fix: heightmap transpose + solid-color + translucency + clipmap textures
Three root causes found via systematic debugging after the user reported that thedc60405texture fix and4763b97height table fix had no visible effect on Holtburg. ## Heightmap transpose (LandblockMesh.Build) Phase 1's LandblockMesh.Build indexed block.Height as y*9+x but AC packs per-vertex heights in x-major order (x*9+y, matching ACViewer's LandblockStruct: Height[x * VertexDim + y]). The bug was invisible on flat landblocks (Phase 1 smoke test) but left buildings buried by 10-13 world-Z units on Holtburg, because building Frame.Origin positions reference the un-transposed ground truth. Diagnostic evidence (before fix, Holtburg 0xA9B4FFFF): entity 0x020000A5 at ( 84.6,126.0) entityZ= 66.03 terrainZ= 78.15 delta=-12.13 entity 0x02000118 at ( 74.2,139.9) entityZ= 66.03 terrainZ= 78.92 delta=-12.89 After fix: deltas are 0.03 to 2.18 — buildings now sit on the ground with small positive offsets for foundations. Regression test added: Build_HeightmapPackedAsXMajor_NotYMajor asserts asymmetric heights land at the correct world positions. ## Solid-color surfaces with Translucency=1.0 (SurfaceDecoder.DecodeSolidColor) The "bright pink doors and windows" the user saw were 11 Holtburg surfaces with OrigTextureId==0 — these carry a ColorValue instead of a texture chain. Phase 2a's TextureCache dropped them into the magenta fallback. All 11 turned out to be Base1Solid|Translucent with Translucency=1.00, meaning "fully transparent placeholder surface" (debug ColorValue is gray/green/red/blue/black, never displayed). DecodeSolidColor now takes a translucency parameter and multiplies alpha by (1 - translucency), so Translucency=1.0 → alpha=0, and the mesh shader's existing alpha discard (< 0.5) makes the pixel invisible. TextureCache honors Surface.Type.HasFlag(Base1Solid) and passes surface.Translucency through. Regression tests added: DecodeSolidColor_Opaque_PreservesAlpha and DecodeSolidColor_FullyTranslucent_AlphaGoesToZero. ## Clipmap alpha-key (DecodeIndex16) AC convention (per ACViewer TextureCache.IndexToColor): on surfaces marked Base1ClipMap, palette indices 0..7 are treated as fully transparent regardless of their actual palette color. Without this, low-index pixels on clipmap surfaces (typically doorway cutouts and foliage) render as opaque using whatever sentinel color is at those palette slots. DecodeRenderSurface now takes an isClipMap parameter. TextureCache passes Surface.Type.HasFlag(Base1ClipMap). DecodeIndex16 forces rgba=(0,0,0,0) when isClipMap && idx < 8. Regression test added: DecodeIndex16_ClipMap_ZerosAlphaForLowIndices. ## Notes - dc60405's PFID_INDEX16 palette decoder remains correct — no change. - 4763b97's LandHeightTable wiring remains correct — real-table lookup still runs, it just happens to be linear at Holtburg's height range. The fix is forward-compatible with mountains elsewhere. - All three bugs were invisible to the original unit tests. The new regression tests pin them down. ## State - dotnet build: 0 warnings, 0 errors - dotnet test: 42 passing (was 38 + 4 new) - Runtime: 126 entities hydrated on Holtburg, no exceptions, no magenta fallback (counter was 11, now 0 via diagnostic confirmation) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Erik
parent
dc60405ebc
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5 changed files with 154 additions and 14 deletions
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@ -81,4 +81,30 @@ public class LandblockMeshTests
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// AC's Land::LandHeightTable scales height byte index by 2.0f for the simple ramp case.
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Assert.Equal(10.0f, mesh.Vertices[0].Position.Z);
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}
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[Fact]
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public void Build_HeightmapPackedAsXMajor_NotYMajor()
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{
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// Regression: Phase 1 used block.Height[y*9+x] which transposes the terrain
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// along its diagonal relative to AC's native x-major packing. Invisible on
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// flat landblocks but catastrophically wrong on Holtburg where static-object
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// positions reference the un-transposed ground truth, leaving buildings
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// buried by ~10 world-Z units.
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//
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// Set up an asymmetric heightmap: value at x-major index (x=2, y=0) = 5
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// (scaled to Z=10), everything else 0. The vertex at world position
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// (x=2*24=48, y=0) should have Z=10. The vertex at (x=0, y=2*24=48) should
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// have Z=0. Y-major indexing would swap these.
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var block = BuildFlatLandBlock();
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block.Height[2 * 9 + 0] = 5; // x=2, y=0 in x-major packing
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var mesh = LandblockMesh.Build(block, IdentityHeightTable);
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// Find vertices by position. Vertex buffer uses y*9+x internally.
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var vAt_x2_y0 = mesh.Vertices[0 * 9 + 2]; // world (48, 0)
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var vAt_x0_y2 = mesh.Vertices[2 * 9 + 0]; // world (0, 48)
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Assert.Equal(new Vector3(48, 0, 10), vAt_x2_y0.Position);
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Assert.Equal(new Vector3(0, 48, 0), vAt_x0_y2.Position);
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}
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}
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@ -1,6 +1,7 @@
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using AcDream.Core.Textures;
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using DatReaderWriter.DBObjs;
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using DatReaderWriter.Enums;
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using DatReaderWriter.Types;
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namespace AcDream.Core.Tests.Textures;
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@ -86,4 +87,64 @@ public class SurfaceDecoderTests
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Assert.Same(DecodedTexture.Magenta, decoded);
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}
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[Fact]
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public void DecodeSolidColor_Opaque_PreservesAlpha()
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{
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var color = new ColorARGB { Alpha = 0xFF, Red = 0x11, Green = 0x22, Blue = 0x33 };
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var decoded = SurfaceDecoder.DecodeSolidColor(color, translucency: 0f);
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Assert.Equal(1, decoded.Width);
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Assert.Equal(1, decoded.Height);
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Assert.Equal(new byte[] { 0x11, 0x22, 0x33, 0xFF }, decoded.Rgba8);
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}
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[Fact]
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public void DecodeSolidColor_FullyTranslucent_AlphaGoesToZero()
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{
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// Surfaces marked Base1Solid + Translucent with Translucency=1.0 are
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// AC's convention for "invisible placeholder surfaces" — the engine renders
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// them as nothing. Alpha must go to 0 so the mesh shader's discard rule
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// makes them invisible.
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var color = new ColorARGB { Alpha = 0xFF, Red = 0xC8, Green = 0xC8, Blue = 0xC8 };
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var decoded = SurfaceDecoder.DecodeSolidColor(color, translucency: 1f);
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Assert.Equal(0, decoded.Rgba8[3]); // alpha must be zero
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}
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[Fact]
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public void DecodeIndex16_ClipMap_ZerosAlphaForLowIndices()
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{
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// Build a 4x1 INDEX16 surface with indices 0, 1, 7, 8.
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// On a clipmap surface, indices 0..7 should be fully transparent and
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// index 8 should render with its palette color.
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var rs = new RenderSurface
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{
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Width = 4,
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Height = 1,
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Format = PixelFormat.PFID_INDEX16,
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SourceData = new byte[]
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{
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0x00, 0x00, // index 0
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0x01, 0x00, // index 1
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0x07, 0x00, // index 7
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0x08, 0x00, // index 8
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},
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};
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var palette = new Palette();
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for (int i = 0; i < 16; i++)
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palette.Colors.Add(new ColorARGB { Alpha = 0xFF, Red = 0xAA, Green = 0xBB, Blue = 0xCC });
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var decoded = SurfaceDecoder.DecodeRenderSurface(rs, palette, isClipMap: true);
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// Pixels 0, 1, 2 (indices 0, 1, 7) should be fully transparent.
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Assert.Equal(0, decoded.Rgba8[3]); // pixel 0 alpha
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Assert.Equal(0, decoded.Rgba8[7]); // pixel 1 alpha
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Assert.Equal(0, decoded.Rgba8[11]); // pixel 2 alpha
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// Pixel 3 (index 8) should have the palette alpha.
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Assert.Equal(0xFF, decoded.Rgba8[15]);
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Assert.Equal(0xAA, decoded.Rgba8[12]);
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}
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}
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