# Linux 53 — profiled heightfields, slice 1

## Profile API

`WorldAssemblySurfaceProfileV1` is attached to the native SurfaceWorld recipe and stratum plan. Version 0 is the all-zero `natural` profile; it is omitted from serialized identity, preserving the existing owner world. Non-default profiles use version 1, serialize into recipe and plan JSON, and contribute to canonical hashes. Dimensions use fixed metre-derived subvoxels, and periodic phases are derived deterministically from the recipe seed and axis.

## Profiles and bounds

- **natural** retains today's noise heightfield.
- **periodicHills** uses `h = h0 + Ax cos(2πx/Lx + φx) + Ay cos(2πy/Ly + φy)`. The fixture uses `Ax=Ay=1.5 m`, `Lx=Ly=96 m`; seeded phases are Q0.32 turns `1258571205` and `82173144`. Its maximum analytic grade is 7.90° (the plan-time limit is 15°). Supported ranges follow R20: amplitudes 0.5–3 m and wavelengths 80–160 m.
- **mirroredRelief** uses `g = Ax cos(...) + Ay cos(...)`, floor `h0+g`, and ceiling `c0−λg`. The fixture uses 1.5 m amplitudes, 128 m wavelengths, and `λ=0.875`. R20 ranges are 0.5–2 m, 80–160 m, and `λ=0.75–1`. The plan checks `c0−h0−(1+λ)(Ax+Ay)` against the required clearance; the fixture requests 8 m. Its maximum grade is 5.94°.
- **flatField** sets the floor to `h0` and retains the plan's flat cap.

For each horizontal box, the cosine range checks its endpoints and all included stationary points; spans of a full period use `[-1,1]`. The two axis ranges are combined for floor and mirrored-cap bounds. Fixed-point rounding is padded outward by two subvoxels; flat-field bounds are constant. The same profile function feeds point evaluation, lattice classification, and intervals. Each profile audit checked 96 boxes against 23,328 brute-force density samples: zero interval misses and zero classifier mismatches. Each also certified 24 air and 24 solid boxes; the separate bound audit checked 265 boxes and 7,155 samples. The density sign remains negative for solid and nonnegative for air.

## Fixtures, routes, and captures

The fixtures are named `style-override-profile-periodicHills.json`, `style-override-profile-mirroredRelief.json`, and `style-override-profile-flatField.json` under `Saved/Linux/l53/fixtures/`. Each plans an inter-stratum arrival/departure passage and a 32-segment supported route. Profile proofs and passage audits pass, including interface-band and negative-thickness controls. Measured route grades are 7.904°, 5.945°, and 0° respectively; mirrored clearance is at least the requested 8 m.

Eye-height and overview captures all pass quality gates (6/6):

- Periodic hills: [eye](captures/periodicHills-eye.jpg), [overview](captures/periodicHills-overview.jpg)
- Mirrored relief: [eye](captures/mirroredRelief-eye.jpg), [overview](captures/mirroredRelief-overview.jpg)
- Flat field: [eye](captures/flatField-eye.jpg), [overview](captures/flatField-overview.jpg)

## Timings and hashes

Cold whole-view readiness, seconds:

| Compiler | Natural SurfaceWorld | periodicHills | mirroredRelief | flatField |
|---|---:|---:|---:|---:|
| Clang 19 | 1.742 | 1.336 | 1.323 | 1.330 |
| GCC | 1.911 | 1.436 | 1.409 | 1.382 |

Both compilers were freshly rebuilt from this source stamp with FP contraction off and 12 jobs. Every profile is under the 1.75 s budget; periodic hills and flat field are faster than their natural SurfaceWorld reference. Profile layout IDs are `bf3b90bc4678497e` (periodic), `bd45e0817b6338fa` (mirrored), and `dea9d3b61447f9b1` (flat).

Floating Islands and natural SurfaceWorld owner hashes each match L52 exactly: 12/12 canonical rows on Clang and GCC at W12. Profile worker hashes match at W1/W8/W12, and seeded random-camera geometry/material hashes match across Clang and GCC. Source stamp: `99389e29037f59841b46b31f16899355b718ba8def14ff73c43f8900dbb75c0b`.

## Verification and failed runs

Fast passed in 149.6 s; medium passed in 606.2 s; full passed once in 1,088.3 s. Full included 30-cell determinism and five paired baseline cost measurements. The median candidate changes were +0.87% for SurfaceWorld and +0.84% for Floating Islands.

Earlier trials exposed a lower-landing capsule-support failure and a transition-audit harness short-circuit; route radius conversion was corrected and transition checks were split. One medium attempt then failed its speed gate because passage audits contaminated `whole_view_ready` (21.666 s). The final tier measures cold views separately without audit flags and passes at the times above. No final tier gates failed.

## Orchestrator review (Claude)

Accepted as code. The stamp matches the final Clang and GCC builds (`99389e29…`); the owner hashes are identical to
L52; profile proofs show 0 misses. **All three profiles run faster than natural SW** (about 1.33 s vs 1.74 s on Clang).
**The captures don't show the profiles.** The eye views are a single soft horizon against black: the cap is never
visible, so mirrored relief can't be judged. The "periodicHills overview" frames the FI anchor spiral column from the
upper strate, which still shows its old shard and terrace artifacts, instead of the hills. The next profile round
must frame the hill field and the mirrored ceiling, for example a wide eye-level view with the cap in frame and a
high oblique overview over several periods.