The user gate + bisect overturned the coincident-cell attribution: the
phantom staircase persists in the PRE-session build (bisect screenshot at
the hall wall) and is drawn by the ENTITY pipeline, untouched by any clip.
Root cause (dat-proven, DumpHallModel_PolyFlagHistogram): retail renders a
GfxObj by TRAVERSING its drawing BSP (D3DPolyRender); polygons present in
the Polygons dictionary but referenced by NO DrawingBSP node are never
drawn - they are physics/no-draw geometry. The Holtburg meeting hall
(0x010014C3) keeps its exterior stair-ramp as dictionary polys 0+1: in
the PhysicsBSP (ACE walks The Sentry on it at z 117-118; invisible-but-
walkable in retail) but orphaned from the draw tree (true at ALL degrade
levels - the LOD theory is dead, Degrades[0] IS the base model). The hill
cottage (0x01000827) carries 8 such orphans. Our extraction iterated the
dictionary -> drew the collision skeleton: the wall staircase up close,
the flying stairs over the cottage roofline from afar (orphan ramp spans
world 221-232 at z 116-124.5; visible over the cottage roof from the west).
Fix: PrepareGfxObjMeshData filters to CollectDrawingBspPolygonIds(gfxObj)
when a drawing BSP exists; models without one draw everything (unchanged).
Physics untouched (collision keeps the full physics set - retail parity).
CellStruct extraction not touched (different conventions; no orphan
evidence there yet).
Dat-backed pins: Issue113DrawingBspFilterTests (hall orphans == 0+1,
cottage orphans == 0..7). Suites: App 226 / Core 1392 + the 4
pre-existing #99-era failures / UI 420 / Net 294.
Note: the earlier shell-clip enable (927fd8f, scoped 9ce335e) remains
correct and orthogonal - it crops interior CELL geometry to apertures
outdoors; this commit removes the phantom SHELL geometry at its source.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
e46d3d9273