The indoor GREY flap at a top-floor connecting room. The render portal side-cull
reconstructed each doorway's "interior side" (PortalClipPlane.InsideSide) from the
cell's AABB CENTROID. For a THIN connector cell (0xF6820118, 5 render polys), the
bounding-box center falls on the WRONG side of the 0118->0116 doorway, so the eye
read as a back-portal and the forward room 0116 was culled -> the aperture showed
the fog clear color = grey.
Retail's PView::InitCell (0x005a4b70) and acdream's own PHYSICS path
(CellTransit.cs:190) both read the explicit dat PortalSide bit ((Flags&2)==0)
instead of guessing from geometry. Port the render path (GameWindow.BuildLoadedCell)
to the same bit.
Proven by a live retail cdb trace (retail draws 0116 from the 0118 root at the grey
pose; tools/cdb/issue186-connector-decider.cdb) + an offline dat diagnostic
(Issue186...PortalSide_CentroidVsDatBit_AtGreyEye): the dat bit matches the old
centroid on every portal of these cells EXCEPT the one #186 breaks, so the switch is
surgical. Full regression green (App 741 / Core 2631); the CornerFlood + Issue113
dat-loading helpers updated to the same bit confirm every real Holtburg/tower/hall
cell floods identically. Touches neither PortalSideEpsilon nor the deleted
EyeInsidePortalOpening rescue (the two DO-NOT-RETRY traps).
Live-gated: user-confirmed no grey at any camera angle; probe shows 216 root=0118
frames, 0 still grey (0118->0116 now TRV, vis=4).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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