# Arbitrary geometry (ORN-52)

**Ship path:** load-time **bake JSON**, not in-browser STEP remesh.

Pipeline: single-body manifold hygiene → **QuadriFlow** (batch CLI when present; Instant Meshes OK interactive) → quality gates (`free=0`, non-manifold=0) → bake JSON → browser load + **density knob** → Chiron quadmem + WASM ladder (same as letters).

**Demo:** owned closed torus `meshes/torus-demo.json` (not Bunny). Suzanne is not the default.

## Reuse vs new

**Kept:** `applyBakeMesh` + quadmem + ORN-49 WASM ladder + ORN-50 camera + ORN-51 quad wire + ORN-53 P0 Details/pressure.

**Killed:** O / plus / pill presets, SVG paste/upload, live occupancy-grid remesh for this ticket.

**New:** `tools/bake_quad.py` (`TorusQuads` / `MeshQuality` / `GmshCad` STEP+STL / `QuadriFlow` hook), torus density bakes, torus button + JSON upload, this doc.

## Density

Slider 1–5 swaps **prebaked** revolution-quad files (~2–4 quads across the tube at default):

| Level | File | Quads across tube | N (default bake) |
|------:|------|------------------:|------------------:|
| 1 | `torus-demo.d1.json` | 2 | 176 |
| 2 | `torus-demo.d2.json` | 3 | 396 |
| 3 | `torus-demo.json` | 4 | 688 |
| 4 | `torus-demo.d4.json` | 6 | 1560 |
| 5 | `torus-demo.d5.json` | 8 | 2784 |

A/B/C stay on Design-PASS Gmsh bakes; the slider does not remesh letters.

## STEP / STL (CLI)

```bash
python3 tools/bake_quad.py --torus                 # owned torus density ladder (ship demo)
python3 tools/bake_quad.py --occ-torus --out /tmp/occ-torus.json
python3 tools/bake_quad.py --step part.step --out meshes/part.json
python3 tools/bake_quad.py --stl  part.stl  --out meshes/part.json
python3 tools/bake_quad.py --self-test
# QuadriFlow: put `quadriflow` on PATH (or set QUADRIFLOW). Instant Meshes OK interactive.
```

**STEP:** Gmsh OpenCASCADE import → 2-D surface mesh → Blossom recombine → QuadriFlow if present → quality gates.

**STL:** manifold hygiene; dirty/open/multi-body fail. QuadriFlow on the triangle soup is preferred; Gmsh classify+recombine is a fallback (often leftover tris).

Browser **JSON upload** (Details) loads a bake with the same schema as `meshes/A.json` / `torus-demo.json`. In-browser STEP/STL remesh is stretch (not this ship).

## Limits

- **Single-body closed shell.** Multi-body STL/STEP is rejected (euler / component count).
- **Dirty STL** (holes, non-manifold, inverted soup): hygiene fails (`free≠0` or non-manifold). Repair before bake.
- **Open shells** fail the free-edge gate.
- **Size caps:** ≤ 8000 verts, ≤ 12000 quads (see `MeshQuality`).
- **Tris** only when needed to avoid bad quads. The torus demo is all-quad (`faceTris=[]`).
- Letters remain hollow 5 cm **film** blocks. The torus is a closed tube membrane (genus 1).

Rebuild:

```bash
python3 tools/bake_quad.py --torus
python3 tools/bake_quad.py --self-test
node test/torus-bake.mjs
node test/ladder-wasm.mjs
```