#331 reported that `PhysicsEngine.ResolveWithTransition` refuses ALL uphill
motion whenever a `body:` is supplied. It does not. It refuses a step whose
sub-step offset is exactly anti-parallel to a live sliding normal — the
#137-family absorb this project already recorded as retail-faithful.
Measured on the same fixture, same gradient, same body, varying only the
heading relative to the slope gradient:
(0, -0.1, 0) cross-slope 0 -> zero movement, latched
(0.0001,-0.1, 0) cross-slope 0.0001 m -> zero movement, latched
(0.001, -0.1, 0) cross-slope 0.001 m -> climbs 0.176 m in 5 ticks
(0.01, -0.1, 0) cross-slope 0.01 m -> climbs 0.176 m in 5 ticks
The threshold is retail's own F_EPSILON small-offset abort (0.0002 m): about
0.11 degrees off the exact gradient at a 0.1 m step. `RemoteRampHarness`
builds a ramp whose gradient is exactly along Y and the original probe pushed
exactly along -Y, so it hit the measure-zero case with probability 1.
The latch itself is production-real in mechanism — a pure gravity fall under
the production RuntimeRemotePhysicsUpdater, with no fixture settle seam
involved, lands leaving Contact|OnWalkable|Sliding with slidingNormal (0,1,0)
— but every link is faithful to retail, verified in the PDB-paired binary
rather than Binary Ninja (BN typed find_transitional_position `void` and
dropped the load-bearing return value):
validate_walkable sets collision_normal from the terrain plane when
OBJECTINFO CONTACT is clear 0x0050d251 / 0x0050d261 / 0x0050d26c
validate_transition converts it unconditionally 0x0050ac19-0x0050ac30
set_sliding_normal zeroes Z AND re-normalizes 0x0050a060
SetPositionInternal persists SLIDING_TS 0x005154c2 / 0x005154e1
get_object_info re-seeds it next frame 0x00511d44 / 0x00511d4f
find_transitional_position returns
`i != 0 && state == OK` on the step-0 abort 0x0050c0ed -> 0x0050c089
ACE agrees (Transition.cs:1027, CollisionInfo.cs:58). No production code
changed; no divergence introduced, so no register row.
What lands is the coverage whose absence made this invisible — nothing in the
suite asserted that a body-bearing mover makes uphill progress on a walkable
slope, and the test that found #331 passed vacuously because the body never
moved:
RuntimeRemoteUphillProgressTests.ARemoteWithABodyClimbsAWalkableSlopeAndKeepsItsFeetOnIt
per-tick climb + surface tracking under a realistic off-gradient heading.
SAB-A1 AdjustOffset -> Vector3.Zero reddens at tick 1
SAB-A2 fixture gradient -> 0 (flat) reddens at tick 1
RuntimeRemoteUphillProgressTests.AnExactlyUpSlopeOffsetIsAbsorbedByThePersistedSlidingNormal
characterization pin for the absorb, with the retail anchors inline.
SAB-B1 delete the get_object_info sliding seed reddens (climbs to 57.7544)
SAB-A1 reddens
SAB-A2 reddens
NON-discriminating, measured and documented: making the final tick
exactly up-slope leaves it green — by then the latch is already cleared.
RemoteRampHarness gains a warning block naming the axis-alignment trap so the
next vacuous uphill assertion is caught at authoring time.
Suite re-measured from a full clean (43 bin/obj removed): 11,198 passed /
4 skipped / 0 failed, against the 11,196/4/0 baseline at 0d62a5ff — exactly
the two tests added.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
ec29a732f5