[AlexZ005]

65 gradient: the Gradient lab

A port of the ShaderGradient look (github.com/ruucm/shadergradient, MIT) inside the M2 background layer. The GLSL is ported to plain three.js; the React package is not used.

What it adds

• gradientLab shader node (Background group). It samples an offscreen target that a lazy chunk draws (src/lib/gradientLab.js, 9.8 KB, loaded only when a background uses the node). src/lib/gradientLabCore.js holds the pure rules: param schema, camera, synced clock, budget tiers, randomize, Copy as preset.
• Shapes ribbon / sphere / water with the ported noise displacement; 3 colours; ambient or procedural-environment lighting; reflection; camera azimuth/polar/distance/zoom; speed. Grain is a port of upstream's halftone dot screen on the high tier and a one-sample hash grain on lower tiers.
• Gradient lab panel in Configure Scene ▸ Background: shape, 3 colours, speed, density, strength, grain, Randomize and Copy as preset. A drag or a colour pick is one undo step. Writes go into the background document, so they replicate, save and undo like any other background edit.
• Preset index rows gain optional family + needs. The loader drops rows that need a node this build lacks, and the picker lists the family as "Gradient · Name". The presets are in packs#21.
• Determinism: the picture is a function of params + the shared clock + the target size, so two peers draw the same frame.
• Budget: VR and reduced motion show a still frame at t = 0, redrawn only on a param or size change. Phones use the low tier (coarser mesh, target ≤ 640, every 2nd frame).
• Licences: src/lib/LICENSE-shadergradient.txt (ShaderGradient + webgl-noise MIT texts) and a third-party-notices VENDORED entry.

Gates

• npm run build rc=0; check-ratchet 299/39 = baseline; check:tokens / storage / zindex clean.
• vitest: 210 files, 2625 tests pass (new tests/unit/gradientLab.test.js, 17).
• New suite gradient-lab (in battery.json): ALL PASS.
  • every preset draws, is stable on a held clock and changes with time;
  • panel: shape + framing, colour, slider, undo, Randomize, Copy as preset round trip; axe shows 0 serious/critical;
  • reduced motion: still, with exactly one redraw per edit;
  • two peers: same hash on one clock, and A's edit reaches B;
  • N6 folded/unfolded on the low tier;
  • Quest IWER probe: still sphere, 0 redraws, 38 calls / 22.5k tris + 33k lab tris.
• 65-visuals suites on this branch: background-layer 58, background-presets 81 (now also checks the Gradient family and validates the lab programs with glslangValidator), flow-background 5, fluid-layer 26, visuals-xr-iwer 19, visuals-two-peer 17.
  • visuals-two-peer 2.1 is intermittently red on the unchanged base too (A/B on ad19a01). It reads draw before B's next tick.

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