Captures the brainstorm session 2026-05-24 evening after A6.P4 slice 1
(b49ed90) shipped without closing #99. Investigation surfaced the actual
root cause: doors register as a single 14cm × 20cm bounding-cylinder
approximation derived from Setup.Radius/Height fallback. Their real
collision-bearing geometry lives in per-part GfxObj BSPs (3 parts for
Setup 0x020019FF), including the threshold polygon spanning the doorway.
Retail-faithful design: every server-spawned entity registers N shadow
entries (one per CylSphere + one per Sphere + one per Part-with-BSP),
all sharing the same EntityId. UpdatePhysicsState propagates ETHEREAL
flips to all entries via the existing EntityId-iteration path. Unifies
the live-entity and landblock-static registration code paths under one
ShadowShapeBuilder.
Retail anchor: CObjCell::find_obj_collisions → CPhysicsObj::FindObjCollisions
→ CPartArray::FindObjCollisions → CPhysicsPart::find_obj_collisions →
CGfxObj::find_obj_collisions. One PhysicsObj per entity, parts iterated
internally for collision (acclient_2013_pseudo_c.txt:276776-275055).
Five-commit migration sequence; tests at three layers (builder unit tests,
registry behavior tests, live-capture regression pin). Approach A approved
by user 2026-05-24.
Spec stands on its own as M1.5 work; not formally assigned a phase letter
per CLAUDE.md's "don't invent phase numbers on the fly" rule.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
d71ceaba9c