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>
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