Amal-David/meshy2glb

# meshy2glb Browser-based converter and viewer for [meshy.ai](https://meshy.ai)'s `.meshy` 3D model files and common 3D formats. Drop files in, preview with adjustable lighting, then export as `.glb`, `.gltf`, `.obj`, `.stl`, `.ply`, or `.usdz`. **Live:** https://amal-david.github.io/meshy2glb/ Everything runs client-side — decryption, meshopt decompression, and rendering all happen in your browser. No file ever leaves your machine. ## How it works `.meshy` files are AES-256-CTR encrypted glTF/GLB containers with meshopt-compressed vertex data. The decoder was built clean-room through reverse engineering (no meshy code or WASM in the bundle): 1. **Decrypt** — the first 8 KB of the body is AES-256-CTR encrypted with a fixed 32-byte ASCII key and a per-file nonce from the header. A 16-byte GCM auth tag follows. Everything after is plaintext. 2. **Decompress** — the decrypted GLB uses `EXT_meshopt_compression`. We run [meshoptimizer](https://github.com/zeux/meshoptimizer)'s JS decoder on every compressed bufferView to produce a standard GLB with raw vertex/index data. 3. **Render / convert** — three.js loads the model into a shared scene. The viewer provides orbit controls, adjustable lighting, wireframe mode, background presets, and auto-rotate. Exporters serialize that scene into the chosen output format. The full pipeline (decrypt → decompress → render) takes ~80 ms for a 5 MB model. ## Features - **Drag-and-drop or click to upload** — accepts `.meshy`, `.glb`, `.gltf`, `.obj`, `.stl`, `.ply`, `.dae`, `.3mf`, and `.fbx` - **Lighting controls** — exposure, environment intensity, direct light, ambient light (all real-time sliders) - **Display options** — wireframe toggle, auto-rotate, background presets (dark / grey / white / black), camera reset - **Multi-format export** — download a standard `.glb`, `.gltf`, `.obj`, `.stl`, `.ply`, or `.usdz` for Blender, Unity, Unreal, slicers, AR preview, and other model tools - **Linked asset support** — when loading `.gltf` files, select the `.bin` and texture files alongside the main file so relative asset references can resolve locally - Works on any static host — GitHub Pages, Cloudflare Pages, S3, localhost ## Run locally git clone https://github.com/Amal-David/meshy2glb cd meshy2glb ./start.sh ## Tests node --test tests/decrypt.test.mjs Tests cover format detection, AES-CTR decryption, meshopt decode integrity (zero corrupted indices), and GLB structural validation. Fixture-driven cases run on any `.meshy` files in `tests/fixtures/` or `$MESHY_FIXTURES`. ## File format (reverse-engineered) Offset Contents ──────────── ──────────────────────────────────────────────── 0..7 magic "MESHY.AI" 8..9 version (uint16 LE, observed: 1) 10..21 12-byte AES nonce 22..31 reserved 32..8224 AES-256-CTR ciphertext (always 8192 bytes) 8224..8240 16-byte AES-GCM authentication tag 8240..EOF plaintext (WebP textures + meshopt streams) Cipher: AES-256-CTR, key = `JSON{"accessors":[{"bufferView":` (literal ASCII), counter = `nonce || uint32be(2)`. The encrypted 8 KB contains the GLB header, glTF JSON, BIN chunk header, and the start of the first buffer view. Everything after the 16-byte tag is stored in the clear — textures (WebP) and meshopt- compressed vertex/index streams. Full reverse-engineering notes (including dead ends) are in [NOTES.md](./NOTES.md). ## Architecture src/ decrypt.js AES-256-CTR decryption via WebCrypto (~50 LOC) decompress.js meshopt decompression → standard GLB (~100 LOC) viewer.js three.js renderer with controls index.html UI: upload, controls panel, top bar, import/export routing tests/ decrypt.test.mjs node:test suite meshopt_decoder.module.js vendored decoder for offline tests ## Disclaimer Not affiliated with [meshy.ai](https://meshy.ai). ## License [MIT](./LICENSE)

标签：后端开发