The Background tab fills in — facets rendered to order, eight hues in a carousel

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

DESIGN/explorations/board-backgrounds.md

@@ -1,6 +1,6 @@
 # Board background image set — exploration notes
 
-Status: **first sweep published, awaiting swatch review** (2026-08-07). Not a numbered design doc — this is working material for producing a set of bundled background images; the schema and rendering side is already settled in 03-board-ui.md § Styling ▸ Capabilities.
+Status: **sweep 1 + faceted gallery published, awaiting swatch review** (2026-08-07). Not a numbered design doc — this is working material for producing a set of bundled background images; the schema and rendering side is already settled in 03-board-ui.md § Styling ▸ Capabilities.
 
 ## What this is
 
@@ -47,6 +47,24 @@ Families (1–9 light, 10–12 dark):
 
 Rendering constraints baked into the generator (keep for sweep 2): no per-swatch SVG filters (all glow via radial gradients fading to alpha 0 — 96 filters would crawl), ≤~120 filler elements per swatch, gradient defs namespaced by swatch ID, light grounds ≥82% lightness / dark ≤20%.
 
+## Faceted gallery — user-designed originals (2026-08-07)
+
+Separate from the sweep-1 axes model: patterns designed to the user's own criteria — canvas tiled by shapes, per-shape **brightness jitter within a narrow band** doing the drawing, base brightness set by light/dark tone. Geometry is random on every render (that's part of the concept), so the gallery has a **Reroll** button; a swatch ID names the recipe, not a fixed layout.
+
+- **Artifact**: https://claude.ai/code/artifact/d27ad77f-9298-4cf1-9093-19d13a186752 (republished in place each round)
+- **Generator source**: `board-backgrounds-faceted.html` (this folder) — same seeded-PRNG + board-overlay-toggle infrastructure as sweep 1; seed = swatch ID + generation counter.
+- **facets**: grid-jittered dot scatter over an extended canvas → Bowyer–Watson Delaunay triangulation, each triangle stroked with its own fill color to kill antialiasing seams. Reference image: low-poly example on the Redesign board.
+- **bubbles**: same color logic on ~64 opaque circles, power-law radii, drawn large-first. **Set aside after round 1** ("we'll need more work on that") — round-1 recipe kept in git history of the generator file.
+
+**Round 2 (current, facets only)** — axes per the user: vertex count, color count, tone, saturation; brightness stays the narrow in-image jitter. 216 swatches = 3 color strategies × 2 tones × 4 hues × 3 saturations × 3 densities. Hue wheel narrowed to 4 representatives (amber/forest/sky/rose) to keep the cross reviewable; full wheel returns for finals.
+
+- Densities (columns): coarse 5×3 cells ≈20 triangles · medium 9×6 ≈97 · fine 14×9 ≈230.
+- Color strategies (sections): mono · duo = complement H+180° weighted 65/35 · trio = triad H±120° weighted 50/30/20, hue picked per triangle.
+- IDs `facets-<hue>-<strategy>-<density>-<tone><sat>`, e.g. `facets-sk-duo-f-l2` = sky duo fine light mid.
+- Jitters: hue ±3°, sat ±15%, brightness ±4.5 L around tone base (light 85–90, dark 17–21, rich rows get slight headroom shifts).
+
+**Shipped in-app (2026-08-07)**: the recipe is live in the board popover's Background tab (03-board-ui.md § Board popover ▸ Background tab) — Swift port in `Kanban/UI/Board/Backgrounds/`, rendered to a static `facets.png` at pick time (never a live view — the perf/sync ruling). One deliberate deviation from the gallery: the scatter grid gained a sacrificial boundary ring per density (coarse 7×5 @ margin 0.305, medium 10×7 @ 0.14, fine 15×10 @ 0.12 — interior cell size unchanged) because the gallery's fixed 0.075 margin let the ground notch the frame edge (coarse by up to 0.163 of the width — visible flat borders on the reviewed coarse swatches; medium 0.044, fine 0.004). Full-bleed coverage is now a tested invariant (`margin ≥ 0.92 × cell` both axes). Packaging question from sweep 1 is thereby answered for facets: generated on demand, not bundled.
+
 ## Next steps
 
 1. Review with overlay on; pick surviving families / specific IDs and direction tweaks ("aurora but duskier", "contours denser").