CydandClaude Fable 5
3790262aad
Captures the @004abb40 decode (base head + Mover-family branch with the separating gate and mech-vs-mech ram + CulturalIcon branch with the 0x8000 stopping flag and the 0.00123f walk-through sentinel + the material tail) before implementation, so the analysis survives session boundaries. Also records two hazards BT411 fought that do NOT apply to this engine -- the compounded-reflection economy guard (our ProcessCollisionList restores velocity per contact, MOVER.CPP:1203) and the AlarmIndicator ODR split -- plus the ledger of master-perf pieces currently re-hosted in Mech::Simulate at STAGED seams, for the day mech4.cpp exists and they move home. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
86 lines
4.7 KiB
Markdown
86 lines
4.7 KiB
Markdown
# MECH4 — pre-TU reconstruction notes
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**Status: no MECH4.CPP exists yet.** The ground snap, frame rejection,
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knockdown stagger and collision economy that the binary keeps in mech4's
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master performance are currently RE-HOSTED inside `Mech::Simulate`
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([[MECH]], 5.3.98–100) at seams marked STAGED. This file carries the decode
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work for the pieces not yet written, so it survives session boundaries.
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## Mech::ProcessCollision (@004abb40) — decoded, not yet reconstructed
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The override of the engine's protected virtual (`MOVER.CPP:1354`), called
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per contact by `Mover::ProcessCollisionList`. The decomp
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(part_012.c:15206–15416) reads as the BASE function plus four additions:
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1. **The base head, verbatim**: `collisionVolume->ProcessCollision(collision,
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worldLinearVelocity, lastCollisionList, &damage->surfaceNormal,
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&penetration)`; on a miss NOTHING runs. Clamp penetration to the slice,
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ratio = pen/dt, `damage->damageAmount = StaticBounce(old, dt, r, normal,
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&elasticity, minimumBounceSpeed, &friction)` with the elasticity/friction
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locals seeded from the mover's coefficients.
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2. **The Mover-family branch** (owner = the collided solid's owner entity,
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solid+0x1c; family test FUN_0041a1a4 against the "Mover" derivation GUID
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@0x4e4518):
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* SEPARATING-CONTACT GATE: `(ourWorldVel − other->WorldVel[vtbl+0x20])
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· normal < −1e-4` (`_DAT_004ac044`) → return, no damage, no dispatch.
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* If the other's classID == **0xbb9** (mech), build a TakeDamage message
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(raw wire shape `{id, len, inflictor = DAT_0050b9ac global, zone −1,
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the Damage verbatim}`) and Dispatch it AT THE OTHER — the mech-vs-mech
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ram. Use our `Entity::TakeDamageMessage` ctor as the weapon path does.
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3. **The CulturalIcon branch** (GUID @0x4e7038):
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* `stopping = other->instanceFlags & 0x8000` (the StoppingCollisionVolume
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flag, entity+0x28).
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* Same separating gate against a ZERO other-velocity (icons are static).
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* Dispatch the crunch TakeDamage at the icon (crushable props have no
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zones → their base handler no-ops it, but the dispatch is real).
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* If NOT stopping: `damage->damageAmount = 0.00123f` (bits 0x3aa137f4) —
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the WALK-THROUGH SENTINEL. The caller (the response block in Simulate)
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must treat exactly 0.00123f as "the move stands": restore the post-snap
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saves, zero the amount, feed the gyro crunch (torque 0.4 along the
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normalized force, upward impulse 0.2 — binary @4aa81e/@4aa86c).
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4. **The material tail**: the elasticity/friction OUT values from
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StaticBounce are compared against `_DAT_004ac048`; sets
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`collisionTemporaryState` (+0x44c) to 1, or 2 when both match and the
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state was 0. The state is pushed into the `collisionState` StateIndicator
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once per frame by the response block (0→1 fires the impact sound). Needs
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the `_DAT_004ac048` constant identified before writing (likely the
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default-material coefficient — check the literal pool at 0x4ac048).
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## Two hazards the donor fought that DO NOT apply here
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* **Compounded StaticBounce reflections**: our engine's
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`Mover::ProcessCollisionList` (MOVER.CPP:1203) restores
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`worldLinearVelocity = initial_velocity` and position PER CONTACT before
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each ProcessCollision call, and averages the results. The port's
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`frameEntryWorldVelocity` economy guard has no counterpart hazard in this
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engine — do not import it.
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* **The AlarmIndicator ODR split**: a port-only problem; our tree reads
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`MovementMode()` / the alarms directly.
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## Already re-hosted in Mech::Simulate (move here when mech4.cpp exists)
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| piece | binary | landed |
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|---|---|---|
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| ground probe + snap | @4aa630–4aa6cc | 5.3.98 |
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| frame rejection + crash self-damage + knockdown | @4aa6cf–4aab0b | 5.3.99 |
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| collision economy divert + distributor | @0x4a0368 → @0049ffcc | 5.3.100 (in the damage hub, where the binary has it) |
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| status→mode limp promotion | master perf (un-decompiled) | 5.3.97, STAGED |
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| forwardCycleRate re-pick (ground/airborne) | IntegrateMotion head | partially — the ctor sets it once; the per-frame re-pick needs +0x3f4 |
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## Still to decode
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* `FUN_004a9b5c` — the master performance. Ghidra never decompiled it
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(objdump territory). Owns: the turn-in-place dispatcher (arms state 4 on
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both channels in lockstep), the status→mode promotion, likely the
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`runSpeedMax` (+0x7a0) writer, the gyro rumble timer.
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* `@004ab430` ReplicantPerformance (1432B) — the replicant-side interior.
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* `@004ab1c8` IntegrateMotion — decoded (see 5.3.95 notes) but only
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partially re-hosted: the local-velocity/orientation integration and the
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dead-reckon latency fold (+0x778/+0x77c) remain. **`+0x598` is a Point3D**
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(its replicant branch writes it with a vector subtract), so
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`motionEventName` in MECH.HPP is mistyped as CString — fix when this
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lands.
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