6c4b6d64d9
The user's "thin strip of background color along the TOP outer edge of a
doorway, looking out from inside" is the landscape-slice scissor box, not
the W=0 clip port.
Mechanism (pinned headlessly, Issue130DoorwayStripTests, 147 eye/gaze
combos at the real Holtburg A9B4 0x0170 exit door):
- BeginDoorwayScissor converted the slice NDC AABB to pixels as
Floor(origin) + Ceiling(size). The far edge floor(min)+ceil(max-min)
lands up to ONE PIXEL SHORT of the true top/right edge at unlucky
fractional alignments (captured: top edge y=0.7938 @1080p -> row 968
cut; right edge column 1296 @1920 cut).
- The scissor brackets the ENTIRE landscape slice (sky, terrain, outdoor
statics, weather). The exit-portal SEAL stamps the full raw aperture at
true depth and the shell wall ends at the aperture edge, so the cut row
never receives any color write -> clear color, flickering with eye
movement as the fractional alignment shifts.
- This violated AD-17's own invariant (over-inclusion is safe,
UNDER-inclusion is the bug class). No register change: the fix restores
the row's documented doctrine.
Lead 1 (987313a W=0 clip port regression) REFUTED by the same harness:
the CPU polygon pipeline (ProjectToClip -> ClipToRegion merges ->
ClipPlaneSet planes) is sub-pixel exact against the raw aperture
projection (worst 0.54 px, 0.00 px aligned). For an all-in-front doorway
polygon the port is bit-identical to the old 1e-4 path by construction.
The EyeInsidePortalOpening rescue stays deleted.
Fix: conservative outer bound floor(min)/ceil(max) extracted to
NdcScissorRect.ToPixels (GL-free; containment property proven in the
header comment); BeginDoorwayScissor delegates.
Pins:
- NdcScissorRectTests: center-inside containment across 251 fractional
alignments x 2 framebuffer sizes + both captured regression cases.
- Issue130DoorwayStripTests: production flood + assembler at the real
exit door; asserts the scissor never cuts a plane-admitted fragment
(worstScissorGap 0.00 px post-fix, was 10.8 px capped) and the CPU
pipeline stays sub-pixel exact (canary 1.2 px).
Suites: App 252+1skip / Core 1439+2skip / UI 420 / Net 294 green.
Awaiting the user visual gate at a cottage doorway.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
45 lines
2.3 KiB
C#
45 lines
2.3 KiB
C#
// NdcScissorRect.cs
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//
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// NDC AABB → framebuffer-pixel scissor box, CONSERVATIVE (outer bound).
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// The scissor that brackets a landscape/doorway slice is a fallback BOUND on
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// the slice's view region (AD-17 in the divergence register): it must CONTAIN
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// every fragment the per-fragment plane clip would keep. Under-inclusion is
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// the bug class — the #130 doorway top-edge background strip was this box
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// computed as Floor(origin) + Ceiling(size), whose far edge
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// floor(min)+ceil(max−min) lands up to one pixel SHORT of the true max edge
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// at unlucky fractional alignments, scissoring away the aperture's top/right
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// pixel row for the whole slice (sky, terrain, statics, weather) while the
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// seal still stamps it — a strip of clear color no later pass can fill.
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//
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// Correct outer bound: floor both mins, ceil both maxes, width = difference.
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// A fragment at pixel (i,j) rasterizes iff its CENTER (i+0.5, j+0.5) lies in
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// the region ⊆ the NDC box [X0,X1]×[Y0,Y1] (pixel units). Center-inside ⇒
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// i ≥ X0−0.5 ⇒ i ≥ floor(X0) and i ≤ X1−0.5 ⇒ i < ceil(X1). So
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// [floor(X0), ceil(X1)) admits every center-inside pixel, over-including by
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// at most one pixel per edge — safe per AD-17's doctrine (the wall shell /
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// plane clip repaints or kills the surplus).
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using System;
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using System.Numerics;
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namespace AcDream.App.Rendering;
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public static class NdcScissorRect
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{
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/// <summary>Convert an NDC AABB (minX, minY, maxX, maxY in [-1,1]) to a
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/// framebuffer-pixel scissor box that CONTAINS it. Inputs are clamped to
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/// the screen so a region extending past an edge still yields a valid box.
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/// Width/height are at least 1.</summary>
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public static (int X, int Y, int Width, int Height) ToPixels(
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Vector4 ndcAabb, int fbWidth, int fbHeight)
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{
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float nx0 = Math.Clamp(ndcAabb.X, -1f, 1f);
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float ny0 = Math.Clamp(ndcAabb.Y, -1f, 1f);
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float nx1 = Math.Clamp(ndcAabb.Z, -1f, 1f);
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float ny1 = Math.Clamp(ndcAabb.W, -1f, 1f);
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int px0 = (int)MathF.Floor((nx0 * 0.5f + 0.5f) * fbWidth);
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int py0 = (int)MathF.Floor((ny0 * 0.5f + 0.5f) * fbHeight);
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int px1 = (int)MathF.Ceiling((nx1 * 0.5f + 0.5f) * fbWidth);
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int py1 = (int)MathF.Ceiling((ny1 * 0.5f + 0.5f) * fbHeight);
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return (px0, py0, Math.Max(1, px1 - px0), Math.Max(1, py1 - py0));
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}
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}
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