Aetheria/docs/aetheria-gravity-map.md

<!-- Prose map for campaign aetheria-gravity. Step 0b (model page and body facts) by Imagination imagination-ag2-gravity-0b, session self-2026-10-14-ag2, read at master c6519383. Target in force: aetheria-gravity:target:r2. -->
# Aetheria gravity: map

Target: `aetheria-gravity:target:r2` (rationale in `docs/aetheria-gravity-target.md`). Rulings in force: `aetheria-gravity:ruling:grid-shows-how-you-move`; from other campaigns, `aetheria-release:ruling:gravity-honest-wells-agreed`, `aetheria-fauna:ruling:ink-pillars-are-suns`, `aetheria-fauna:ruling:sim-knows-the-flow`, `aetheria-release:ruling:liquid-grid-from-sim-brushes`. Prior art: `docs/research/2026-10-14-gravity-prior-art.md`. Orbit measurements: `docs/research/2026-10-13-orbit-probe/report.md`.

## Body facts

All read at c6519383 in the detached worktree `C:\aeth-wt\ag2-docs` on 2026-10-14 unless marked. Scripts live in the Imagination scratchpad (`imagination-ag2-gravity-0b/`).

- **B1. Sim gravity today.** `Zone.GetHeight` (Zone.cs:631-658) sums the zone bowl `-PowerPulse(|p|/(2·Pack.Radius), ZoneDepthExponent)·ZoneDepth`, one PowerPulse well per `PlanetInstances` entry (radius `GravityWellRadius`, depth `GravityWellDepth`, exponent `BodyData.GravityDepthExponent`), and for every `GasGiant` (suns included) a `RadialWaves` ripple in zone time. `GetNormal` (:725-734) differences GetHeight at ±0.1; `GetForce` (:692-696) and `Ship.Update` (Ship.cs:133-135) feed the normal's xz to `GravityAcceleration` (:684-689), `S·R·(1/(1-|n|²)-1)` gated off at `|n|² <= .001`. Wells read `body.Orbit.Position`, which is float2.zero until the first `Zone.Update` (follow-up `zone-orbits-unplaced-before-first-tick`).
- **B2. The bowl and the ripples are live in code.** The operator's ruling says the zone bowl is disabled and stays so, ripples likewise. At c6519383 neither is disabled: `Settings.asset` (the only asset carrying PlanetSettings) has `ZoneDepth: 64`, `ZoneDepthExponent: 2`, `WaveDepth 0.5·m^0.3`; GetHeight applies both unconditionally; the bowl is felt only in zones with radius under about 3117 (the force gate, probe F3) and the ripples are felt around every gas giant and sun (8 to 32% of peak force, probe wave table). The drawn grid shows both: the scene `Boundary` object (PowerBrush, layer Displacement, active) is driven each frame by `ZoneRenderer` (ZoneRenderer.cs:621-622) with ZoneDepth plus ZoneBoundaryFog (0), and the `Gravity Waves` objects in `Gas Giant.prefab` and `Sun.prefab` (layer FineDisplacement, active) carry the ripple. So `flatspace-no-bowl-no-ripples` is delivered by deletion in a cut, not already true.
- **B3. The drawn grid is a second height owner.** It is not sampled from `Zone.GetHeight`. Camera `Surface Displacement` (ARPG.unity, culling layers 9 Displacement and 10 FineDisplacement) renders additive brush quads into `Assets/Resources/Fog Surface Displacement.renderTexture`, which `VolumeSampling.cs:63` publishes as the global `_NebulaSurfaceHeight`. Brushes on those layers:

  | object (where) | layer | material and shader | sim counterpart |
  |---|---|---|---|
  | Gravity Well (Planet, Gas Giant, Sun prefabs) | 9 | Gravity Well, PowerBrush, `_Power 16` fixed in the material, `_Depth` set from `GravityWellDepth`, quad scaled by `GravityWellRadius` (ZoneRenderer.cs:500-503) | the well in GetHeight, but the exponent is the material's 16, not `BodyData.GravityDepthExponent`, and the shader's envelope adds `saturate(abs(x))-.001`, `min(_Cutoff, …)` and a `smoothstep(1,.95)` rim fade the sim lacks |
  | Gravity Waves (Gas Giant, Sun) | 10 | Gravity Waves, RadialWaveBrush, `_Power 8`, `_Cutoff .5` | the ripple in GetHeight |
  | Boundary (ARPG scene) | 9 | Sector Boundary, PowerBrush, `_Power` and `_Depth` driven by ZoneRenderer | the zone bowl |
  | Waves Small / Medium / Large (ARPG scene) | 10 | Sector Waves *, SimplexBrush, depths -16.75, 7.58, 2 | none: drawn, never felt |
  | Gravity Well, Gravity Pit, Gravity Waves (Wormhole 1 prefab) | 9 | Wormhole Gravity 1 (`_Depth 54`, `_Power 4`), Wormhole Gravity (`_Depth 2000`, `_Power 64`, `_Cutoff .15`), Wormhole Waves | none: the sim has no wormhole well |
  | Gravity Well (PlanetOutpost station prefab) | 9 | Gravity Well | none found; whether this prefab is instantiated in play was not checked |

  Other cameras render the same layers into their own textures: `Patch Displacement` (layers 9, 10, 12), `Map Gravity` (9, the minimap; `MapView.cs`), `Slime Gravity Renderer` (9; `Slime.cs` binds it as `Heightmap`).
- **B4. Readers of the drawn height (GPU).** `Volumetric.cginc:121-130` (gradient of `_NebulaSurfaceHeight`, the shader's slopeFlow and surface normal; `:174` surface displacement), `Asteroid.shader:31` (displacement), `Stardust.compute:134` (`gravHeight`), `VolumeRenderCustom.shader` (property), `Slime.compute` (Heightmap), the minimap gravity materials (`ZoneRenderer.MapGravityMaterials`, `_StartDepth`/`_DepthRange` at :623-628), and the editor verifier `FlowFieldParityVerify.cs:162,261`. Follow-up `aetheria-fauna:follow_up:flow-slope-gradient-parity` already names the slopeFlow mismatch.
- **B5. Readers of the sim height and force (CPU).** Force: `Ship.Update` (Ship.cs:133-135, through GetNormal and GravityAcceleration directly, not GetForce), `Zone` floating bodies, clouds and mines (Zone.cs:411, 437, 451 via GetForce). Gradient for flow: `Zone.Flow` (:700-704). Height for placement: `Entity.cs:1849` (Position.y of non-ship entities), `Agents/States/Combat.cs:114` and `Behaviors/TurretController.cs:73` (predicted target height), `Gameplay/ItemPickup.cs:44`, `Gameplay/MineInstance.cs:59`, `ZoneRenderer.cs:545` (belt bounds) and `:581` (planet body height, minimap depth range). Ship tilt: `Ship.Update` builds Rotation from the same normal. Tests: `FloatingBodyTests.cs:187-209, 254` (pin the gate and the legacy law), `LootTests.cs:299-308`, `MineTests.cs:623-628`, `FlowFieldTests.cs` (zone with bowl as the slope source), `FireControlTests.cs:380`. Editor smoke: `FloatingItemsDrawnSmoke.cs:159`. No AI reader predicts gravity.
- **B6. Rails.** `Orbit.Period = OrbitPeriod.Evaluate(Distance)` (Zone.cs:910), with `OrbitPeriod` = 1·d^1 + 0 in Settings.asset: period is a function of distance only, never of the parent. Other readers of the same curve: `Zone.cs:599` (an orbit added at run time, phase back-solved), `Zone.cs:822` (each asteroid of a belt), `Targeting/BeltTargets.cs:63` (belt target periods). `GetOrbitPosition` (:465-500) is the closed-form rail; the root orbit has no parent and sits at `FixedPosition`. Two commented-out period writers remain in `ZoneGenerator.cs:589, 650`.
- **B7. Body well parameters.** `Planet.CalculateProperties` (Zone.cs:755-760): `BodyRadius`, `GravityWellRadius`, `GravityWellDepth` from PlanetSettings curves times per-body multipliers; `GasGiant` adds wave depth, radius, speed. The generator never writes any multiplier or `GravityDepthExponent` (no writer in ServerShared). `GasGiantData`'s wave fields reuse the JSON names `gravRadiusMul`, `depthMul` and `depthExp` (twice: `WaveDepthExponent` and `WaveSpeedMultiplier`) that `BodyData` already uses for its gravity fields; MessagePack keys differ (14-17 against 6-8), so the binary store is unambiguous and the JSON names are not. `WaveDepthExponent` is read by nothing (the sim hard-codes 8).
- **B8. Ship scale, measured headless from `GameData/Aetheria.cc`** (CultCache Python runtime, `hulls.py`, `mass.py`). Hull Drag: Longinus 0.1/s, Smoke Test Hull 0.1, Djinni 0.2, stations and turret 0. Drag is linear: `Velocity = normalize(v)·v·exp(-Drag·dt)` (Ship.cs:128-129; `CultMath.decay`). Thrust ranges: Small Drive 60-90k, Medium 100-300k, Large 200-300k, Rugged 75-250k, Burn and High-Thrust 250k-1M, Racing 200k-1.5M. `Entity.Mass` starts at hull mass and changes as items are added and removed (Entity.cs:1251, 1407). Items weigh about 40-50 per schematic cell (median over gear, weapons, cargo bays); the Longinus schematic has 66 cells, the Djinni 166. So a Longinus with one Small Drive accelerates at 24-36 u/s² empty and about 11-16 u/s² fully packed (2500 + ~3000); a Djinni 6-9 empty, about 3.4-5 packed. "Fully packed" is an estimate from cell count times median density, not a generated loadout (LoadoutGenerator was not run). Agent TopSpeed defaults to 100 (`VelocityLimit`).
- **B9. What drag means for orbits.** Holding a circular orbit at speed v costs a tangential thrust of Drag·v against drag, plus whatever radial thrust the field mismatch needs. At v = 6.3 (today's rail speed) that is 0.63 u/s² for a Longinus (2-6% of its range), 1.26 for a Djinni (14-37%); at v = 17.5 it is 1.75 (5-16%) and 3.5 (39-100%). No free orbit exists for any hull with Drag > 0; with honest wells a ship in orbit needs only the drag term, where today it also fights a radial mismatch of 17-30% of thrust (probe F2).
- **B10. Tide under superposed 1/r tails** (computed, `hill.py`, over the probe's bodies). 2D tidal radius of a parent at R from its own parent: d_H = R·sqrt(c_p/(2c_g)). Fraction of the 17,864 children of non-root parents that orbit inside 0.5·d_H: 11% if c ∝ mass, 35% for m^0.5, 59% for m^0.25, 66% for m^0.175; children of planets 1%, 10%, 30%, 38%. Speeds: if a median sun's field is 0.5 u/s² at 610 u, v_circ = 17.5 u/s around it and 12.4 around a median planet (m^0.175).
- **B11. The flow has curl.** `FlowField.Slope` (FlowField.cs:53-59) adds a swirl term, the downhill direction rotated 90 degrees, and `Global` is a noise field: neither is a gradient, so no height can show them as slopes. No ship reads `Zone.Flow`; it drives stardust and nebula (shader) and, by ruling, fauna.
- **B12. A ruling in force contradicts the target.** `aetheria-release:ruling:one-gravity-law` (Defaulted, 2026-10-07) fixes the slope-squared law and "the feel ships have today". The target replaces both. Superseded by Self on 2026-10-14.
- **B13. Removing a persisted member is compatible drift.** CultCache resolves a persisted schema against the local one slot by slot (`CultLib/src/GameCult.Caching/CultCache.cs`, `CompareSchemaShapes`, read 2026-10-14): a persisted slot the local type no longer has is listed in `IgnoredExtraSlots` with a warning, not an error. So deleting `GasGiantData` keys 14-17 (the wave fields) loads old run caches with a `content_hash_drift` warning. The shipped catalog `GameData/Aetheria.cc` holds no `aetheria.gasgiantdata` documents (B8's type listing); generated zone packs in run caches do.
- **B14. The zone bowl is exactly one well at the origin.** Bowl: `-PowerPulse(r/(2·Pack.Radius), ZoneDepthExponent)·ZoneDepth`. Well: `-PowerPulse(r/GravityWellRadius, GravityDepthExponent)·GravityWellDepth`, zero at and beyond half the radius either way (PowerPulse doubles then clamps). A `PlanetData` on a parentless orbit at `FixedPosition` zero, with `GravityRadius` constant 2·Pack.Radius, `GravityDepth` constant ZoneDepth and `GravityDepthExponent` = ZoneDepthExponent, gives the same height and force at every point. The five test fixtures that dig a bowl to get a slope (FloatingBodyTests.cs:233, LootTests.cs:289, MineTests.cs:121, FlowFieldTests.cs:49-51, FireControlTests.cs:380-381) can therefore keep every expected number. Such a fixture must also set `BodyRadius`, `GravityRadius`, `GravityDepth` and `OrbitPeriod` (null curves throw in `Planet.CalculateProperties` and the `Orbit` constructor).
- **B15. Where the drawn bowl and ripples live in Unity YAML** (scan `yamlgo.py`). `Gas Giant.prefab`: GameObject `Gravity Waves` lines 223-240, Transform 241-255, MeshFilter 256-263, MeshRenderer 264-305, parent's child entry line 34, `GasGiantObject.GravityWaves` reference line 56. `Sun.prefab`: GameObject 60-77, Transform 78-92, MeshFilter 93-100, MeshRenderer 101-142, child entry 34, reference 57. `ARPG.unity`: GameObject `Boundary` 22642-22659, Transform 22660-22674, MeshRenderer 22675-22723, MeshFilter 22724-22731, child entry 16867 (parent transform 1037490739), `ZoneRenderer.SectorBoundaryBrush` reference 16325. Neither prefab is a variant (no PrefabInstance documents).
- **B16. Unity-side code compiles only on Starfire.** The Yggdrasil verify job builds and tests `Aetheria.Shared.Tests` (ServerShared); `ZoneRenderer.cs`, `GasGiantObject.cs`, `GameSettings.cs`, scenes and prefabs are compiled and loaded only by the Unity editor. `Assets/Scripts/Editor/FloatingItemsDrawnSmoke.cs` opens `Assets/Scenes/ARPG.unity` (line 238) in batchmode and exits nonzero on failure, so it is the cheapest check that the scene still loads and the renderer compiles.
- **B17. Dead orbit writers.** `Zone.AddOrbit` (Zone.cs:269-272) and `Zone.CreateOrbit` (:594-611, the run-time orbit that back-solves its phase from `OrbitPeriod`) have no caller under Assets/Scripts or tests. Every live orbit comes from `ZonePack.Orbits` in the constructor (:157-160). `GameSettings.MinimapZoneGravityRange` (GameSettings.cs:18, Settings.asset line 23) feeds only the bowl's minimap start depth (ZoneRenderer.cs:623).
- **B18. Settings.asset is an LFS object.** At 11b2d7ad its git blob is a 3-line LFS pointer; the smudged worktree file is the YAML read in B2. `tools/context-pack.py` reads base blobs, so a spec cannot line-anchor it (cut-gravity-subtract r1 was superseded by r2 for this); edits to it are named by key, and verify jobs copy the edited file in after LFS staging.

## Model page

One row per kind this campaign touches. "Today" is c6519383; "target" is the shape under r2 with the recommended answers, marked where a question is open.

| kind | identity | lifecycle | authority (one owner per decision; forbidden writers) |
|---|---|---|---|
| **Zone potential** φ(p, t) | One per `Zone` instance, unnamed (a method, not a record). Not persisted: derived from the pack's bodies, orbits and PlanetSettings at zone time. Today it does not exist as such; GetHeight is a shaped heightfield (mass-neutral wells, probe Reading B). | Built when the zone is constructed; must be valid before the first Update (`zone-valid-before-tick`). Varies with body positions over zone time. No ripple term in flatspace (`flatspace-no-bowl-no-ripples`). Reference constant: zero at the root body's zone radius (proposal; log tails have no natural zero). | Owner: one ServerShared function (Zone's potential, likely a small pure module beside FlowField so shaders can lower it). Forbidden writers: `GravityAcceleration`'s slope-squared law and its gate, `GetNormal` as a force source, the zone bowl term, `RadialWaves`, any brush or shader that composes gravity on its own. |
| **Force** a = -∇φ | Derived, never stored. | Per query. Analytic gradient (sum of per-well closed forms), not finite differences of the height. | Owner: the potential module. Every CPU force reader (B5) calls it: ships, floating bodies, clouds, mines. Forbidden: `Ship.Update`'s private normal-to-force path; the per-second `GravityReferenceRate` restatement (dies with the old law). |
| **Body well parameters** (gravitational parameter c, softening radius R) | Derived per body from `BodyData.Mass` through PlanetSettings curves (today: `GravityDepth`, `GravityRadius`, `BodyRadius` × per-body multipliers). Names: per-body record key (`CultRecordRef<BodyData>`), injective. The JSON names of GasGiantData's wave fields collide with BodyData's (B7). | Computed once at Planet construction (`CalculateProperties`); never revised in play. Today's `GravityDepthExponent`, `GravityDepthMultiplier`, `GravityRadiusMultiplier` have no writer; the exponent dies under the target (no PowerPulse well); wave fields die in flatspace. | Owner of the curve: PlanetSettings in `Settings.asset` (open: well-strength-from-mass, softening-radius). Owner of the per-body value: `Planet` (or its successor) at construction. Forbidden writers: the brush material's `_Power 16` and `_Cutoff`, ZoneRenderer copying depth into materials, any shader constant. Cell not filled: whether per-body multipliers stay (no writer today; a pillar or authored body may want one). |
| **Pillar** (Ink zones) | The zone's central body in a sun's role (`ink-pillars-are-suns`). Cell not filled: no record names a pillar today (no `Pillar` or `Adrasteia` anywhere under Assets/Scripts at c6519383); whether it becomes a `BodyData` kind is the Ink-zone work's decision. | Built with the zone like any body. | Owner: same law as a sun (`pillars-are-suns`); its strength comes from the same curve or an authored c. Pseudospace shenanigans are not in scope. |
| **Orbit rail** (`OrbitData`: Distance, Phase, Parent, FixedPosition; runtime `Orbit`: Period, Position, PreviousPosition, Velocity) | `OrbitData` is a catalog/pack record keyed by `CultRecordKey`, parent by `CultRecordRef<OrbitData>`; root has no parent. Period is derived, not stored. | OrbitData created by ZoneGenerator only (the run-time writers `AddOrbit` and `CreateOrbit` are dead, B17, and go in cut-orbits-placed-at-build); Period computed at `Orbit` construction; Position written by `GetOrbitPosition` each Update and float2.zero before the first (follow-up). Asteroids and belt targets recompute periods from the same curve (B6). | Today: `OrbitPeriod` curve owns period and ignores the field. Target (open: rails-vs-field, recommended field-owns-rails): period derived from the parent's c, T = 2πd/sqrt(c_parent), the same derivation for the four readers in B6. Forbidden writers then: `OrbitPeriod` as an independent authority, any per-reader period formula. Position placement moves to construction (`zone-valid-before-tick`). |
| **Orbit placement** (child distances) | Generated `OrbitData.Distance` per body, authored ZoneGenerationSettings ranges. | Written once at generation; persisted in the zone pack. | Owner: ZoneGenerator. Open: moons-beyond-tidal-reach (whether the generator must keep children within their parent's tidal reach, which makes the generator read the strength curve). |
| **Zone bowl** | PlanetSettings `ZoneDepth`, `ZoneDepthExponent`, `ZoneBoundaryFog`; scene `Boundary` brush. | Live today (B2). Target: gone from flatspace gravity. | Ruled (`grid-shows-how-you-move`, `flatspace-no-bowl-no-ripples`). Forbidden: the GetHeight term, ZoneRenderer's driving of the Boundary brush on a gravity layer, FlowFieldTests' use of the bowl as a slope source (tests need a well instead). Cell not filled: whether the zone needs a non-gravitational edge (nothing asked for one). |
| **Ripples** (gas giant and sun waves) | PlanetSettings `WaveDepth`, `WaveRadius`, `WaveFrequency`, `WaveSpeed`; GasGiantData wave multipliers; Gravity Waves brush objects. | Live today (B2). Target: gone from flatspace. | Ruled. Forbidden: RadialWaves in the potential, the Gravity Waves objects on displacement layers. Pseudospace pulses (follow-up `pseudospace-flavours-campaign`) are a different kind, under the same grid invariant. |
| **Exaggeration factor** K | Not present today (height is the only quantity). Target: one number, φ = K·h. | Authored; constant in play. | Open: exaggeration-scope (recommended one global value in PlanetSettings). Owner: PlanetSettings. Forbidden: per-class or per-material depth scales, ZoneRenderer's `_StartDepth/_DepthRange` as an independent mapping of depth (it may normalise the minimap, but from h, not from brush depths). |
| **Drawn grid height** (`_NebulaSurfaceHeight` and the other displacement targets) | Render textures named in B3; global shader names. | Rendered every frame from brush quads. | Today: the brushes own it, independently of the sim (B3), which is the defect this campaign kills. Target: lowered from the sim's potential (h = φ/K), whether by an analytic shader function fed body parameters (as `FlowField` is lowered) or by brushes whose shapes are generated from the same law; the one owner is the ServerShared potential and the shader is a lowering with a parity check (as `FlowFieldParityVerify` does for flow). Forbidden: material constants (`_Power`, `_Cutoff`, `_Depth`), smoothstep rim fades, the wormhole and station gravity wells, and any brush on a gravity layer with no sim term. Open: grid-presentation-noise (what becomes of the Sector Waves noise and the liquid-grid detail). |
| **Readers that place things at the height** (B5) | Call sites. | Every frame. | Readers only. They read h = φ/K + GridOffset. No change of owner; listed so a cut finds them all. |
| **Flow** (FlowField) | PlanetSettings `Flow`; `Zone.Flow`; shader `globalFlow`/`slopeFlow`. | Zone time. | Owner: FlowField in ServerShared (`sim-knows-the-flow`). Its slope term must read the potential's gradient, not GetNormal of a separate heightfield. Open: flow-moves-ships (B11). |
| **Ship motion under gravity** | `Ship.Update`. | Per tick: drag, then position, then gravity. | Reader of the force. Hull Drag owns damping (B8, B9). Forbidden: any gravity computation local to Ship. |

Cells not filled, plainly: whether per-body well multipliers survive (no writer today, no consumer asked); what record names an Ink pillar; whether the PlanetOutpost prefab's drawn well is ever instantiated; whether the zone needs a non-gravitational edge once the bowl is gone; real generated loadout masses (B8 is a bound, not a measurement).

## Rationale

- Why the drawn grid is a lowering, not an owner: `grid-shows-how-you-move` makes the slope a promise about motion. Six brush kinds on the gravity layers have no sim term or a different envelope (B3), so today the grid shows motion that does not happen (sector noise, wormholes, rim fades) and hides motion that does (the bowl in small zones is drawn at the same depth everywhere while felt only under the gate).
- Why rails follow the field: every shipped game where ships feel gravity derives the rails from the same parameter (KSP) or simulates bodies (Outer Wilds); authored rails coexist only with no felt gravity (Elite, Starsector). See the prior-art doc, section 3.
- Why strength, softening and tide are separate questions: a·r = v² ties felt strength to body speed (field-strength); c(mass) sets both readability and how many moons a ship can follow (well-strength-from-mass, B10); R sets the peak (softening-radius). Any two can be ruled without the third.
- Why the force gate is not in the subtraction cut: deleting the gate changes forces everywhere the gate zeroed them (every core, every rim), so it is behaviour, not subtraction, and the function it lives in (`GravityAcceleration`) is deleted whole by the potential cut. Removing it first would rewrite FloatingBodyTests' gate assertions into a no-gate test of a law that dies one cut later.
- Why the bowl fixtures become a well and not a new test helper per file: B14 makes the substitution exact, so the subtraction cut changes no expected number in five behaviour tests; the potential cut then replaces the fixture's well law once, in one helper.
- Why orbits are placed at build in a sibling: it touches the zone constructor, Update and the dead run-time orbit writers (B17), none of which the subtraction cut touches, and it removes the stacked-wells-at-origin state before the potential cut needs a valid field at construction.
- A constraint for pseudospace, not solved here: a push with curl (B11) has no height, so under `grid-shows-how-you-move` it either never moves ships, or is drawn by another channel, or is restricted to its gradient part.

## Cut sequence

Mapped and admitted (2026-10-14, base 11b2d7ad): `aetheria-gravity:cut_spec:cut-gravity-subtract.r2` and its sibling `aetheria-gravity:cut_spec:cut-orbits-placed-at-build.r1`. Not yet mapped:

- **potential-owner**: one ServerShared potential (c from an authored compressed curve G·m^p, authored core-radius curve, uniform-disc core, log tail, superposition, analytic gradient, no gate, global K in PlanetSettings, reference zero at the root's zone radius); every CPU force reader (Ship, floating bodies, clouds, mines) and `Zone.Flow`'s slope term read it; GetHeight = φ/K; deletes `GravityAcceleration`, `GravityReferenceRate`, `GetNormal` as a force source, the PowerPulse well and `GravityDepthExponent`; field strength per field-strength-ruled. Waits on both admitted cuts. May split into the potential and its readers if one Hands pass cannot hold both.
- **orbits-from-field**: Orbit.Period = 2πd/sqrt(c_parent) for the orbit constructor, asteroid poses (Zone.cs:822) and BeltTargets.cs:63; `OrbitPeriod` deleted. Waits on potential-owner.
- **children-within-reach**: ZoneGenerator places children inside a fraction of the parent's tidal radius and the core radius inside the innermost child (softening-radius-ruled); tested over generated zones. Waits on orbits-from-field.
- **grid-lowering**: the renderer draws φ/K from the sim's law (analytic or generated brushes) with a parity check; deletes the Gravity Well brush constants and the wormhole gravity brushes; gravity samplers (slopeFlow, stardust, slime, minimap) read gravity only; closes `aetheria-fauna:follow_up:flow-slope-gradient-parity`. Starfire-verified. Waits on potential-owner.
- **grid-noise-presentation**: the Sector Waves noise and fine-grid detail move to non-slope presentation (grid-gravity-only-ruled). Waits on grid-lowering.
- **top-speed-field**: top speed becomes a hull field; no drag below it, drag on the excess above it; the VelocityLimit clamp (Behaviors/VelocityLimit.cs) and always-on hull drag (Ship.cs:127-129) go; AI pilots brake actively; open: drag shape above the cap, consumables as modifiers, whether loot and wreckage come to rest (aetheria-gravity:ruling:no-drag-below-top-speed, target invariant orbits-do-not-decay). Waits on potential-owner and orbits-from-field.