e1beb7d31f
The suspect line is pinned at scoping: our ValidateWalkable measures the sphere's VERTICAL bottom against the plane (planted rest, perp = r*N.z) while our AdjustSphereToPlane is already a faithful tangent port — we mix the two geometries today and the planted one wins on terrain. D0 byte-pins retail's validate_walkable distance basis with an explicit STOP if it refutes the premise; D2 retests the #341 harness flip ten ways under the mechanism's stability prediction; the gate teaches the user that slightly hovering feet on steep slopes is the CORRECT retail look. Queued behind S1B and S2 — one physics slice in flight at a time. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
99 lines
5.3 KiB
Markdown
99 lines
5.3 KiB
Markdown
# S4b contract (Campaign S) — port the retail resting pair: tangent walkable rest + bare-radius push-out
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**Date:** 2026-08-07. **User decision, same day: "port the retail pair."**
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**Implementer:** one Sonnet agent, AFTER S1B and S2 have landed (one physics
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slice in flight at a time; build slots). **Review:** dual Opus. **Gate:** the
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user's eyes on a slope — feet are EXPECTED to hover slightly (authentic
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retail): ~3 cm at 30°, up to ~20 cm near the walkable limit.
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## The mechanism, settled by measurement + two decompilers (#341)
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Retail's walkable placement (`CPolygon::adjust_sphere_to_plane` @0x00538210,
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BN pseudo-C 322032 + Ghidra cross-confirm) solves
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`t = (dist ∓ r) / dot(N, stepDir)` — the sphere rests TANGENT to the slope,
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perpendicular distance = radius. Its `adjust_offset` push-out uses the BARE
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radius (AD-66's byte evidence) and is therefore structurally inert at rest.
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acdream rests PLANTED (perp = r·N.z) and its substituted r·N.z trigger is
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inert here by the same algebra. The user's live capture: bare trigger vs our
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rest would fire on 84% of grounded slope ticks (2,471/2,955), lifts 2–88 mm.
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**The pair ports together or not at all.**
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## The suspect line, pinned at scoping
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`Transition.ValidateWalkable` (TransitionTypes.cs ~3652) computes
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`lowPoint = sphereCenter − (0,0,radius)` — the sphere's VERTICAL bottom — and
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`dist = dot(lowPoint, N) + D + waterDepth`, pushing up by `dist/N.z` until
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the FEET clear the plane. Resting identity: `dot(center,N)+D = r·N.z`.
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Meanwhile our `AdjustSphereToPlane` (BSPQuery.cs:364 and its FlatBspQuery
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twin) is ALREADY a faithful tangent port of @0x00538210 — so acdream today
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mixes tangent (BSP walk solve) with planted (ValidateWalkable) and the
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planted one wins the resting height on terrain.
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## Deliverables, in order
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**D0 — byte-pin retail's `OBJECTINFO::validate_walkable` FIRST.** Grep the
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named pseudo-C; disassemble the distance basis from the PDB-paired binary if
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BN is ambiguous (the flag-idiom artifact class). The ONE question: does
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retail measure the perpendicular sphere clearance
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(`dot(center,N)+D − radius` — tangent semantics) or a vertical foot point?
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Cross-check ACE's `ObjectInfo.ValidateWalkable`. Write the pseudocode doc.
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**If retail's validate_walkable turns out to ALSO use a vertical foot point,
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STOP — the whole slice premise changes and the session lead re-decides.**
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The waterDepth term's exact placement in retail's expression must be pinned
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too (AP-10's sink-in behaviour must survive byte-for-byte).
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**D1 — port the pair, one commit:**
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1. `ValidateWalkable`'s distance basis → retail's (per D0's pin).
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2. `AdjustOffset`'s push-out → bare radius in trigger AND numerator (the
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exact diff that was withheld — its two `[Skip]`-ed conformance tests in
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`S4AdjustOffsetConformanceTests` un-skip and must pass unchanged).
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3. **AD-69 rides along:** the same block's `dist` gains retail's
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`LandDefs::get_block_offset` cell-relative correction (the plane's cell
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frame vs the mover's), per that row's citations.
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**D2 — the #341 harness anomaly retest.** With the pair in, run
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`RuntimeRemoteUphillProgressTests` TEN times (mixed single/class filters,
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one full bin/obj clean-room among them) and report every outcome. The
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mechanism predicts the absorbed-tick latch becomes STABLE at the tangent
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rest (no lift — the settle leaves perp = r, bare trigger inert). If the
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flip persists, capture per-tick positions inside the test (temporary
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prints) and report the matrix — do NOT recalibrate goldens on a flipping
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measurement.
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**D3 — conformance + regression:**
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- Exact-value tests for the new resting identity on a tilted plane
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(perp = r), the flat-ground case (unchanged: N.z=1 makes planted and
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tangent identical — this is why the suite never saw the difference), and
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the water sink-in cases (AP-10's 0.1/0.45/0.9 depths, unchanged
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behaviourally per D0's waterDepth pin).
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- The uphill no-flap guard (`Uphill_NoContactFlapAcrossTicks`) must stay
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green — the mechanism predicts it does (tangent rest + bare trigger =
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retail's own stable pair).
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- Sabotage: revert ONLY the ValidateWalkable half — the un-skipped AD-66
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exact-value tests stay green but the new resting-identity test reds AND
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a re-run of the user's capture analysis script over a synthetic planted
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rest shows the 84% fire pattern returning. Report verbatim.
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**D4 — bookkeeping (session lead does the register/ISSUES edits):** AD-66
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retires with the pair; AD-69 retires; #341 closes; the AD-65 register
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retirement gains a sibling note.
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## Scope — OUT
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The sliding/crease arm, the #331 absorb semantics (crease arm — untouched
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by this pair), any scaling change (AP-156's question is separate), indoor
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EnvCell walkable paths beyond what D0 proves shares the same
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validate_walkable, S1B's files.
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## Acceptance
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Full suite clean-room green (all bin/obj deleted first — this family has
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burned three verdicts on stale artifacts); D2's ten-run matrix reported;
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nothing committed. Absolute paths, no subagents, contradictions → STOP.
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## The gate (user, ~3 min)
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Same slope run as this morning's G1, plus: stand still on a steep slope and
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LOOK DOWN — feet slightly above the surface is CORRECT (retail's look).
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Downhill speed must remain the post-AD-65 feel. Any per-tick jitter,
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bouncing, or Falling-animation flicker on slopes = FAIL, revert the slice.
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