spine2d

Experimental, pure Rust runtime for Spine 4.3 (unofficial).

Important notice

• This project is unofficial and is not affiliated with Esoteric Software.
• This is a pure Rust runtime, not an FFI binding to the official spine-c / spine-cpp runtimes. Compatibility and behavioural parity are an explicit goal, but you should treat this as an experimental implementation and manage the integration risk accordingly.
• If you need “official runtime parity + support” today, use the official runtimes (or a binding to them).

Goals

• Pure Rust implementation (no C/C++ toolchain).
• Works on wasm32-unknown-unknown (web) and native targets.
• Core crate is renderer-agnostic; rendering integrations live in separate crates.
• Drive parity via oracles and upstream tests (not “approximate compatibility”).

Non-goals (for now)

• FFI bindings to the official runtimes (spine-c, spine-cpp).
• Guaranteeing perfect behavioural parity with official runtimes from day one (we are iterating toward it, with an oracle-based workflow).

Project layout

• spine2d: core runtime + parsing + renderer-agnostic render output.

• spine2d-wgpu: wgpu renderer integration built on top of spine2d.

• spine2d-web: Trunk + wgpu web demo/viewer (wasm32-unknown-unknown).

Assets / redistribution

• This repository does not ship official Spine example exports by default.
• Local dev scripts can download spine-runtimes and import example exports into assets/ for testing/demos. Make sure you comply with the Spine license terms for your usage and redistribution.

  • Import examples locally: python3 ./scripts/prepare_spine_runtimes_web_assets.py --scope tests

Optional upstream smoke tests (local data)

Some smoke tests can parse official exported example JSON files from the upstream spine-runtimes repository. These files are not committed here by default.

• Fetch + import: python3 ./scripts/fetch_spine_runtimes_examples.py --mode json --scope tests
• Import from an existing checkout: ./scripts/import_spine_runtimes_examples.zsh --mode json --scope tests
• Run tests: cargo test -p spine2d --features json,upstream-smoke
• Run tests (including .skel parsing): cargo test -p spine2d --features json,binary,upstream-smoke

Demo

wgpu demo (native)

• Minimal UV test window: cargo run -p spine2d-wgpu --example basic --features json
• Render upstream example skeletons (requires importing --mode export):
  python3 ./scripts/fetch_spine_runtimes_examples.py --mode export --scope tests
cargo run -p spine2d-wgpu --example spine_runtimes --features json -- spineboy run --speed 1.0
  • Note: the demo resets the skeleton to setup pose each frame before AnimationState::apply to avoid accumulated constraint drift.
  • Tip: the demo has an egui top bar to switch example/animation/skin and adjust speed/margin.

Web demo (wasm + Trunk)

• Install target: rustup target add wasm32-unknown-unknown
• Install Trunk: cargo install trunk --locked
• Run dev server: cd spine2d-web && trunk serve
  • Note: the viewer can load local official exports if assets/spine-runtimes/web_manifest.json exists (generated by script; not committed).
  • Note: the web demo tracks devicePixelRatio and reconfigures the surface on resize.
  • Note: the demo auto-fits the initial bounds to the viewport (camera fit is computed once from the first frame).
  • Controls: Play/Pause, Restart, Fit, Speed, Animation, Skin.

Using official example exports locally

• Prepare assets + web manifest: python3 ./scripts/prepare_spine_runtimes_web_assets.py --scope tests
• Then run: cd spine2d-web && trunk serve
  • The demo will auto-detect assets/spine-runtimes/web_manifest.json and populate the Example dropdown.
  • Optional URL params: ?example=spineboy&anim=run

License

Dual-licensed under MIT OR Apache-2.0. See LICENSE-MIT and LICENSE-APACHE.

Spine license notice

Spine is developed by Esoteric Software. This project is not affiliated with them. Using Spine runtimes and Spine data generally requires a Spine Editor license. See the official license terms: https://esotericsoftware.com/spine-editor-license