flutter3d_webgl 0.4.0

A WebGL2 backend for flutter3d: the second implementation of flutter3d_hardware, and the one that tells us whether the HAL is a seam or a description of Impeller.

flutter3d_webgl

flutter3d_hardware over WebGL2, for a build that runs in a browser.

final device = await openWebGl(width: 1280, height: 720);
final renderer = Renderer.create(device: device);

Its value is not only that it runs on the web. It is the first thing that could say whether the graphics interface is a seam or a description of Impeller, because a fake backend can only confirm that a call exists, never that it is implementable. test/engine_parity_test.dart draws the same scene through this backend and through the hardware one and compares the two pictures.

Shaders

There is no compiled bundle here — a browser compiles GLSL itself, so a "bundle" is a map from the engine's entry point names to source text. It is generated from flutter3d_shaders:

dart run tool/generate_shaders.dart

CI regenerates it and diffs, because the file it produces was once a year out of date and the browser was drawing a different sky from Impeller with nothing able to see it.

Where it stands against Impeller

All thirty-two golden scenes, between 0.01% and 0.6% of pixels differing by more than 8 per channel — the silhouette's worth of disagreement two rasterisers always have. test/cross_backend_test.dart holds each scene to its own measured budget, so a scene that starts drifting is named rather than absorbed into one tolerance covering everything.

Six scenes were once in whole percents, and every one of them was this backend drawing something else — an empty frame from a uniform block WebGL2 refuses to leave unbound, a mesh reading one texture coordinate for a whole quad because an attribute divisor was left set, a bloom chain composited upside down, a cube shadow atlas addressed by the wrong row. ARCHITECTURE.md §13 keeps what each turned out to be.

Running the tests

Five of the six test files are @TestOn('browser'):

flutter test --platform chrome

---

Part of flutter3d, an independent implementation of a 3D engine for Flutter — not a fork or a binding of another engine, and not affiliated with the Flutter team. Three switchable rendering backends: Impeller via Flutter GPU, WebGL2, and a software rasteriser. glTF, OBJ and .f3d loading, six lighting models, shadows, bloom, skinning, animation, BVH culling and picking; a deterministic fixed-step game layer with collision, navigation, positional audio, and gamepad and touch input. Three example games — shooter, platformer, racing — each built on its genre package: flutter3d_game_shooter, flutter3d_game_platformer, flutter3d_game_racing. A new game starts from apps/flutter3d_template_app. Documentation: https://flutter3d.pleion.dev.