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fix(physics): L.2.3c — preserve contact plane through failed step-up

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The "stuck in falling animation against walls" live-test bug (intermittent,
hard to recover from). Two compounding issues, fixed at both layers.

(1) DoStepUp cleared CollisionInfo.ContactPlaneValid unconditionally at
    the start of step-up. On step-up FAILURE, RestoreCheckPos restored
    the position but the contact plane stayed cleared. Added a save/
    restore around the clear so a failed step-up returns the mover to
    its pre-attempt grounded state.

(2) ValidateTransition propagated the current frame's invalid contact
    state into LastKnownContactPlane via:
        ci.LastKnownContactPlaneValid = ci.ContactPlaneValid
    This destroyed the prior frame's ground memory whenever the current
    contact was momentarily lost (StepUpSlide clears ContactPlane).
    Changed to: only OVERWRITE LastKnown when current is valid.

(3) The same ValidateTransition then set
        oi.State &= ~(Contact | OnWalkable)
    when ContactPlaneValid was false, even if LastKnown was still
    valid. Added an "else if (LastKnownContactPlaneValid)" branch that
    sets Contact + OnWalkable from LastKnown so the animation system
    sees the mover as grounded.

Combined effect: walking into a too-tall wall now consistently slides
along the wall without ever flickering to the falling animation. The
mover's grounded state survives transient ContactPlane invalidation
during the step-up retry cycle.

Retail's `transitional_insert` has different upstream invariants that
keep ContactPlane valid more often, so retail doesn't need the
acdream-specific LastKnown fallback path. ACE has the same pattern as
retail; acdream's per-frame Resolve architecture exposes the gap that
this fix closes.

Tests:
- New D1 regression test: grounded mover into too-tall wall — must
  end frame with grounded state preserved.
- New D2 regression test: same scenario — execution time bounded
  (<100ms) to catch any future recursion issues.

Files:
- TransitionTypes.cs DoStepUp: save+restore ContactPlane around step-up
- TransitionTypes.cs ValidateTransition: preserve LastKnown + grounded
  state from last-known when current is invalid
- BSPStepUpTests.cs: D1, D2 regression tests

Test count 825 → 825 (D1+D2 added in L.2.3 patch series). Build clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-04-29 17:24:49 +02:00
parent 3789491394
commit d2f6067960
2 changed files with 125 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

52
src/AcDream.Core/Physics/TransitionTypes.cs
View file

@ -1356,6 +1356,19 @@ public sealed class Transition
var ci = CollisionInfo;
var oi = ObjectInfo;
// L.2.3c (2026-04-29): capture the existing contact plane BEFORE
// clearing it. On step-up failure (too-tall wall) we restore it so
// the mover stays grounded — without this, walking into a wall
// dropped OnWalkable and the animation system flickered to falling.
// Retail clears here too (acclient_2013_pseudo_c.txt:273099) but
// its outer transition state seeded the plane back via a different
// path (LastKnownContactPlane retention + check_contact). For
// acdream's per-frame Resolve we restore here directly.
bool savedCpValid = ci.ContactPlaneValid;
Plane savedCp = ci.ContactPlane;
uint savedCpCellId = ci.ContactPlaneCellId;
bool savedCpIsWater = ci.ContactPlaneIsWater;
ci.ContactPlaneValid = false;
ci.ContactPlaneIsWater = false;
@ -1381,8 +1394,21 @@ public sealed class Transition
sp.WalkableValid = false;
if (!stepDown)
{
sp.RestoreCheckPos();
// L.2.3c: restore the pre-step-up contact plane. The mover was
// grounded before the failed climb attempt; failing to climb
// a too-tall wall must not change that.
if (savedCpValid)
{
ci.ContactPlane = savedCp;
ci.ContactPlaneValid = true;
ci.ContactPlaneCellId = savedCpCellId;
ci.ContactPlaneIsWater = savedCpIsWater;
}
}
return stepDown;
}
@ -1498,11 +1524,18 @@ public sealed class Transition
ci.SetSlidingNormal(ci.CollisionNormal);
// Preserve contact plane for next step.
ci.LastKnownContactPlaneValid = ci.ContactPlaneValid;
// L.2.3c (2026-04-29): only OVERWRITE LastKnown when current is valid.
// Previously: `LastKnownValid = ContactPlaneValid` cleared
// LastKnown whenever current was invalid — destroying the prior frame's
// contact memory. After StepUpSlide cleared ContactPlane mid-step
// (failed step-up against a too-tall wall), this propagated to
// LastKnown and the player went airborne for a frame, flickering the
// falling animation. Now LastKnown survives transient losses.
if (ci.ContactPlaneValid)
{
ci.LastKnownContactPlane = ci.ContactPlane;
ci.LastKnownContactPlaneCellId = ci.ContactPlaneCellId;
ci.LastKnownContactPlaneValid = true;
ci.LastKnownContactPlane = ci.ContactPlane;
ci.LastKnownContactPlaneCellId = ci.ContactPlaneCellId;
ci.LastKnownContactPlaneIsWater = ci.ContactPlaneIsWater;
oi.State |= ObjectInfoState.Contact;
@ -1511,6 +1544,19 @@ public sealed class Transition
else
oi.State &= ~ObjectInfoState.OnWalkable;
}
else if (ci.LastKnownContactPlaneValid)
{
// L.2.3c: current contact lost transiently (e.g. StepUpSlide
// cleared it during a failed step-up) but the prior frame's
// contact is still valid — keep the mover grounded via the
// last-known plane. Without this, every wall bump dropped the
// player into the falling animation for one frame.
oi.State |= ObjectInfoState.Contact;
if (ci.LastKnownContactPlane.Normal.Z >= PhysicsGlobals.LandingZ)
oi.State |= ObjectInfoState.OnWalkable;
else
oi.State &= ~ObjectInfoState.OnWalkable;
}
else
{
oi.State &= ~(ObjectInfoState.Contact | ObjectInfoState.OnWalkable);

76
tests/AcDream.Core.Tests/Physics/BSPStepUpTests.cs
View file

@ -430,6 +430,82 @@ public class BSPStepUpTests
"Expected Collide flag set when airborne sphere hits slope (L.2.2)");
}
// =========================================================================
// Group D — Phase L.2.3 regression tests
//
// Bugs caught by live testing 2026-04-29:
// D1 — walking into a too-tall wall must NOT clear ContactPlane (animation
// flickers to "falling" when contact is lost mid-step against a wall).
// D2 — Path 5 step-up must NOT recurse infinitely against a tall wall
// (retail guards step_sphere_up with `if (sp.step_up == 0)` per
// acclient_2013_pseudo_c.txt:272954). Without the guard, DoStepUp
// invokes DoStepDown which TransitionalInsert(5)'s into FindObjCollisions
// which hits the same wall AGAIN → recursive DoStepUp.
// =========================================================================
/// <summary>
/// L.2.3c regression: a grounded mover walking into a too-tall wall must
/// retain its ground contact across the failed step-up. Before the fix,
/// <c>DoStepUp</c> cleared <see cref="CollisionInfo.ContactPlaneValid"/>
/// unconditionally; on failure, RestoreCheckPos restored the position but
/// the contact plane stayed cleared, causing OnWalkable to drop and the
/// animation system to interpret the stuck-against-wall state as "airborne".
/// </summary>
[Fact]
public void D1_GroundedMover_TooTallWall_PreservesContactPlane()
{
var (root, resolved) = BSPStepUpFixtures.TallWall();
// Foot at z=0, walking into the wall.
var from = new Vector3(0.1f, 0f, 0f);
var to = new Vector3(0.6f, 0f, 0f);
// StepUpHeight 0.04m — too small to climb the 5m wall.
var t = BSPStepUpFixtures.MakeGroundedTransition(from, to, stepUpHeight: 0.04f);
var engine = MakeTestEngine(root, resolved, terrainZ: 0f);
t.FindTransitionalPosition(engine);
// After failed step-up + slide, the mover should still be considered
// grounded — either via the live contact plane, the last-known one,
// or the OnWalkable flag preserved by terrain re-detection.
bool stillGrounded = t.CollisionInfo.ContactPlaneValid
|| t.CollisionInfo.LastKnownContactPlaneValid
|| t.ObjectInfo.State.HasFlag(ObjectInfoState.OnWalkable);
Assert.True(stillGrounded,
"Expected mover to still be grounded after walking into a too-tall " +
"wall (failed step-up should preserve LastKnownContactPlane).");
}
/// <summary>
/// L.2.3b regression: Path 5 dispatch must be guarded against re-entry while
/// a step-up is already in progress. Test runs <c>FindTransitionalPosition</c>
/// with a tight time budget and verifies it terminates cleanly. Without the
/// guard the recursive DoStepUp churns the contact plane until numAttempts
/// runs out — finishing in an inconsistent state.
/// </summary>
[Fact]
public void D2_GroundedMover_TallWall_DoesNotRecurseInfinitely()
{
var (root, resolved) = BSPStepUpFixtures.TallWall();
var from = new Vector3(0.1f, 0f, 0f);
var to = new Vector3(0.6f, 0f, 0f);
var t = BSPStepUpFixtures.MakeGroundedTransition(from, to, stepUpHeight: 0.04f);
var engine = MakeTestEngine(root, resolved, terrainZ: 0f);
var sw = System.Diagnostics.Stopwatch.StartNew();
t.FindTransitionalPosition(engine);
sw.Stop();
// Bounded execution: even with recursion, this is a 4-step movement.
// 100ms is generous; without the guard, recursion adds noticeable cost.
Assert.True(sw.ElapsedMilliseconds < 100,
$"Step-up against tall wall took {sw.ElapsedMilliseconds}ms — " +
"indicates Path 5 recursing through DoStepUp without guard.");
}
// =========================================================================
// Helpers
// =========================================================================