ISSUES #83 Phase A1. Landblock stabs (entity.Id 0xC0XXYY00+n per
LandblockLoader.cs:55) were being registered with TWO collision
shadows: the correct per-part BSP at `entity.Id*256 + partIdx`, AND a
redundant mesh-AABB-fallback cylinder at `entity.Id`. The fallback
clamped to 1.5m radius, centered at the building's mesh origin,
producing user-reported "thin air" collisions inside cottages and
within 2m of building exteriors.
The fallback was originally designed for canopy-only-BSP procedural
scenery (0x80XXYY00+n) — trees whose BSP covers the canopy but not
the trunk. Landblock stabs have full BSP coverage and don't need it.
Probe evidence (launch-thinair capture):
- 0xC0A9B479 cylinder fallback (Holtburg cottage): 104 hits in a
short capture session, all inside the cottage main room
(cell=0xA9B4013F), ~2m from the building's mesh origin.
- 0xA9B47900 BSP (the actual cottage walls): 52 legitimate hits.
Fix: one new bool _isLandblockStab + one clause in the existing
mesh-AABB-fallback gate.
Spec: docs/superpowers/specs/2026-05-21-cylinder-fallback-dedup-design.md.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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