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fix(physics): InterpolationManager review findings (L.3.1 Task 1 polish)

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Addresses code-quality review findings on commit f43f168:

C-1: Stall detection re-implemented to match retail (acclient lines
353071-353275). Tracks _progressQuantum (sum of step values per window)
+ _distanceAtWindowStart (set at window start). Primary check:
cumulative_progress < MIN_DISTANCE_TO_REACH_POSITION (0.20m absolute).
Secondary check: cumulative_progress / _progressQuantum < 0.30.
Either failing increments fail counter; blip-to-tail at >3 consecutive
fails (already correct).

C-2: Renamed StallFailCountForBlip -> StallFailCountThreshold with
clearer XML doc explaining the > vs >= semantics (blip fires when fail
count EXCEEDS the threshold, i.e. on the 4th consecutive failed window).

I-1: _haveBaselineDistance sentinel prevents first-window false
positive that was triggering spurious fails on every new motion sequence
(old code defaulted _distanceAtWindowStart to 0, making cumulative
progress always negative on frame 5).

I-3: dt <= 0 || NaN guard at AdjustOffset entry prevents NaN
propagation into PhysicsBody.Position.

I-4: Internal field renames for clarity:
  _failFrameCounter        -> _framesSinceLastStallCheck
  _failDistanceLastCheck   -> merged into _distanceAtWindowStart

I-5: Added internal Count property + InternalsVisibleTo (via
AssemblyAttribute in .csproj) so Enqueue_DropsOldestWhenAtCap20
actually verifies cap enforcement. Added assertion that head is the
second-enqueued position after overflow.

3 new tests (AdjustOffset_FirstWindow_DoesNotFalseFail,
AdjustOffset_DtZeroOrNegative_ReturnsZero,
Enqueue_AtCap20_HeadIsSecondOriginal), 16 total. All green.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
Erik 2026-05-02 19:10:23 +02:00
parent f43f168916
commit 927636ec77
3 changed files with 213 additions and 56 deletions
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5
src/AcDream.Core/AcDream.Core.csproj
View file

@ -11,6 +11,11 @@
<PackageReference Include="Chorizite.DatReaderWriter" Version="2.1.7" />
<PackageReference Include="Serilog" Version="4.0.2" />
</ItemGroup>
<ItemGroup>
<AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleToAttribute">
<_Parameter1>AcDream.Core.Tests</_Parameter1>
</AssemblyAttribute>
</ItemGroup>
<ItemGroup>
<ProjectReference Include="..\AcDream.Plugin.Abstractions\AcDream.Plugin.Abstractions.csproj" />
</ItemGroup>

144
src/AcDream.Core/Physics/InterpolationManager.cs
View file

@ -26,7 +26,7 @@ namespace AcDream.Core.Physics;
// guesses):
// MAX_INTERPOLATED_VELOCITY_MOD = 2.0
// MAX_INTERPOLATED_VELOCITY = 7.5
// MIN_DISTANCE_TO_REACH_POSITION = 0.20 (unused here — kept for reference)
// MIN_DISTANCE_TO_REACH_POSITION = 0.20 (absolute stall threshold, meters)
// DESIRED_DISTANCE = 0.05
// ─────────────────────────────────────────────────────────────────────────────
@ -68,8 +68,8 @@ public sealed class InterpolationManager
/// <summary>
/// Per-5-frame stall progress threshold (meters). Body must advance at
/// least this far in <see cref="StallCheckFrameInterval"/> frames or
/// it counts as a stall tick.
/// Retail MIN_DISTANCE_TO_REACH_POSITION (@ 0x00555D30).
/// the window counts as a stall.
/// Retail MIN_DISTANCE_TO_REACH_POSITION (@ 0x00555E42).
/// </summary>
public const float MinDistanceToReachPosition = 0.20f;
@ -83,38 +83,69 @@ public sealed class InterpolationManager
/// <summary>
/// Number of ticks between stall progress checks.
/// Retail StallCheckFrameInterval (@ 0x00555D30).
/// Retail frame_counter threshold (@ 0x00555E14).
/// </summary>
public const int StallCheckFrameInterval = 5;
/// <summary>
/// Minimum fraction of the expected advance that counts as "real
/// progress" in a stall check window. Below this fraction the
/// fail counter increments.
/// Retail StallProgressMinFraction (@ 0x00555D30).
/// Minimum fraction of cumulative progress_quantum that counts as "real
/// progress" in a stall check window. Below this fraction the window
/// counts as a stall (secondary check, applies when progress_quantum > 0).
/// Retail CREATURE_FAILED_INTERPOLATION_PERCENTAGE (@ 0x00555E73).
/// </summary>
public const float StallProgressMinFraction = 0.30f;
/// <summary>
/// Number of consecutive stall-check failures before the body is
/// blipped to the tail of the queue.
/// Retail StallFailCountForBlip (@ 0x00555D30).
/// Stall-fail counter threshold. The body is blipped to the tail of the
/// queue when <c>node_fail_counter</c> EXCEEDS this value (i.e., on the
/// 4th consecutive failed window, not the 3rd).
/// Retail: <c>node_fail_counter &gt; 3</c> (@ 0x00555F39).
/// </summary>
public const int StallFailCountForBlip = 3;
public const int StallFailCountThreshold = 3;
// ── internals ─────────────────────────────────────────────────────────────
private readonly LinkedList<InterpolationNode> _queue = new();
private int _failFrameCounter = 0;
private float _failDistanceLastCheck = 0f;
private int _failCount = 0;
/// <summary>Frames elapsed since the last 5-frame stall-check window fired.</summary>
private int _framesSinceLastStallCheck = 0;
/// <summary>
/// Cumulative sum of per-frame <c>step</c> magnitudes within the current
/// 5-frame window. Retail <c>progress_quantum</c>.
/// </summary>
private float _progressQuantum = 0f;
/// <summary>
/// Distance to the head node recorded at the START of the current
/// 5-frame window. Retail <c>original_distance</c>.
/// </summary>
private float _distanceAtWindowStart = 0f;
/// <summary>
/// True once the first valid distance sample has been taken and
/// <c>_distanceAtWindowStart</c> is populated. Guards against the
/// first-window false-positive that occurs when the field defaults to 0.
/// </summary>
private bool _haveBaselineDistance = false;
/// <summary>
/// Number of consecutive 5-frame windows that failed both the absolute
/// and ratio progress checks. Retail <c>node_fail_counter</c>.
/// Blip fires when this EXCEEDS <see cref="StallFailCountThreshold"/>.
/// </summary>
private int _failCount = 0;
// ── public API ────────────────────────────────────────────────────────────
/// <summary>True when the queue holds at least one waypoint.</summary>
public bool IsActive => _queue.Count > 0;
/// <summary>
/// Current waypoint count (visible to the test assembly for cap verification).
/// </summary>
internal int Count => _queue.Count;
/// <summary>
/// Stop interpolating: clear the queue and reset all stall counters.
/// Retail StopInterpolating / destructor cleanup.
@ -122,9 +153,11 @@ public sealed class InterpolationManager
public void Clear()
{
_queue.Clear();
_failFrameCounter = 0;
_failDistanceLastCheck = 0f;
_failCount = 0;
_framesSinceLastStallCheck = 0;
_progressQuantum = 0f;
_distanceAtWindowStart = 0f;
_haveBaselineDistance = false;
_failCount = 0;
}
/// <summary>
@ -172,8 +205,9 @@ public sealed class InterpolationManager
/// <para>
/// Returns <see cref="Vector3.Zero"/> when the queue is empty or when
/// the head node has been reached. Returns a snap delta (tail −
/// currentBodyPosition) after <see cref="StallFailCountForBlip"/>
/// consecutive stall failures, then clears the queue.
/// currentBodyPosition) after <see cref="StallFailCountThreshold"/>
/// consecutive stall failures (i.e., fail count EXCEEDS the threshold),
/// then clears the queue.
/// </para>
///
/// Retail InterpolationManager::adjust_offset (@ 0x00555D30) +
@ -189,6 +223,9 @@ public sealed class InterpolationManager
/// <returns>World-space delta to apply to the body this frame.</returns>
public Vector3 AdjustOffset(double dt, Vector3 currentBodyPosition, float maxSpeedFromMinterp)
{
// Guard: bad dt → skip entirely to prevent NaN poisoning PhysicsBody.Position.
if (dt <= 0 || double.IsNaN(dt)) return Vector3.Zero;
// Step 1: empty queue → no correction
if (_queue.First is null)
return Vector3.Zero;
@ -218,23 +255,58 @@ public sealed class InterpolationManager
// Step 7: direction × step
Vector3 delta = ((headNode.TargetPosition - currentBodyPosition) / dist) * step;
// Step 8: stall detection
_failFrameCounter++;
if (_failFrameCounter >= StallCheckFrameInterval)
{
float progress = _failDistanceLastCheck - dist;
float expected = catchUpSpeed * (float)dt * StallCheckFrameInterval;
// Step 8: stall detection (retail adjust_offset @ 0x00555E08-0x00555E92)
//
// Retail tracks two quantities across each 5-frame window:
// progress_quantum — cumulative sum of per-frame step magnitudes
// original_distance — distance to head at the START of the window
//
// At window end (frame_counter >= 5):
// cumulative_progress = original_distance - currentDist
//
// Primary check (@ 0x00555E42):
// cumulative_progress < MIN_DISTANCE_TO_REACH_POSITION (0.20 m)
// → window is a stall; increment node_fail_counter.
//
// Secondary check (@ 0x00555E73, only when progress_quantum > 0):
// cumulative_progress / progress_quantum < CREATURE_FAILED_INTERPOLATION_PERCENTAGE (0.30)
// → window is a stall; increment node_fail_counter.
//
// Both checks operate with sticky_object_id == 0 (we never have one).
// Either check failing counts the window as a stall.
//
// Blip fires when node_fail_counter > 3 (retail UseTime @ 0x00555F39).
// Window always resets (frame_counter=0, progress_quantum=0,
// original_distance=currentDist) after the check.
if (progress < StallProgressMinFraction * expected)
// Initialise window baseline on first call after Clear / new motion.
if (!_haveBaselineDistance)
{
_distanceAtWindowStart = dist;
_haveBaselineDistance = true;
}
_progressQuantum += step;
_framesSinceLastStallCheck++;
if (_framesSinceLastStallCheck >= StallCheckFrameInterval)
{
float cumulativeProgress = _distanceAtWindowStart - dist;
bool primaryFail = cumulativeProgress < MinDistanceToReachPosition;
bool secondaryFail = _progressQuantum > 0f &&
(cumulativeProgress / _progressQuantum) < StallProgressMinFraction;
if (primaryFail || secondaryFail)
{
_failCount++;
if (_failCount > StallFailCountForBlip)
// Blip-to-tail: retail UseTime (@ 0x00555F20) reads
// position_queue.tail_, copies its position to a local,
// calls CPhysicsObj::SetPositionSimple, then
// StopInterpolating. Snap target is the TAIL (the most
// recent server position), not the head.
if (_failCount > StallFailCountThreshold)
{
// Blip-to-tail: retail UseTime (@ 0x00555F20) reads
// position_queue.tail_, copies its position to a local,
// calls CPhysicsObj::SetPositionSimple, then
// StopInterpolating. Snap target is the TAIL (the most
// recent server position), not the head.
Vector3 tailPos = _queue.Last!.Value.TargetPosition;
Clear();
return tailPos - currentBodyPosition;
@ -245,8 +317,10 @@ public sealed class InterpolationManager
_failCount = 0;
}
_failDistanceLastCheck = dist;
_failFrameCounter = 0;
// Reset the 5-frame window regardless of pass/fail.
_framesSinceLastStallCheck = 0;
_progressQuantum = 0f;
_distanceAtWindowStart = dist;
}
// Step 9: return per-frame delta

120
tests/AcDream.Core.Tests/Physics/InterpolationManagerTests.cs
View file

@ -54,26 +54,50 @@ public sealed class InterpolationManagerTests
mgr.Enqueue(new Vector3(i * 1f, 0f, 0f), heading: 0f, isMovingTo: true);
}
// The next enqueue must NOT reject the entry; instead it drops the oldest.
// After the insert the queue count must still be QueueCap (not QueueCap+1).
// Sanity: queue is at cap before the 21st enqueue.
Assert.Equal(InterpolationManager.QueueCap, mgr.Count);
// The 21st enqueue must drop the oldest (x=0) and keep the count at cap.
mgr.Enqueue(new Vector3(100f, 0f, 0f), heading: 0f, isMovingTo: true);
// We can't query Count directly (it's internal), but IsActive must remain
// true, and we verify the cap behaviour indirectly by confirming the call
// did not throw (the queue is bounded) and the manager is still active.
Assert.True(mgr.IsActive);
// Count must still be QueueCap — not QueueCap+1.
Assert.Equal(InterpolationManager.QueueCap, mgr.Count);
// Drive the body toward the head until the queue empties, counting pops.
// If the cap was honoured (count stayed at QueueCap after the 21st push)
// the head should be position x=1 (the 2nd element) rather than x=0 (the
// original first, which was dropped).
//
// We verify this by snapping the body right onto the FarTarget step and
// counting how many AdjustOffset calls return zero after reaching a node.
//
// Simpler: just confirm the queue can be cleared completely.
mgr.Clear();
Assert.False(mgr.IsActive);
// The head (oldest surviving node) must now be x=1 (the second-original
// position), not x=0 (which was dropped). Verify by driving the body
// to exactly x=1 — AdjustOffset must pop that node (distance < DesiredDistance)
// and return zero, confirming x=1 is the head.
var bodyAtSecondOriginal = new Vector3(1f, 0f, 0f);
var result = mgr.AdjustOffset(
dt: 0.016,
currentBodyPosition: bodyAtSecondOriginal,
maxSpeedFromMinterp: 10f);
// Reached head (dist ≈ 0) → zero delta + node popped.
Assert.Equal(Vector3.Zero, result);
// One node was consumed; count must now be QueueCap - 1.
Assert.Equal(InterpolationManager.QueueCap - 1, mgr.Count);
}
[Fact]
public void Enqueue_AtCap20_HeadIsSecondOriginal()
{
// Complementary test for the cap overflow: after 21 enqueues the
// second-enqueued position (x=1) must be at the head, not x=0.
var mgr = Make();
for (int i = 0; i < InterpolationManager.QueueCap; i++)
{
mgr.Enqueue(new Vector3(i * 1f, 0f, 0f), heading: 0f, isMovingTo: true);
}
mgr.Enqueue(new Vector3(100f, 0f, 0f), heading: 0f, isMovingTo: true);
// Place the body far away from x=0 but RIGHT on x=1. If x=0 were the
// head the result would be non-zero (body is 1 m away from x=0).
// If x=1 is the head the distance is 0 → pop → zero return.
var bodyAtX1 = new Vector3(1f, 0f, 0f);
var delta = mgr.AdjustOffset(dt: 0.016, currentBodyPosition: bodyAtX1, maxSpeedFromMinterp: 10f);
Assert.Equal(Vector3.Zero, delta);
}
[Fact]
@ -218,7 +242,7 @@ public sealed class InterpolationManagerTests
{
// Body stays at origin every frame — zero real progress.
// After 5 frames the stall check fires and _failCount increments (to 1).
// Queue must still be alive (blip only at > StallFailCountForBlip = 3).
// Queue must still be alive (blip only at > StallFailCountThreshold = 3).
var mgr = Make();
var target = new Vector3(50f, 0f, 0f);
mgr.Enqueue(target, heading: 0f, isMovingTo: true);
@ -228,7 +252,7 @@ public sealed class InterpolationManagerTests
mgr.AdjustOffset(dt: 0.016, currentBodyPosition: BodyOrigin, maxSpeedFromMinterp: 4f);
}
// 1 fail < StallFailCountForBlip (3), so queue is still active.
// 1 fail < StallFailCountThreshold (3), so queue is still active.
Assert.True(mgr.IsActive);
}
@ -264,7 +288,7 @@ public sealed class InterpolationManagerTests
[Fact]
public void AdjustOffset_3FailsTriggersBlipToTail()
{
// Need > StallFailCountForBlip (3) failures.
// Need > StallFailCountThreshold (3) failures.
// Each failure requires one stall-check window (5 frames of no progress).
// So we need 4 × 5 = 20 frames with the body frozen at origin.
//
@ -279,7 +303,7 @@ public sealed class InterpolationManagerTests
// 4 stall-check windows × 5 frames each = 20 frames, body never moves.
Vector3? blipDelta = null;
const int totalFrames = (InterpolationManager.StallFailCountForBlip + 1)
const int totalFrames = (InterpolationManager.StallFailCountThreshold + 1)
* InterpolationManager.StallCheckFrameInterval;
for (int i = 0; i < totalFrames; i++)
@ -303,4 +327,58 @@ public sealed class InterpolationManagerTests
// Queue must be cleared after blip (retail StopInterpolating).
Assert.False(mgr.IsActive);
}
// =========================================================================
// New tests: I-1 first-window false-positive guard, I-3 dt guard, I-5 cap
// =========================================================================
[Fact]
public void AdjustOffset_FirstWindow_DoesNotFalseFail()
{
// Before the fix, _distanceAtWindowStart defaulted to 0, so on the
// first 5-frame window cumulative_progress = 0 - dist = -dist < 0.20
// → every new motion sequence triggered a spurious stall fail.
//
// After the fix, the baseline is seeded from the first call, so
// cumulative_progress = dist(frame0) - dist(frame4) which for a body
// that hasn't moved yet is ≈ 0. That is still < MIN (0.20), but the
// _failCount starts at 0 and must be > 3 (not == 1) to blip. The key
// assertion is that after exactly ONE stall window the queue is still
// alive (fail count == 1, blip requires > 3).
var mgr = Make();
mgr.Enqueue(new Vector3(50f, 0f, 0f), heading: 0f, isMovingTo: true);
// Run exactly one check-window (5 frames) with the body frozen.
for (int i = 0; i < InterpolationManager.StallCheckFrameInterval; i++)
{
mgr.AdjustOffset(dt: 0.016, currentBodyPosition: BodyOrigin, maxSpeedFromMinterp: 4f);
}
// One window fail → _failCount == 1, far below StallFailCountThreshold (3).
// Queue must still be active; no spurious blip on first window.
Assert.True(mgr.IsActive,
"First stall window must NOT trigger a blip (would require > 3 consecutive failures).");
}
[Fact]
public void AdjustOffset_DtZeroOrNegative_ReturnsZero()
{
var mgr = Make();
mgr.Enqueue(FarTarget, heading: 0f, isMovingTo: true);
// dt == 0 → guard fires, return zero, no side-effects.
var deltaZero = mgr.AdjustOffset(dt: 0.0, currentBodyPosition: BodyOrigin, maxSpeedFromMinterp: 4f);
Assert.Equal(Vector3.Zero, deltaZero);
// dt < 0 → guard fires, return zero.
var deltaNeg = mgr.AdjustOffset(dt: -1.0, currentBodyPosition: BodyOrigin, maxSpeedFromMinterp: 4f);
Assert.Equal(Vector3.Zero, deltaNeg);
// dt = NaN → guard fires, return zero.
var deltaNaN = mgr.AdjustOffset(dt: double.NaN, currentBodyPosition: BodyOrigin, maxSpeedFromMinterp: 4f);
Assert.Equal(Vector3.Zero, deltaNaN);
// Queue must still be intact (guards did not consume or corrupt state).
Assert.True(mgr.IsActive);
}
}