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knife-edge port: polyClipFinish W=0 eye-plane clip + degenerate-view propagation; EyeInsidePortalOpening rescue DELETED

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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>
This commit is contained in:
Erik 2026-06-11 21:44:23 +02:00
parent 2163308032
commit 987313aa54
7 changed files with 357 additions and 130 deletions
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22
tests/AcDream.App.Tests/Rendering/PortalVisibilityBuilderTests.cs
View file

@ -131,23 +131,31 @@ public class PortalVisibilityBuilderTests
}
[Fact]
public void Build_CollapsedInteriorPortalNearEyeBeyondHalfMeter_FloodsNeighbour()
public void Build_PortalFullyBehindEye_NotFlooded_RetailEmptyClipRule()
{
// Live cellar capture (2026-06-06): 0174->0175 was traversable, but the portal projected to
// zero vertices while the chase camera was about 1.4 m from the opening plane. The flood must
// still reach the stair connector; otherwise the main-floor shell/floor disappears.
// W=0 port (2026-06-11): a portal ENTIRELY behind the eye clips to empty in retail
// polyClipFinish (every vertex w < 0 -> <3 survivors -> reject), so the flood does not
// reach its neighbour — the cell is off-screen and drawing nothing through it is correct.
//
// HISTORY: this test used to assert the OPPOSITE (rescue-era pin from a 2026-06-06 cellar
// capture, "0174->0175 must flood at 1.4 m behind the camera"). That pinned the
// EyeInsidePortalOpening rescue — the documented compensation for ProjectToClip's old
// EyePlaneW=1e-4 divergence — not retail. The rescue is deleted with the polyClipFinish
// W=0 port (docs/research/2026-06-11-polyclipfinish-w0-clip-pseudocode.md); the live
// cellar behaviors are re-verified by the dat-backed replay harnesses + the visual gate.
var cam = Cell(0x0001, new CellPortalInfo(0x0002, 0, 0, 0));
cam.PortalPolygons.Add(Quad(0f, 0f, 0.35f, 0.35f, 1.4f)); // behind eye: ProjectToNdc collapses
cam.PortalPolygons.Add(Quad(0f, 0f, 0.35f, 0.35f, 1.4f)); // entirely behind the eye
var stairs = Cell(0x0002);
var all = new Dictionary<uint, LoadedCell> { [0x0001] = cam, [0x0002] = stairs };
var vp = ViewProj();
Assert.True(PortalProjection.ProjectToNdc(cam.PortalPolygons[0], Matrix4x4.Identity, vp).Length < 3);
Assert.True(PortalProjection.ProjectToClip(cam.PortalPolygons[0], Matrix4x4.Identity, vp).Length < 3,
"a fully-behind portal must clip to empty (polyClipFinish part 1)");
var frame = PortalVisibilityBuilder.Build(
cam, Vector3.Zero, id => all.TryGetValue(id, out var c) ? c : null, vp);
Assert.Contains(0x0002u, frame.OrderedVisibleCells);
Assert.DoesNotContain(0x0002u, frame.OrderedVisibleCells);
}
[Fact]