User-observed residual after f794832: creature stops to attack but
still runs slightly through the player before stopping.
Cause: at 4 m/s body velocity (RunAnimSpeed × ~1.0 speedMod) and a
60 fps tick (~16 ms), the body advances ~6.4 cm per tick. When dist
falls just below the 0.6 m DistanceToObject arrival threshold, the
arrival predicate fires and zeroes velocity — but the body has
already advanced one full tick INTO the threshold zone. That last
tick is the "running through" the user sees, especially when
combined with a player visual radius of ~0.5 m.
Fix: cap horizontal velocity in the steering branch so the body lands
EXACTLY at the arrival threshold instead of overshooting it. Pure
function in RemoteMoveToDriver (ClampApproachVelocity) so it's
testable; called from GameWindow.cs after apply_current_movement
sets RunForward velocity from the active cycle.
The clamp is a strict scale-down of the X/Y components; Z is left
to gravity / terrain handling. No-op for the flee branch — fleeing
has no overshoot risk by definition.
Tests: 1416 → 1420. Four new clamp scenarios: exact-landing (FP
tolerance), would-overshoot scale-down, already-at-threshold zeroing,
flee no-op.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
User-observed regression on commit d247aef: creature reaches melee
range and "just runs" instead of stopping to attack. Two independent
research subagents converged on the same root cause.
When ACE broadcasts a melee swing, it sends an mt=0 UpdateMotion with
ForwardCommand=AttackHigh1 (Action class, 0x10000062), motion_flags
=StickToObject, and a trailing 4-byte sticky-target guid — there is
NO preceding cmd=Ready. The swing UM IS the stop signal.
Retail's CMotionInterp::move_to_interpreted_state
(acclient_2013_pseudo_c.txt:305936-305992) bulk-copies forward_command
from the wire into InterpretedState UNCONDITIONALLY, regardless of
motion class. With forward_command=AttackHigh1, get_state_velocity
(:305172-305180) returns velocity.Y=0 because its gate is
RunForward||WalkForward — body stops moving forward. The animation
overlay (the swing) is appended on top of whatever cyclic tail is
active.
Acdream's overlay branch in GameWindow.OnLiveMotionUpdated routed
Action-class commands through PlayAction (animation overlay only) and
SKIPPED:
- ServerMoveToActive flag update — stale RunForward MoveTo state
persisted, the per-tick driver kept steering toward the prior
Origin and calling apply_current_movement.
- InterpretedState.ForwardCommand bulk-copy — even if the flag had
been cleared, the body's InterpretedState.ForwardCommand stayed
at RunForward from the prior MoveTo cycle, so
apply_current_movement kept producing forward velocity.
- MoveToPath capture — staleness-timeout band-aid masked this.
Fix: lift the _remoteDeadReckon state-update block out of the
substate-only `else` branch so it runs for both overlay and substate
paths. For non-MoveTo packets, write fullMotion + speedMod directly to
InterpretedState.ForwardCommand/ForwardSpeed (bypassing
ApplyMotionToInterpretedState, which is a heuristic helper that
silently no-ops for Action class — see MotionInterpreter.cs:941-970).
This matches retail's copy_movement_from
(acclient_2013_pseudo_c.txt:293301-293311) bulk-copy semantics.
Also corrected RemoteMoveToDriver arrival predicate to retail-faithful:
chase = dist <= DistanceToObject; flee = dist >= MinDistance. The
prior max(MinDistance, DistanceToObject) defensive port happened to
compute the right value for ACE's wire defaults but had wrong
semantics (would have failed for any retail config with MinDistance >
DistanceToObject).
Tests: 1414 → 1416. New parser test for the AttackHigh1 wire layout;
new driver tests for retail-faithful chase/flee arrival.
Defers: target-guid live resolution for type 6 packets (chase-lag
mitigation, symptom #3), StickToObject sticky-target guid trailing
field, full MoveToManager port (CheckProgressMade, pending_actions
queue, Sticky/StickTo, use_final_heading).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
User-observed regressions on commit 186a584:
1. "Monster keeps running in different directions when it should be
attacking" — chase oscillates around the player at melee range
instead of stopping. Root cause: arrival check used MinDistance
only (retail's algorithm), but ACE puts the melee threshold in
DistanceToObject (default 0.6) and leaves MinDistance at 0. So
our check was never satisfied; body kept re-targeting around the
player as each MoveTo refresh moved the destination.
Fix: arrival = dist <= max(MinDistance, DistanceToObject) + epsilon.
Honors retail when retail sets MinDistance > 0; falls through to
ACE's DistanceToObject when MinDistance is 0. Confirmed by
independent research (named retail decomp, ACE wire writers,
holtburger client) that DistanceToObject is the documented chase
threshold in ACE; retail's MinDistance is only meaningful when
server config overrides the default 0.
2. "Monster disappears, then runs in place" — entity left our
streaming view, server stopped emitting MoveTo, last destination
stayed cached. When entity re-entered view, body still steered
toward the stale point, eventually arrived (V=0), animation kept
playing → "running on the spot."
Fix: 1.5 s stale-destination timeout. ACE re-emits MoveTo at
~1 Hz during active chase; if no fresh packet for 1.5 s, the
entity has either left view, transitioned off MoveTo without us
seeing the cancel UM, or had its move cancelled server-side.
Clear destination + zero velocity so the next interpreted-motion
UM (or fresh MoveTo) drives the body cleanly.
Also confirmed (via dispatched research subagent against ACE writer
side, named retail MovementManager::PerformMovement, and holtburger):
the wire's "Origin" field IS the destination, not the start position.
My driver's interpretation was correct; the symptoms were arrival
threshold + staleness, not a misread of the wire.
Tests: 1412 → 1414 (ACE-melee arrival, retail-MinDistance arrival).
Origin-stale lag during active chase remains — server's Origin is
the target's position at packet-emit time, ~1 s behind the player.
For type 6 MoveToObject, the retail-faithful fix is target-guid
live resolution per HandleUpdateTarget @ 0x0052a7d0; deferred per
the pseudocode doc's "out of scope" list. For type 7 there's no
fix without target-velocity prediction.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Root-causing the user-reported "monsters disappearing some time +
laggy/jittery locomotion" via systematic-debugging Phase 1: our
UpdateMotion parser kept only speed/runRate/flags from a movementType
6/7 packet and discarded Origin (destination), targetGuid, and the
distance/walkRunThreshold/desiredHeading half of MovementParameters.
The integrator consequently held Body.Velocity at zero during MoveTo
("incomplete state" stabilizer 882a07c), so the body froze with legs
animating until UpdatePosition snap-teleported it — sometimes outside
the visible window (disappearing) — and constant-velocity drift along
the old heading between snaps produced jitter on every UP correction.
The 882a07c stabilizer was deliberately conservative because the state
WAS incomplete. Completing the data plumbing makes its restriction
moot: with the full MoveTo payload captured, the body solver has every
field retail's MoveToManager::HandleMoveToPosition (0x00529d80) reads.
Why: server re-emits MoveTo packets ~1 Hz with refreshed Origin while
chasing — verified in the live log (guid 0x800003B5 seq 0x01FE→0x0204
all show different cell/xyz floats). Those are heading updates we'd
been throwing away. With the full payload retained, the per-tick driver
steers body orientation toward Origin (±20° snap tolerance, π/2 rad/s
turn rate above tolerance) and lets apply_current_movement fill in
Velocity from the existing RunForward cycle — no new motion path,
just the right heading.
Scope is the minimum viable subset: target re-tracking, sticky/StickTo,
fail-distance progress detector, and sphere-cylinder distance are
server-side concerns we don't need (server's emit cadence handles all
of them). MoveToObject_Internal target-guid resolution is also skipped
— Origin is refreshed each packet, so the effective target tracks the
real entity even without a guid lookup.
Cross-references:
- docs/research/named-retail/acclient_2013_pseudo_c.txt — MoveToManager
+ MovementParameters::UnPackNet (0x0052ac50) + apply_run_to_command
(0x00527be0). 18,366 named PDB symbols make this the primary oracle.
- references/ACE/Source/ACE.Server/Physics/Animation/MoveToManager.cs
— port aid; flagged divergences (WalkRunThreshold default, set_heading
snap, inRange one-shot) called out in the new pseudocode doc.
- docs/research/2026-04-28-remote-moveto-pseudocode.md — pseudocode +
ACE divergence flags + out-of-scope list per CLAUDE.md mandatory
workflow (decompile → cross-reference → pseudocode → port).
Tests: 1404 → 1412 (parser type-7 path retention + type-6 target guid
retention; driver arrival, in-tolerance snap, beyond-tolerance step,
behind-target shortest-path turn, arrival preserves orientation,
Origin→world landblock-grid arithmetic).
Pending visual sign-off — handoff stabilizer 882a07c was the last
commit the user tested.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Erik