert watch .\incoming -f glb --up-axis y
```

## Exit codes

0 success · 1 error (also a rejected license key) · 2 invalid arguments (also a `-f` that contradicts the output extension, an unknown extension, a file that is not a 3D format) · 3 file not found · 4 conversion failed (also `info` on a file with no readable geometry, and a `batch` with a failed file) · 5 not used (older versions: trial blocked a conversion).

## Guidelines

- Run `cadconvert info` first: it gives the declared unit (STEP, IGES, 3MF, FBX, Collada, USD; glTF and VRML are metres) and, for STEP/IGES/BREP/USD/VRML, the bounding box in mm. A file it cannot read is an error, not a table of zeros. STL, OBJ, PLY and OFF carry no unit and show Unknown.
- Use standard quality unless the user needs smooth curves (fine) or a quick, light preview (draft).
- To shrink a mesh file, use `--decimate`; to shrink a mesh made from STEP/IGES, use a coarser `--quality`.
- STL has no colors or materials; the CLI says so. Use 3MF, OBJ or GLB when color matters.
- glTF (`.gltf`) is JSON plus side files; GLB (`.glb`) is a single binary file and is easier to share.
- Trial: 10 conversions at full quality within 30 days of the first launch (plus 10 after the newsletter confirmation in the app). After that nothing is blocked: STEP/IGES/BREP to a mesh format is meshed at `draft` whatever `--quality` says, and every export carries a trial note (FBX gets draft only). The CLI prints `Buy:` and a link; `cadconvert register -k <key> -e <email>` removes it. In the MCP tool, paths must be absolute.