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docs(physics): correct stale set_velocity claim in the 4a remote velocity comment

Browse source 
LiveEntityNetworkUpdateController.cs's TryCommitAuthoritativeVelocity
call site carried a comment claiming "MoveOrTeleport installs that
exact vector with set_velocity". The C4 route 5 byte-decode of
CPhysicsObj::MoveOrTeleport @0x00516330-0x00516438 (the immediately
preceding commit) shows this is false: the function never reads its
velocity argument's stack slot in any branch, and UnpackPositionEvent
performs no set_velocity either. The only set_velocity in the whole
accepted-Position chain zeroes the LOCAL player @0x004541B4, a
different call site entirely.

This commit only corrects the comment. The 4a call itself is left
unchanged in production, deliberately out of C4 route 5's scope — the
route governs RuntimeSetPositionOperationKind placement dispatch, not
the pre-existing remote velocity commit. #317 (docs/ISSUES.md, filed
in the previous commit) tracks the follow-up: audit the whole
accepted-Position velocity chain and either find the correct retail
source or remove the call with a divergence-register row.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Erik 2026-08-04 21:04:06 +02:00
parent 36255af0f6
commit cff52c44f4
1 changed files with 15 additions and 5 deletions
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20
src/AcDream.App/Physics/LiveEntityNetworkUpdateController.cs
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@ -2417,11 +2417,21 @@ internal sealed class LiveEntityNetworkUpdateController
update.Position.LandblockId);
}
// PositionPack::UnPack initializes an absent velocity to zero;
// MoveOrTeleport installs that exact vector with set_velocity.
// The canonical seam wakes the retained ObjectClock and body in
// one operation. Position-delta velocity below remains animation
// diagnostics and is never substituted into physics.
// 4a-family correction (2026-08-04, found and reported while
// pinning C4 route 5's D-P5 no-velocity design): the previous
// comment here claimed "MoveOrTeleport installs that exact vector
// with set_velocity". A byte-level disassembly of the PDB-paired
// binary (0x00516330-0x00516438, every branch) shows
// MoveOrTeleport never reads its velocity argument's stack slot,
// and UnpackPositionEvent performs no set_velocity either — the
// only set_velocity in the whole accepted-Position chain zeroes
// the LOCAL player (@0x004541B4). This call's actual retail
// justification is therefore NOT yet established and needs its
// own audit; what IS still true and unaffected by that finding:
// the canonical seam below wakes the retained ObjectClock and
// body in one operation, and the Position-delta velocity further
// down remains animation diagnostics, never substituted into
// physics.
if (!_liveEntities.IsCurrentPositionAuthority(
positionRecord,
acceptedPositionAuthorityVersion))