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fix(render): doorway void — portal near-clip was near-dependent (eye-clip instead)

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The cottage doorway 'void' (dark cell + floating entities while the chase camera looks
through the opening): PortalProjection.ProjectToNdc clipped portals on w+z>=0 — the GL
[-1,1] near-plane test — but acdream's camera builds its projection with D3D-convention
Matrix4x4.CreatePerspectiveFieldOfView and a 1.0 m near plane (RetailChaseCamera). Against
that matrix w+z>=0 discards everything within ~0.5 m of the eye, so when the camera orbits
to ~0.1 m from a doorway portal the near edge is clipped, the far edge projects off-screen
([flap] showed p->0171 D=0.10 proj=4 clip=0 ndc Y=-3.5..-6.6), the room behind is culled
(vis=1) and only the tiny vestibule shell draws -> dark void. Rotating away moved the eye
off the portal -> vis=5 -> room rendered.

Fix: clip against the EYE (w > MinW, MinW=0.05 m), near-INDEPENDENT — a portal you're
standing in still projects (covers the screen) so the cell behind stays visible. We only
use the projected x/y for the visibility clip region, so keeping vertices in front of the
near plane is correct. Matches retail PView::GetClip near-clipping the portal before project.
RED->GREEN regression test (doorway 0.1 m from a near=1.0 eye); 177 App tests green; the
existing straddling ±50 bound still holds.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-06-03 13:42:46 +02:00
parent 1e9a9cab8c
commit 0cc561c4d0
2 changed files with 61 additions and 16 deletions
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32
tests/AcDream.App.Tests/Rendering/PortalProjectionTests.cs
View file

@ -1,3 +1,4 @@
using System;
using System.Numerics;
using AcDream.App.Rendering;
using Xunit;
@ -84,4 +85,35 @@ public class PortalProjectionTests
Assert.InRange(v.Y, -1.001f, 1.001f);
}
}
[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)");
}
}