OrcaWeb — Browser Slicer

OrcaSlicer compiled to WebAssembly. Slice STL files directly in the browser — no server, no upload, 100% private.

Live app → | Live app, multithreaded engine → | Documentation →

The Cloudflare mirror is cross-origin isolated, so it runs the real multithreaded (MT) WASM engine instead of the single-threaded build GitHub Pages is stuck with — see below.

Features

• Full OrcaSlicer engine (WASM) — same slicing quality as the desktop app
• 3D model preview + G-code layer visualiser side-by-side
• Import STL, 3MF, OBJ, and STEP files — OBJ and STEP are converted to STL by native OrcaSlicer/OCCT code compiled into the WASM engine, no extra downloads
• Import OrcaSlicer profiles (.json) from your desktop installation
• Built-in presets: Bambu Lab P1S/X1C, Prusa MK4, Ender 3, Voron 2.4

Quick start (local dev)

git clone https://github.com/Hiosdra/OrcaWeb.git
cd OrcaWeb
npm install
node scripts/download-wasm.mjs   # ~29 MB, one-time download
npm run dev

The download script fetches pre-built WASM artifacts into public/wasm/. Those files are gitignored (too large for git).

Architecture

A React UI (main thread) hands STL/3MF/OBJ/STEP files to a Web Worker running the OrcaSlicer engine compiled to WebAssembly (slicer.js + slicer.wasm, ~29 MB, includes OCCT for STEP import) and gets G-code back. There is no slicer.data — the headless flat-config slicer never reads orca/resources at runtime, so the 200 MB preload file used by older builds was eliminated entirely.

→ Full diagram and component breakdown: mkdocs-docs/architecture.md

WASM loading

In CI the WASM artifacts are downloaded from the latest immutable wasm-v2.4.2 (optionally -patchN) GitHub Release and embedded directly in the GitHub Pages deployment, so they are served from the same origin as the app — no CORS issues.

The Cloudflare Workers mirror deploy cannot host the engine itself — both slicer.wasm (~29 MB) and the multithreaded slicer-mt.wasm (~36 MB, see below) exceed Cloudflare's 25 MiB per-asset limit — so its build (npm run build:cf, see scripts/cf-build.mjs) points VITE_WASM_BASE_URL at the GitHub Pages copy, which is served with Access-Control-Allow-Origin: *.

Single-threaded vs multithreaded engine

The engine ships as two builds: a single-threaded (ST) variant (slicer.js/slicer.wasm) served everywhere, and a multithreaded (MT) variant (slicer-mt.js/slicer-mt.wasm, real oneTBB linked against Emscripten pthreads) served only where the page is cross-origin isolated — today, only the Cloudflare mirror. GitHub Pages cannot send the required Cross-Origin-Opener-Policy/Cross-Origin-Embedder-Policy headers, so it always serves ST. The worker probes for the MT engine at runtime and falls back to ST on any failure. See ADR-011 and the ST vs MT benchmark.

Self-contained WASM build (v2.4.2)

orca-wasm/ contains a clean-room Emscripten build pipeline targeting OrcaSlicer v2.4.2 (the latest stable release as of this writing), producing both the ST and MT engine variants described above.

Build the WASM module locally (Linux / macOS / WSL2 — see mkdocs-docs/wasm-build.md for full setup):

# from the repo root, not orca-wasm/
./orca-wasm/scripts/build-local-wsl.sh

Or trigger the Build WASM GitHub Actions workflow manually to publish a new wasm-v2.4.2 (optionally -patchN) release with the compiled artifacts — releases are immutable, so a rebuild never overwrites a previous one (see mkdocs-docs/wasm-build.md).

See orca-wasm/README.md for the directory layout, full C API, and build guide.

Stack

UI	React 19, TypeScript, Tailwind CSS v4
3D	Three.js (STLLoader, OrbitControls)
Bundler	Vite 8
WASM	OrcaSlicer v2.4.2 via Emscripten (own build)
Docs	Material for MkDocs
CI/CD	GitHub Actions → GitHub Pages (primary), Cloudflare Workers (mirror)

Licence

OrcaSlicer source is © 2022 SoftFever and contributors, AGPL-3.0.
OrcaWeb UI, bridge, and build infrastructure are AGPL-3.0-or-later (see LICENSE and NOTICE.md).