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fix(physics): #265 landing-bounce family - retail check_contact seed + velocity-free landing commit

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Retail jump landings BOUNCE: the floor touch records both a contact plane
(grounding) AND a collision normal (collided_with_environment), and
handle_all_collisions reflects the unmodified impact velocity off it at
5% elasticity (v += -(v.n)(elasticity+1).n, DEFAULT_ELASTICITY 0.05
@0x007c6a7c). Our transition already recorded both facts; the bounce was
suppressed by the AD-25 adaptation stack in the per-tick commit: a
Velocity.Z<=0 landing gate (needed because the resolver glued ascending
movers to the ground) plus a landing Velocity.Z=0 hand-zero whose stated
purpose was making the reflect a no-op. Downhill glided instead of
bouncing, flat-ground landings had no pop, and uphill jumps flapped
between grounded/airborne against the animation machine.

Three retail mechanisms replace the stack:
- check_contact (0x0050f5b0) seeding in ResolveWithTransition: a body in
  CONTACT seeds the transition's contact only while v.contactPlane.N <=
  0.0002; moving away seeds the last-known plane alone (get_object_info
  0x00511cc0). Ascending jumps therefore run contact-free (ballistic, no
  glue) - the gate's reason-for-being is gone. The plane requirement is
  strict: Contact-without-plane is unrepresentable in retail.
- SetPositionInternal-shaped commit (0x00515330, byte-read end-to-end,
  velocity-sign-FREE): contact purely from the transition's contact
  plane, HitGround on the airborne->walkable edge, HandleAllCollisions
  with unmodified impact velocity. Whole commit gated on Ok &&
  candidateMoved (retail pc:283657 skips SetPositionInternal entirely
  when the candidate did not move) - a standing body's contact state is
  never re-derived, which is what keeps rest bit-stable (AD-41 updated).
- Byte decodes: gate override state&0x800000=Sledding, zero branch
  state&0x20000=Inelastic, reflect strictly dot<0 - our port already had
  all three correct.

Settle: real landings (>=0.25 m/s) bounce and decay geometrically;
smaller impacts are consumed by retail's unconditional small-velocity
zero, so standing never micro-bounces. Re-baselines documented in place:
landing-survival pin measures decay post-settle; LiveCompare_Tick0/376
pin the new IsOnGround=false on zero-move ticks (captured true was the
retired seed echo; tick 376's captured body carries an 11.8 m/s grounded
velocity from the deleted get_state_velocity-overwrite era); de-overlap
fixture now carries the plane real grounded bodies always have. New
pins: LandingBounceSeedingTests (ascent no-seed, rest keeps contact,
strict plane, slope 5% reversal + tangential preservation, Sledding
override).

Investigation + implementation record:
docs/research/2026-07-30-landing-bounce-family.md. Complete Release
suite: 10,031 passed / 5 skips / 0 failures.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Erik 2026-07-30 20:12:06 +02:00
parent 7fcc7db1d1
commit 2d611b2b01
10 changed files with 620 additions and 84 deletions
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47
tests/AcDream.Core.Tests/Physics/CellarUpTrajectoryReplayTests.cs
View file

@ -606,12 +606,25 @@ public class CellarUpTrajectoryReplayTests : IDisposable
/// motion). The simplest test case: replay the call and verify the
/// harness produces the same ResolveResult + bodyAfter state.
/// </summary>
/// <remarks>
/// #265 bounce rework (2026-07-30,
/// docs/research/2026-07-30-landing-bounce-family.md): the capture's
/// <c>Result.IsOnGround=true</c> on this ZERO-MOVE tick was the old
/// seed's echo — the caller's isOnGround came straight back through the
/// seeded oi flags. The retail check_contact seed (get_object_info
/// 0x00511cc0) requires a stored contact plane, and this captured body
/// has <c>cpV=false</c>, so the modern resolve reports IsOnGround=false
/// here. Production no longer consumes IsOnGround on no-move frames
/// (the candidateMoved commit gate — retail pc:283657 skips
/// SetPositionInternal entirely), so the echo is intentionally gone;
/// the comparison pins the NEW value instead.
/// </remarks>
[Fact]
public void LiveCompare_Tick0_Spawn()
{
var (engine, cache) = BuildEngineWithCellarFixtures();
var captured = LoadCapturedRecord(record => record.Tick == 0);
AssertCallMatchesCapture(engine, captured);
AssertCallMatchesCapture(engine, captured, expectStaleIsOnGroundEcho: true);
}
/// <summary>
@ -621,12 +634,24 @@ public class CellarUpTrajectoryReplayTests : IDisposable
/// the same walkable polygon + ResolveResult, the ramp geometry is
/// loaded correctly.
/// </summary>
/// <remarks>
/// #265 bounce rework (2026-07-30): same stale IsOnGround echo as
/// <see cref="LiveCompare_Tick0_Spawn"/>, with a second stale-era quirk:
/// the captured bodyBefore carries Velocity=(0.64, 11.83, 0) while
/// GROUNDED on the ramp — a value from the deleted
/// get_state_velocity-overwrite era (root motion owns walking now;
/// grounded Velocity stays ~0). dot(v, rampNormal)=+8.5 rightly fails
/// retail check_contact (0x0050f5b0: contact holds only while
/// v·n ≤ 0.0002), so the modern resolve refuses the stale contact on
/// this zero-move tick. Geometry checks (the ramp polygon) still
/// compare exactly.
/// </remarks>
[Fact]
public void LiveCompare_Tick376_OnRamp()
{
var (engine, _) = BuildEngineWithCellarFixtures();
var captured = LoadCapturedRecord(record => record.Tick == 376);
AssertCallMatchesCapture(engine, captured);
AssertCallMatchesCapture(engine, captured, expectStaleIsOnGroundEcho: true);
}
/// <summary>
@ -838,7 +863,8 @@ public class CellarUpTrajectoryReplayTests : IDisposable
/// </summary>
private static void AssertCallMatchesCapture(
PhysicsEngine engine,
ResolveCaptureRecord captured)
ResolveCaptureRecord captured,
bool expectStaleIsOnGroundEcho = false)
{
Assert.NotNull(captured.BodyBefore);
Assert.NotNull(captured.BodyAfter);
@ -867,8 +893,19 @@ public class CellarUpTrajectoryReplayTests : IDisposable
AddIfDifferent(divergences, "Result.CellId",
$"0x{captured.Result.CellId:X8}",
$"0x{harnessResult.CellId:X8}");
AddIfDifferent(divergences, "Result.IsOnGround",
captured.Result.IsOnGround, harnessResult.IsOnGround);
if (expectStaleIsOnGroundEcho)
{
// #265 bounce rework: the capture's grounded echo on this tick is
// the retired pre-check_contact seed. Pin the NEW deterministic
// value (false) so any further drift still fails loudly.
AddIfDifferent(divergences, "Result.IsOnGround(post-#265)",
false, harnessResult.IsOnGround);
}
else
{
AddIfDifferent(divergences, "Result.IsOnGround",
captured.Result.IsOnGround, harnessResult.IsOnGround);
}
AddIfDifferent(divergences, "Result.CollisionNormalValid",
captured.Result.CollisionNormalValid,
harnessResult.CollisionNormalValid);