Ports retail ACRender::polyClipFinish (0x006b6d00, pc:702749) near-eye
semantics into PortalProjection.ProjectToClip - the fundamental fix for
the in-plane portal clip family (climb strobes, tower-top roof/floor
flap while turning; live-corroborated this session: [viewer-diff]
0xAAB30108 strobing 27x mid-climb, whole interior dropping at the top).
Pseudocode: docs/research/2026-06-11-polyclipfinish-w0-clip-pseudocode.md.
Three legs, all decomp-driven:
1. ProjectToClip clips at w >= 0 EXACTLY (was EyePlaneW=1e-4), with
retail's any-negative-w gate. Boundary intersections land at w == 0
(homogeneous directions), so a portal the eye is CROSSING yields the
correct unbounded half-region that the bounded view-region clip cuts
to the screen. A w=0 vertex cannot survive a bounded region clip
into the divide (direction fails some edge of any bounded convex
region); the measure-zero corner case is guarded non-finite->empty.
2. CellView.CanonicalKey keys ALL-COLLINEAR (zero-area) views as their
snapped segment ("L:" + extremes) instead of rejecting them - retail
PROPAGATES degenerate views (ClipPortals decomp:433651-433711
forwards any count!=0 GetClip output, no area gate anywhere), keeping
the cell behind an exactly-in-plane portal in the draw list (cells
draw whole; onward floods die naturally). Rejection dropped the
whole chain for the frame - the parked-eye knife-edge band. Finite
key space unchanged -> dedup + strict-growth convergence intact.
3. The EyeInsidePortalOpening rescue is DELETED (the T2-documented
compensation for the 1e-4 divergence) along with EyeStandingPerpDist
+ PointInPoly2D. Empty clip = no flood, period (retail's rule).
CornerFloodReplay - the gate that REFUTED the previous deletion
attempt - passes WITHOUT the rescue under the W=0 port.
Harness criterion corrected to retail's rules (it codified the rescue):
cells fully BEHIND the camera are not required (all-behind portals clip
empty in retail); monotone area holds per root regime; the two
manufactured exact-on-plane steps assert root-only (boundary root pick
is ambiguous; the in-plane portal there is ~perpendicular to the gaze =
genuinely off-screen). Build_CollapsedInteriorPortalNearEye test
inverted to pin the retail empty-clip rule (it pinned the rescue).
New pins: eye-crossing portal -> w==0 boundary verts + half-region (not
sliver); gaze-along-plane degenerate view accepted + segment-key dedup;
non-finite guard. Replay harnesses (CornerFloodReplay, Issue120,
TowerAscent, HouseExit, Issue127) all green.
Suites: App 246+1skip / Core 1430+2skip / UI 420 / Net 294.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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