OrcaWeb — Browser Slicer

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

Live app, multithreaded engine → | Compatibility app (ST) → | Documentation →

The Cloudflare mirror is the primary cross-origin-isolated product deployment, so it runs the real multithreaded (MT) WASM engine. GitHub Pages remains the single-threaded (ST) compatibility deployment because it cannot send the headers required by SharedArrayBuffer — 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 one or more OrcaSlicer profiles (.json), including a machine/process set with one filament profile per material slot
• 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   # ~38 MB ST fallback for local dev
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. The worker selects the primary MT pair (slicer-mt.js + slicer-mt.wasm) on a cross-origin-isolated host and falls back to the ST pair (slicer.js + slicer.wasm) when the host or assets do not support threads. 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 highest immutable release in the wasm-v2.4.2 / wasm-v2.4.2-patchN family 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 (~38 MB) and the multithreaded slicer-mt.wasm (~37 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 multithreaded (MT) variant (slicer-mt.js/slicer-mt.wasm, real oneTBB linked against Emscripten pthreads) and a single-threaded (ST) compatibility variant (slicer.js/slicer.wasm). MT is the primary product path on the cross-origin-isolated Cloudflare mirror; GitHub Pages and other ordinary hosts use ST because they cannot send the required Cross-Origin-Opener-Policy/Cross-Origin-Embedder-Policy headers. The worker probes for MT 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 immutable wasm-v2.4.2 or wasm-v2.4.2-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).