Extends the trajectory replay harness with a programmatic mini-stair
piece, reconstructed from the live capture's polydump data
(docs/research/2026-05-21-a6-captures/scen4_cottage_cellar_polydump).
NEW finding: the cellar ramp polygon is NOT in cellStruct.PhysicsPolygons.
It lives in a separate GfxObjPhysics (the cellar's stair-piece static
building) registered via ShadowObjectRegistry, queried via
FindObjCollisions → engine.DataCache.GetGfxObj. CellDumpSerializer is
CORRECT — it captures the cell's physics polygons accurately. The
ramp polygon comes from a different data source entirely.
The polydump probe at BSPQuery.AdjustSphereToPlane:402 reports
"cell=0xA9B40147 polyId=0x0008 sides=Landblock" because the SPHERE
is in that cell at hit time — but the polygon's actual source is the
building's GfxObj. Inside the cellar fixture, polyId=0x0008 happens
to be a wall (Normal=(1,0,0)); inside the building's GfxObj, polyId
=0x0008 is the ramp (Normal=(0,-0.719,0.695) local). Same ID, different
collection.
The new RegisterStairRampGfxObj() in the harness constructs the
building's ramp polygon in WORLD coordinates (translated from
local building frame + 180° yaw), wraps it in a minimal one-leaf
PhysicsBSPTree, registers via cache.RegisterGfxObjForTest, and
attaches a ShadowEntry with cellScope=CellarId so the shadow is only
queried when the sphere is in the cellar cell (matches retail's
per-cell shadow scoping for interior statics — Issue #91 family).
Verified: world plane n=(0,0.719,0.695), d=-69.5035 (matches live
cdb capture exactly to 4 sig figs). Ramp foot at world Y=8.745,
Z=90.955; ramp top at world Y=5.845, Z=93.955. 3.0 m vertical rise.
NEW blocker discovered: the sphere goes airborne at tick 1 (same
issue documented in the prior commit's Finding #2). Sphere FLOATS
at Z=91.43 over the cellar floor, never contacts the synthetic
ramp. The synthetic stair registration mechanics are validated (the
GfxObj is in the cache, the ShadowEntry is in the registry, the
BSP tree is well-formed) — but trajectory replay still blocked on
the seeded-grounded-state bug. Next session needs to diagnose
WHY the engine reports "hit=yes n=(0,0,1) walkable=False" on tick 1
for a sphere correctly seeded as grounded on the cellar floor.
Test baseline maintained: 1167 + 4 (harness) = 1171 + 8 pre-existing
failures.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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