Phase L.4 closes the "stuck in falling animation on a steep roof" bug
the user reported on 2026-04-30 ("I jump up, I land on it. It should not
even let me land, should just slide with a falling animation"). After
this commit the body no longer sticks to a steep roof when jumping
into it — it slides along the slope while keeping the falling animation.
Two pieces:
1. BSPQuery Path 6 steep-poly slide
When an airborne sphere hits a polygon whose world normal Z is below
FloorZ (≈ 0.6642, slope > ~49°), the previous flow was:
Path 6 SetCollide → Path 4 set_walkable → ContactPlane committed →
body "lands" on the steep poly with Contact bit + falling animation.
This left the player stuck mid-slope because OnWalkable was cleared
but Contact stayed set.
The new branch detects the steep normal in Path 6 BEFORE SetCollide
is called. Instead of entering the landing path, it removes the
into-wall component of the move (project onto the steep face), sets
CollisionNormal + SlidingNormal, and returns Slid. Same shape as
Path 5's step-up fallback and CylinderCollision. The resolver retries;
the sphere is now outside the poly; FindCollisions returns OK;
ValidateTransition commits the slid position. ContactPlane is never
set, so the body stays airborne with falling animation.
2. PlayerMovementController L.3a-bounce carve-out + Inelastic stop
Re-enables the velocity-reflection bounce when the contact normal is
upward-facing but steeper than walkable (0 < N.Z < FloorZ). The base
L.3a rule suppresses bounce on landing transitions to avoid micro-
bounce on flat terrain; that suppression also stuck the player to
too-steep roofs they shouldn't land on. This carve-out re-enables
the reflection specifically for the steep upward case.
Also lands related L.2c precipice / edge-slide work that was in flight:
- TransitionTypes EdgeSlideAfterStepDownFailed: walkable-poly-steep
cliff route + steep-ContactPlane cliff route ordering, so that
CliffSlide fires when the stored walkable polygon itself is too
steep (Path 4 had previously accepted it as a "landing" via the
permissive LandingZ threshold).
- CliffSlide reference-normal selection: prefer LastWalkable, fall back
to LastKnownContactPlane only when walkable, else use world-up. This
prevents the cross(steepN, steepN) = 0 degenerate case that left the
cliff slide as a no-op when both current and last-known were steep.
- Phase 2 / step-down branch / edge-slide branch / cliff-slide
diagnostic helpers gated on ACDREAM_DUMP_EDGE_SLIDE / ACDREAM_DUMP_STEEP_ROOF.
- Two new airborne-mover regression tests in BSPStepUpTests +
PhysicsEngineTests covering wall-slide and edge tangent motion.
DEVIATION FROM RETAIL — DOCUMENTED FOR FOLLOW-UP
The Path 6 steep slide is NOT what retail does. Retail's flow on the
same hit is:
Path 6 SetCollide (no steep check) → Path 4 find_walkable returns
nothing for steep → Phase 3 reset path: restore_check_pos +
kill_velocity → return COLLIDED → validate_transition reverts CheckPos
to CurPos and forces OK.
Net retail behavior: position reverts to pre-failed-move (typically
just below the roof in the common jump-up case), velocity zeroed,
gravity rebuilds Z next frame, body falls back down naturally with
the falling animation. The "freeze" framing I used earlier was wrong;
in the typical case retail just bounces the body off and lets gravity
take over.
Strict retail behavior would match the user's intent better in the
common case AND avoid the bounce-energy-accumulation we saw with the
slide-tangent approach (V grew to ~50 m/s in continuous-contact frames).
However, retail's behavior degenerates in the edge case of an overhead
landing onto a steep slope (body would freeze mid-air above the roof).
This commit ships the slide-tangent fix as an interim "much better"
state per user verification on 2026-04-30. Follow-up work to match
retail strictly: revert Path 6 steep-slide, audit Phase 3 reset to
ensure kill_velocity (matching OBJECTINFO::kill_velocity ->
CPhysicsObj::set_velocity({0,0,0}, 0)) actually fires, and re-test.
Refs:
- acclient_2013_pseudo_c.txt:323784-323821 (Path 6 SetCollide)
- acclient_2013_pseudo_c.txt:273191-273239 (Phase 3 reset path)
- acclient_2013_pseudo_c.txt:272563-272596 (validate_transition revert)
- acclient_2013_pseudo_c.txt:274467-274475 (kill_velocity)
- acclient_2013_pseudo_c.txt:282699-282715 (handle_all_collisions bounce)
Tests: 833/833 green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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>
Port CTransition::step_up (Path 5) and SPHEREPATH::set_collide (Path 6)
from the retail decomp, turning wall-slides into proper step-up climbs
and airborne-to-roof landings.
Path 5 (grounded mover hits polygon):
- StepSphereUp calls DoStepUp which runs DoStepDown with StepUp=true
- DoStepDown now includes the retail Placement validation step
(ACE Transition.cs:731-741) — sphere must not be inside solid geometry
after finding a contact plane; this correctly blocks the tall-wall case
- FindObjCollisions now allocates a local ShadowEntry list per call to
prevent "collection modified" exceptions when DoStepUp recurses back
through TransitionalInsert → FindObjCollisions
- BSPQuery.FindCollisions passes engine through to StepSphereUp
Path 6 (airborne mover hits polygon):
- SpherePath.SetCollide: saves backup pos, records StepUpNormal, sets
WalkInterp=1 — then returns Adjusted so TransitionalInsert retries
- SpherePath.StepUpSlide: clears ContactPlane, sets SlidingNormal for
the tall-wall fallback
- TransitionalInsert Collide branch: re-tests as Placement when
ContactPlaneValid; on failure restores backup and returns Collided
Test fixes (BSPStepUpTests.cs + BSPStepUpFixtures.cs):
- Tests use foot-position convention (CurPos = foot, sphere center =
CurPos + (0,0,r)); from/to corrected from sphere-center to foot coords
- MakeTestEngine terrainZ param: 0f for grounded tests (keeps Contact
state between sub-steps), -50f for airborne/roof tests
- to.X adjusted so sub-steps land sphere inside (not exactly touching)
the wall, avoiding the EPSILON-shrink false-negative edge case
- All 12 BSPStepUp tests now GREEN; full suite 823/823
Retail refs:
CTransition::step_up — acclient_2013_pseudo_c.txt:273099 / ACE:746
CTransition::step_down — acclient_2013_pseudo_c.txt:273069 / ACE:710
SPHEREPATH::set_collide — acclient_2013_pseudo_c.txt:321594 / ACE:279
CTransition::transitional_insert Collide — pseudo_c:273193 / ACE:891
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Adds two files under tests/:
BSPStepUpFixtures.cs — synthetic PhysicsBSPNode trees for four canonical
collision shapes: low step (25 cm), too-tall wall (5 m), flat roof (3 m),
and steep slope (60deg). Pre-builds ResolvedPolygon dicts with correct
polygon_hits_sphere_precise winding (CCW relative to outward normal).
BSPStepUpTests.cs — 11 conformance tests:
A1-A6: baselines that pass before and after implementation (no-hit, geometry
fixture sanity checks).
B1-B3: Phase L.2.1 targets, currently RED (Path 5 wall-slides).
C1-C3: Phase L.2.2 targets, currently RED (Path 6 wall-slides).
Retail refs in test docstrings:
BSPTREE::find_collisions Path 5 acclient_2013_pseudo_c.txt:323849 /
ACE BSPTree.cs:192-196.
CTransition::step_up acclient_2013_pseudo_c.txt:273099-273133 /
ACE Transition.cs:746-777.
SPHEREPATH::set_collide acclient_2013_pseudo_c.txt:321594-321607 /
ACE SpherePath.cs:279-286.
CTransition::transitional_insert Collide branch
acclient_2013_pseudo_c.txt:273193-273239 / ACE Transition.cs:891-930.
Also adds PhysicsDataCache.RegisterGfxObjForTest() for test-only GfxObjPhysics
injection without real DAT content.
Test delta: 811 -> 823 (+12). 6 passing (A1-A6 + B2), 5 intentionally failing.
Pre-flight: object-translation plane D is in object-local space. Bug is dormant
for outdoor movement where terrain sets the world-space ContactPlane. Tagged TODO.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Erik