acdream/tests/AcDream.App.Tests/Rendering/PortalProjectionTests.cs
Erik 987313aa54 knife-edge port: polyClipFinish W=0 eye-plane clip + degenerate-view propagation; EyeInsidePortalOpening rescue DELETED
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>
2026-06-11 21:44:23 +02:00

458 lines
23 KiB
C#

using System;
using System.Numerics;
using AcDream.App.Rendering;
using Xunit;
namespace AcDream.App.Tests.Rendering;
public class PortalProjectionTests
{
// A simple GL-style perspective looking down -Z, camera at origin.
private static Matrix4x4 ViewProj()
{
var view = Matrix4x4.CreateLookAt(Vector3.Zero, new Vector3(0, 0, -1), Vector3.UnitY);
var proj = Matrix4x4.CreatePerspectiveFieldOfView(1.0f, 1.0f, 0.1f, 1000f);
return view * proj;
}
[Fact]
public void Project_QuadInFront_ProducesNdcInsideViewport()
{
// A 2x2 quad at z=-5 (in front), cell-local == world (identity transform).
var poly = new[]
{
new Vector3(-1, -1, -5), new Vector3(1, -1, -5), new Vector3(1, 1, -5), new Vector3(-1, 1, -5),
};
var r = PortalProjection.ProjectToNdc(poly, Matrix4x4.Identity, ViewProj());
Assert.True(r.Length >= 3);
foreach (var v in r)
{
Assert.InRange(v.X, -1.001f, 1.001f);
Assert.InRange(v.Y, -1.001f, 1.001f);
}
}
[Fact]
public void Project_QuadFullyBehind_ReturnsEmpty()
{
var poly = new[]
{
new Vector3(-1, -1, 5), new Vector3(1, -1, 5), new Vector3(1, 1, 5), new Vector3(-1, 1, 5),
};
var r = PortalProjection.ProjectToNdc(poly, Matrix4x4.Identity, ViewProj());
Assert.True(r.Length < 3);
}
[Fact]
public void Project_QuadStraddlingCamera_ClipsWithoutInversion()
{
// Spans from behind (z=+2) to in front (z=-5). Must clip to the in-front part,
// never produce a wildly out-of-range inverted vertex.
var poly = new[]
{
new Vector3(-1, -1, 2), new Vector3(1, -1, -5), new Vector3(1, 1, -5), new Vector3(-1, 1, 2),
};
var r = PortalProjection.ProjectToNdc(poly, Matrix4x4.Identity, ViewProj());
Assert.True(r.Length >= 3);
foreach (var v in r)
{
// A corner a few cm in front of the eye and ~1 m to the side genuinely
// projects large (~±37 NDC) but finite. ±50 still catches the ±7852
// perspective-inversion blow-up the old w-clip produced.
Assert.InRange(v.X, -50f, 50f); // bounded — no inversion blow-up
Assert.InRange(v.Y, -50f, 50f);
}
}
[Fact]
public void Project_QuadStraddlingCamera_DownstreamIntersectionIsValidOnScreen()
{
var poly = new[]
{
new Vector3(-1, -1, 2), new Vector3(1, -1, -5), new Vector3(1, 1, -5), new Vector3(-1, 1, 2),
};
var projected = PortalProjection.ProjectToNdc(poly, Matrix4x4.Identity, ViewProj());
Assert.True(projected.Length >= 3);
// The viewport region (NDC [-1,1]^2), same as CellView.FullScreen()'s single polygon.
var viewport = CellView.FullScreen().Polygons[0].Vertices;
var onScreen = ScreenPolygonClip.Intersect(projected, viewport);
Assert.True(onScreen.Length >= 3); // a non-empty visible region survives
foreach (var v in onScreen)
{
Assert.InRange(v.X, -1.001f, 1.001f);
Assert.InRange(v.Y, -1.001f, 1.001f);
}
}
[Fact]
public void Project_QuadStraddlingCamera_NdcStaysWithinScreen()
{
// R1 void-flap fix (2026-06-05): the eye-plane-only clip (w>MinW) let small-w verts
// explode under the perspective divide (~±37 NDC). Those off-screen NDC then corrupted
// the downstream 2D ScreenPolygonClip, which at glancing/close angles collapsed to EMPTY
// -> OutsideView empty -> terrain Skip -> the bluish "void" at the cottage doorway.
// Clipping the 4 frustum SIDE planes in clip space (homogeneous, before the divide)
// bounds every projected vertex to the screen [-1,1] by construction. RED before the fix.
var poly = new[]
{
new Vector3(-1, -1, 2), new Vector3(1, -1, -5), new Vector3(1, 1, -5), new Vector3(-1, 1, 2),
};
var r = PortalProjection.ProjectToNdc(poly, Matrix4x4.Identity, ViewProj());
Assert.True(r.Length >= 3);
foreach (var v in r)
{
Assert.InRange(v.X, -1.001f, 1.001f); // bounded to the screen — no off-screen explosion
Assert.InRange(v.Y, -1.001f, 1.001f);
}
}
[Fact]
public void Project_CloseDoorway_NdcStaysWithinScreen_AndCoversScreen()
{
// The probe-confirmed void frame (2026-06-05): the chase eye is ~0.28 m from the front-door
// EXIT portal — well inside RetailChaseCamera's 1.0 m near plane — and looking through it.
// The door subtends the whole screen, but the old clip produced NDC like (10.2,-67.4) and
// ScreenPolygonClip reduced it to clip=0 (the void). After the homogeneous side-plane clip
// the NDC stays on-screen AND the door still covers the viewport (non-empty), not the void.
var view = Matrix4x4.CreateLookAt(Vector3.Zero, new Vector3(0, 0, -1), Vector3.UnitY);
var proj = Matrix4x4.CreatePerspectiveFieldOfView(MathF.PI / 3f, 16f / 9f, 1.0f, 5000f); // RetailChaseCamera
var viewProj = view * proj;
// A 2 m x 2 m doorway 0.28 m in front of the eye, facing it.
var doorway = new[]
{
new Vector3(-1f, -1f, -0.28f), new Vector3(1f, -1f, -0.28f),
new Vector3(1f, 1f, -0.28f), new Vector3(-1f, 1f, -0.28f),
};
var projected = PortalProjection.ProjectToNdc(doorway, Matrix4x4.Identity, viewProj);
Assert.True(projected.Length >= 3);
foreach (var v in projected)
{
Assert.InRange(v.X, -1.001f, 1.001f);
Assert.InRange(v.Y, -1.001f, 1.001f);
}
var viewport = CellView.FullScreen().Polygons[0].Vertices;
var onScreen = ScreenPolygonClip.Intersect(projected, viewport);
Assert.True(onScreen.Length >= 3, "a doorway the eye looks through must cover the screen, not collapse to the void");
}
[Fact]
public void Project_PortalEyeIsAlmostTouching_StaysVisibleOnScreen()
{
// Regression (2026-06-03 doorway "void"): the chase camera orbits to ~0.1 m from a
// doorway portal. With RetailChaseCamera's 1.0 m near plane and the old w+z>=0 GL
// near-clip — which, for a D3D CreatePerspectiveFieldOfView matrix, discards everything
// within ~0.5 m of the eye — the whole doorway was clipped to empty, so the room behind
// it was culled and rendered as a dark void (camera-orientation dependent; rotating away
// fixed it). The eye-clip must be near-INDEPENDENT: a portal you're standing in must
// still project (covering the screen) so the cell behind stays visible.
var view = Matrix4x4.CreateLookAt(Vector3.Zero, new Vector3(0, 0, -1), Vector3.UnitY);
var proj = Matrix4x4.CreatePerspectiveFieldOfView(MathF.PI / 3f, 16f / 9f, 1.0f, 5000f); // RetailChaseCamera
var viewProj = view * proj;
// A 2 m x 2 m doorway 0.1 m in front of the eye, facing it.
var doorway = new[]
{
new Vector3(-1f, -1f, -0.1f), new Vector3(1f, -1f, -0.1f),
new Vector3(1f, 1f, -0.1f), new Vector3(-1f, 1f, -0.1f),
};
var projected = PortalProjection.ProjectToNdc(doorway, Matrix4x4.Identity, viewProj);
Assert.True(projected.Length >= 3,
"a doorway 0.1 m from the eye must still project (was clipped to empty -> void)");
var viewport = CellView.FullScreen().Polygons[0].Vertices;
var onScreen = ScreenPolygonClip.Intersect(projected, viewport);
Assert.True(onScreen.Length >= 3,
"the cell behind a doorway you're standing in must stay visible (the void bug)");
}
// ---------------------------------------------------------------------------
// Faithful homogeneous (w-space) portal clip — port of retail PView::GetClip +
// PrimD3DRender::xformStart + ACRender::polyClipFinish (decomp 432344 / 424310 /
// 702749). The early divide + fixed side-plane clamp (ProjectToNdc) collapsed
// grazing/near portals to zero-area edge slivers (-> the flap) and near doorways
// to empty (-> the void/fallback). The faithful pipeline keeps homogeneous clip
// coords (ProjectToClip — eye-plane clip only, no divide) and runs Sutherland-
// Hodgman against the view region with w-aware edge tests, dividing the survivors
// only after they are bounded to the region (ClipToRegion). 2026-06-06.
// ---------------------------------------------------------------------------
private static Vector2[] FullScreenCcw() => new[]
{
new Vector2(-1f, -1f), new Vector2(1f, -1f), new Vector2(1f, 1f), new Vector2(-1f, 1f),
};
[Fact]
public void ProjectToClip_QuadInFront_KeepsVertsWithPositiveW()
{
var poly = new[]
{
new Vector3(-1, -1, -5), new Vector3(1, -1, -5), new Vector3(1, 1, -5), new Vector3(-1, 1, -5),
};
var clip = PortalProjection.ProjectToClip(poly, Matrix4x4.Identity, ViewProj());
Assert.True(clip.Length >= 3);
foreach (var v in clip)
Assert.True(v.W > 0f, $"an in-front portal vertex must keep w>0 (homogeneous), got w={v.W}");
}
[Fact]
public void ProjectToClip_QuadFullyBehind_ReturnsEmpty()
{
var poly = new[]
{
new Vector3(-1, -1, 5), new Vector3(1, -1, 5), new Vector3(1, 1, 5), new Vector3(-1, 1, 5),
};
Assert.True(PortalProjection.ProjectToClip(poly, Matrix4x4.Identity, ViewProj()).Length < 3);
}
[Fact]
public void ClipToRegion_OnScreenQuad_ReturnsBoundedNdc()
{
// A small 2x2 quad at z=-5 is fully on-screen; clipping against the full screen
// returns it bounded to [-1,1].
var poly = new[]
{
new Vector3(-1, -1, -5), new Vector3(1, -1, -5), new Vector3(1, 1, -5), new Vector3(-1, 1, -5),
};
var clip = PortalProjection.ProjectToClip(poly, Matrix4x4.Identity, ViewProj());
var ndc = PortalProjection.ClipToRegion(clip, FullScreenCcw());
Assert.True(ndc.Length >= 3);
foreach (var v in ndc) { Assert.InRange(v.X, -1.001f, 1.001f); Assert.InRange(v.Y, -1.001f, 1.001f); }
}
[Fact]
public void ClipToRegion_FullyOffScreen_ReturnsEmpty_NotSliver()
{
// The flap's root: a portal entirely off one screen edge. The old early-divide +
// side-plane clamp collapsed it to a zero-area sliver pinned to x=1.0 (proj=3) that
// propagated a degenerate region one hop and then died; the faithful clip returns
// EMPTY so the flood stops cleanly. Quad at z=-5, x in [3,5] -> ndc x ~[1.1,1.8], off right.
var poly = new[]
{
new Vector3(3, -1, -5), new Vector3(5, -1, -5), new Vector3(5, 1, -5), new Vector3(3, 1, -5),
};
var clip = PortalProjection.ProjectToClip(poly, Matrix4x4.Identity, ViewProj());
var ndc = PortalProjection.ClipToRegion(clip, FullScreenCcw());
Assert.True(ndc.Length < 3, $"fully off-screen portal must clip to empty, got {ndc.Length} verts (sliver)");
}
[Fact]
public void ClipToRegion_PartlyOffScreen_ClipsToBoundedNonEmpty()
{
// A quad straddling the right edge -> clipped to the on-screen part, bounded, non-empty.
var poly = new[]
{
new Vector3(0, -1, -5), new Vector3(4, -1, -5), new Vector3(4, 1, -5), new Vector3(0, 1, -5),
};
var clip = PortalProjection.ProjectToClip(poly, Matrix4x4.Identity, ViewProj());
var ndc = PortalProjection.ClipToRegion(clip, FullScreenCcw());
Assert.True(ndc.Length >= 3, "a partly-on-screen portal must produce a non-empty clipped region");
foreach (var v in ndc) { Assert.InRange(v.X, -1.001f, 1.001f); Assert.InRange(v.Y, -1.001f, 1.001f); }
}
[Fact]
public void ClipToRegion_DoorwayEyeLooksThrough_CoversScreen_WithoutFallback()
{
// The void frame: chase eye 0.28 m from a 2x2 m doorway, looking through it. The doorway
// subtends the whole screen. The faithful clip keeps the homogeneous verts (no early-divide
// blow-up) and clips to the screen quad -> covers the screen (non-empty). This is what makes
// the EyeInsidePortalOpening *fallback* unnecessary for an in-front doorway.
var view = Matrix4x4.CreateLookAt(Vector3.Zero, new Vector3(0, 0, -1), Vector3.UnitY);
var proj = Matrix4x4.CreatePerspectiveFieldOfView(MathF.PI / 3f, 16f / 9f, 1.0f, 5000f);
var viewProj = view * proj;
var doorway = new[]
{
new Vector3(-1f, -1f, -0.28f), new Vector3(1f, -1f, -0.28f),
new Vector3(1f, 1f, -0.28f), new Vector3(-1f, 1f, -0.28f),
};
var clip = PortalProjection.ProjectToClip(doorway, Matrix4x4.Identity, viewProj);
var ndc = PortalProjection.ClipToRegion(clip, FullScreenCcw());
Assert.True(ndc.Length >= 3, "a doorway the eye looks through must cover the screen, not collapse to the void");
foreach (var v in ndc) { Assert.InRange(v.X, -1.001f, 1.001f); Assert.InRange(v.Y, -1.001f, 1.001f); }
}
[Fact]
public void ClipToRegion_StraddlingEye_OnScreenBounded_NoBlowup()
{
// A portal spanning from behind (z=+2) to in front (z=-5). The faithful clip keeps the
// in-front part and bounds it to the screen — no perspective-inversion blow-up, non-empty.
var poly = new[]
{
new Vector3(-1, -1, 2), new Vector3(1, -1, -5), new Vector3(1, 1, -5), new Vector3(-1, 1, 2),
};
var clip = PortalProjection.ProjectToClip(poly, Matrix4x4.Identity, ViewProj());
var ndc = PortalProjection.ClipToRegion(clip, FullScreenCcw());
Assert.True(ndc.Length >= 3);
foreach (var v in ndc) { Assert.InRange(v.X, -1.001f, 1.001f); Assert.InRange(v.Y, -1.001f, 1.001f); }
}
private static float AbsArea(Vector2[] p)
{
if (p == null || p.Length < 3) return 0f;
float a2 = 0f;
for (int i = 0; i < p.Length; i++) { var u = p[i]; var w = p[(i + 1) % p.Length]; a2 += u.X * w.Y - w.X * u.Y; }
return MathF.Abs(a2) * 0.5f;
}
[Fact]
public void ClipToRegion_SubjectFullyInsideRegion_ReturnsSubjectNotRegion()
{
// Regression for Build_AppliesReciprocalOtherPortalClip: a NARROW subject fully inside a WIDE
// region must return the narrow (subject ∩ region = subject), NOT the wide region. The builder's
// reciprocal clip is exactly this shape (reciprocal opening ∩ near-side region).
var view = Matrix4x4.CreateLookAt(Vector3.Zero, new Vector3(0, 0, -1), Vector3.UnitY);
var proj = Matrix4x4.CreatePerspectiveFieldOfView(1.2f, 1.0f, 0.1f, 1000f);
var vp = view * proj;
var narrow = new[] { new Vector3(-0.3f, -0.9f, -3f), new Vector3(0.3f, -0.9f, -3f), new Vector3(0.3f, 0.9f, -3f), new Vector3(-0.3f, 0.9f, -3f) };
var wide = new[] { new Vector3(-0.9f, -0.9f, -3f), new Vector3(0.9f, -0.9f, -3f), new Vector3(0.9f, 0.9f, -3f), new Vector3(-0.9f, 0.9f, -3f) };
var narrowClip = PortalProjection.ProjectToClip(narrow, Matrix4x4.Identity, vp);
// Build the region exactly as the builder does (clip wide against the full screen → CCW region).
var wideRegion = PortalProjection.ClipToRegion(PortalProjection.ProjectToClip(wide, Matrix4x4.Identity, vp), FullScreenCcw());
var clipped = PortalProjection.ClipToRegion(narrowClip, wideRegion);
float narrowArea = AbsArea(PortalProjection.ClipToRegion(narrowClip, FullScreenCcw()));
float wideArea = AbsArea(wideRegion);
float clippedArea = AbsArea(clipped);
Assert.True(clippedArea <= narrowArea + 1e-3f,
$"subject∩region must be the narrow subject (area {narrowArea}), not the wide region (area {wideArea}); got {clippedArea}");
}
[Fact]
public void ClipToRegion_AgainstSubRegion_TightensToIntersection()
{
// The region clip is the propagation step: clipping a wide on-screen portal against a
// narrower view region must yield the intersection (the narrow region), not the wide portal.
var wide = new[]
{
new Vector3(-2, -2, -5), new Vector3(2, -2, -5), new Vector3(2, 2, -5), new Vector3(-2, 2, -5),
};
var clip = PortalProjection.ProjectToClip(wide, Matrix4x4.Identity, ViewProj());
var narrow = new[]
{
new Vector2(-0.3f, -0.3f), new Vector2(0.3f, -0.3f), new Vector2(0.3f, 0.3f), new Vector2(-0.3f, 0.3f),
};
var ndc = PortalProjection.ClipToRegion(clip, narrow);
Assert.True(ndc.Length >= 3);
foreach (var v in ndc) { Assert.InRange(v.X, -0.301f, 0.301f); Assert.InRange(v.Y, -0.301f, 0.301f); }
}
// ---------------------------------------------------------------------------
// The W=0 knife-edge port (2026-06-11) — retail ACRender::polyClipFinish part 1
// (0x006b6d00, pc:702749; pseudocode at docs/research/2026-06-11-polyclipfinish-
// w0-clip-pseudocode.md). The eye-plane clip is at w >= 0 EXACTLY: boundary
// intersections land at w == 0 (homogeneous directions), so a portal the eye is
// CROSSING (stair openings on a spiral climb, the tower deck) yields the correct
// unbounded half-region that the bounded view-region clip then cuts to the
// screen. The previous EyePlaneW = 1e-4 made the boundary verts finite ~1e4-NDC
// points and the resulting regions sat at the merge/dedup degeneracy threshold —
// the climb-strobe class that the (now deleted) EyeInsidePortalOpening rescue
// compensated for.
// ---------------------------------------------------------------------------
[Fact]
public void ProjectToClip_EyeCrossingPortal_BoundaryVertsLandAtWZero()
{
// A horizontal floor opening 5 mm BELOW the eye, spanning from 1.5 m ahead to
// 0.5 m behind — the spiral-climb crossing frame. The two edges crossing the
// eye plane must emit intersections at exactly w == 0 (retail polyClipFinish
// t = w0/(w0-w1)), not at an epsilon offset.
var opening = new[]
{
new Vector3(-1f, -0.005f, -1.5f), new Vector3(1f, -0.005f, -1.5f),
new Vector3(1f, -0.005f, 0.5f), new Vector3(-1f, -0.005f, 0.5f),
};
var clip = PortalProjection.ProjectToClip(opening, Matrix4x4.Identity, ViewProj());
Assert.True(clip.Length >= 3, "an eye-crossing portal must keep its forward half");
int atZero = 0;
foreach (var v in clip)
{
Assert.True(v.W >= 0f, $"no survivor may sit behind the eye plane, got w={v.W}");
if (v.W == 0f) atZero++;
}
Assert.True(atZero >= 2, $"the two eye-plane crossings must land at exactly w==0, got {atZero}");
}
[Fact]
public void ClipToRegion_EyeCrossingFloorOpening_YieldsHalfRegionNotSliver()
{
// Same crossing frame: the visible set through an opening the eye is inside is
// the half-screen below the opening's plane horizon — NOT the degenerate sliver
// the epsilon clip produced. Full screen area is 4.0; the half-region must hold
// a substantial part of it.
var opening = new[]
{
new Vector3(-1f, -0.005f, -1.5f), new Vector3(1f, -0.005f, -1.5f),
new Vector3(1f, -0.005f, 0.5f), new Vector3(-1f, -0.005f, 0.5f),
};
var clip = PortalProjection.ProjectToClip(opening, Matrix4x4.Identity, ViewProj());
var ndc = PortalProjection.ClipToRegion(clip, FullScreenCcw());
Assert.True(ndc.Length >= 3, "the crossing frame must produce a region, not empty (the climb strobe)");
foreach (var v in ndc)
{
Assert.True(float.IsFinite(v.X) && float.IsFinite(v.Y), $"region verts must be finite, got ({v.X},{v.Y})");
Assert.InRange(v.X, -1.001f, 1.001f);
Assert.InRange(v.Y, -1.001f, 1.001f);
}
float area = AbsArea(ndc);
Assert.True(area > 1.5f,
$"the region must approximate the lower half-screen (area ~2.0 of 4.0), got {area} (sliver = the strobe bug)");
}
[Fact]
public void EyeInPortalPlane_GazeAlongPlane_DegenerateViewPropagates()
{
// The spiral-climb knife edge: the eye sits IN a horizontal portal's plane with
// the gaze ALONG the plane (climbing stairs through the opening). The opening is
// visibly edge-on ON screen: ProjectToClip + ClipToRegion yield a zero-area
// collinear region — and retail PROPAGATES it (ClipPortals forwards any count!=0
// clip; no area gate), keeping the cell behind in the draw list. CellView.Add
// must therefore ACCEPT the collinear polygon (the "L:" segment key) instead of
// rejecting it as degenerate — rejection dropped the whole chain for the frame.
var view = Matrix4x4.CreateLookAt(Vector3.Zero, new Vector3(0, 0, -1), Vector3.UnitY);
var proj = Matrix4x4.CreatePerspectiveFieldOfView(MathF.PI / 3f, 16f / 9f, 1.0f, 5000f);
var vp = view * proj;
// Horizontal opening in the y=0 plane (contains the eye), ahead of the camera.
var opening = new[]
{
new Vector3(-1f, 0f, -1f), new Vector3(1f, 0f, -1f),
new Vector3(1f, 0f, -4f), new Vector3(-1f, 0f, -4f),
};
var clip = PortalProjection.ProjectToClip(opening, Matrix4x4.Identity, vp);
Assert.True(clip.Length >= 3, "the in-plane opening's forward part must survive the W clip");
var ndc = PortalProjection.ClipToRegion(clip, FullScreenCcw());
Assert.True(ndc.Length >= 3, "the edge-on opening must yield its (zero-area) collinear region");
var cellView = new CellView();
Assert.True(cellView.Add(new ViewPolygon(ndc)),
"a zero-area collinear view must be ACCEPTED (retail propagates degenerate views; " +
"rejecting it drops the cell chain at the knife edge)");
// Re-emission of the same degenerate view dedups (finite segment-key space = convergence).
Assert.False(cellView.Add(new ViewPolygon(ndc)),
"a re-emitted degenerate view must dedup via its segment key");
}
[Fact]
public void ClipToRegion_NeverReturnsNonFiniteVerts()
{
// The measure-zero guard: whatever survives the bounded region clip must divide
// to finite NDC. Exercise with a portal whose vertices sit ON the eye plane
// (w == 0 inputs) plus one in front — degenerate input, must yield empty or finite.
var degenerate = new[]
{
new Vector3(-1f, 0f, 0f), new Vector3(1f, 0f, 0f), new Vector3(0f, 1f, -2f),
};
var clip = PortalProjection.ProjectToClip(degenerate, Matrix4x4.Identity, ViewProj());
if (clip.Length >= 3)
{
var ndc = PortalProjection.ClipToRegion(clip, FullScreenCcw());
foreach (var v in ndc)
Assert.True(float.IsFinite(v.X) && float.IsFinite(v.Y),
$"non-finite NDC vert leaked from the divide: ({v.X},{v.Y})");
}
}
}