Two targeted fixes for user-reported movement bugs:
1. Wall bounce: PortalPlane.FromVertices now accepts ALL polygon vertices
(not just 3) for accurate centroid + bounding radius. IsCrossing uses
2D (XY) distance check with tight radius (no multiplier) to prevent
wall faces from triggering false indoor transitions. Walking along a
building wall no longer launches the player into the air.
2. Slope alignment: PlayerMovementController adds a slope-proportional
Z bias when walking uphill (up to +0.8 on steep slopes, grounded
only). Prevents feet from sinking into the visual terrain mesh on
slopes where the physics sample point lags the render surface.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Portal planes are infinite — IsCrossing only checked if positions
were on opposite sides of the plane, without verifying the crossing
point was near the actual portal opening. Walking 50m from a
building but crossing the same plane extension triggered false indoor
transitions, sinking the player into underground cell floors.
Fix: FromVertices now computes centroid (average of 3 vertices) and
bounding radius (max vertex distance + 2 unit padding). IsCrossing
rejects crossings where both positions are further than 2×radius
from the centroid. Only nearby crossings (within doorway range)
trigger a transition.
Also fixes jump-not-landing: the false portal transitions were
producing wrong resolvedGroundZ values during the jump arc, making
the landing check (candidateZ <= resolvedGroundZ) never true.
283 tests still green.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Adds the foundational portal-plane record for cell transition detection.
PortalPlane.FromVertices computes a normalised plane from 3 coplanar
polygon vertices via cross product + dot product; IsCrossing tests whether
a movement vector straddles the plane (strictly negative dot-product
product — exact-on-plane position returns false as specified).
4 new unit tests: normal construction, opposite-side crossing, same-side
no-crossing, start-on-plane no-crossing. All 269 tests green.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
