mesh-converter#

A static web app for converting meshes between formats: upload a mesh file, inspect it in an interactive 3D view (shaded, wireframe, shaded + wireframe, or points), and download it in a format of your choice. Formats differ in what they can store, and the UI shows exactly which attributes (normals, colors) would be dropped by a lossy conversion.

Conversion is powered by meshio running in the browser via Pyodide — no server, all mesh I/O happens client-side. The first visit downloads the Python runtime (~15 MB from the jsDelivr CDN, cached afterwards).

† HDF5-based formats need the h5py Pyodide package (~4 MB); it is loaded lazily the first time such a format is used, so the default footprint stays small.

✓ marks what this app preserves when writing the format: vertex normals map to each format's native representation (nx/ny/nz properties in PLY, vn lines in OBJ, a Normals point-data array elsewhere) and vertex colors likewise (red/green/blue in PLY, an RGB point-data array elsewhere). On import, quads and polygons are fan-triangulated; volume cells are skipped.

Some meshio formats are deliberately absent: ansys, cgns, su2, and ugrid cannot roundtrip their own output in meshio 5.3.5; exodus fails writing under wasm; flac3d holds volume cells only; wkt's reader hangs on non-toy meshes; tetgen spans two files; svg is write-only.

A built-in sample mesh (a rainbow torus with normals and vertex colors) is available from the UI for trying things out without a file, and examples/ holds it pre-exported in a few formats. An on-demand "estimate export sizes" action serializes the loaded mesh to every format in memory and shows the resulting file sizes in the format table and export dropdown.

A loaded mesh can be shared as a self-contained link: "Copy share link" packs the original uploaded file (byte-identical, in its original format) together with the chosen export format and view mode into the URL fragment — deflate-compressed and base64url-encoded after #share=. Nothing is uploaded; the data lives in the URL itself, so whoever opens the link sees the mesh and can download it in any format. Links are capped at 65,000 characters (roughly a 100–300 KB mesh file, depending on how well it compresses); beyond that the app says the mesh is too large to share by URL.

Development#

npm install
npm run dev      # local dev server
npm run build    # static build in dist/

Built with Vite, React, TypeScript, and three.js (react-three-fiber).

How it works#

• src/mesh/bridge.py runs inside Pyodide: it reads/writes mesh files with meshio and exchanges arrays with JS as raw little-endian buffers through Pyodide's in-memory filesystem.
• src/mesh/meshio.ts loads Pyodide (script tag in index.html), installs meshio via micropip, and wraps the bridge in typed async parseMeshFile/serializeMesh functions built on the internal MeshData representation (typed arrays of positions, triangle indices, optional normals/colors).
• src/mesh/formats.ts declares the supported formats and which attributes each preserves; the upload, capability table, and loss-warning UI derive from it. To add a meshio-supported format, add a descriptor there (with pyodidePackages if it needs extra prebuilt packages such as h5py) and, if it stores normals/colors in a format-specific way, teach bridge.py how to map them.