TerrainEditLayer

Remarks

[docs/plan/31 § D4], and the reason it is the storage model rather than a feature on top of one. Unreal added edit layers seven years after Landscape shipped, which is why they are still opt-in per landscape there: everything written against the flat heightmap had to keep working. Building the composite in from the first commit means no tool ever has a flat-heightmap path to preserve, and the reserved-layer mechanism splines and scatter need is the same mechanism an author's own layers use.

Sparse, in chunks that are not tiles. A layer that touched three tiles stores three tiles' worth, and the allocation granularity is a fixed ChunkSize-square block of the global sample grid rather than a tile — deliberately, because chunks tile the grid without overlapping and tiles share their boundary rows. A chunk grid aligned to tiles would put the shared row in two chunks, which is [§ D2]'s seam bug reintroduced one level down.

Signed deltas in the same units as the samples. A delta of ±32 767 is half the height range, which is as much as any one layer has ever needed to move the ground, and it keeps a layer the same size as the base rather than twice it.

⚠ HeightAlpha is signed, and a negative one subtracts. That is Unreal's semantic and it is genuinely useful — the same sculpt inverted is a valley — but it means the composite has to clamp, and that the identity value is one rather than zero.

Fields and properties (12)

• public const int ChunkSize

  How many samples a sparse chunk is along each axis.

• public TerrainDescription Description

  The terrain's shape.

• public string Name

  What the layer is called.

• public TerrainLayerKind Kind

  Who owns its contents.

• public float HeightAlpha

  How much of its height deltas reach the composite. Signed; 1 is unchanged.

• public float WeightAlpha

  How much of its paint reaches the composite, 0…1.

• public bool IsVisible

  Whether it contributes at all.

• public bool IsLocked

  Whether it refuses edits.

• public bool AcceptsBrush

  Whether a tool may sculpt or paint into it by hand.

• public int ChunkCount

  How many chunks hold anything.

• public long Bytes

  How many bytes its deltas occupy.

• public bool IsEmpty

  Whether it has nothing in it.

Methods (8)

• public TerrainEditLayer(TerrainDescription description, string name, TerrainLayerKind kind = Manual)

  Creates an empty layer over a terrain's shape.

• public TerrainEditLayer Clone()

  A copy of the layer, deltas and all.

• public short DeltaAt(int x, int z)

  What this layer moves one sample by, before its alpha.

• public void SetDelta(int x, int z, short delta)

  Sets what this layer moves one sample by.

• public void AddDelta(int x, int z, int delta)

  Adds to what this layer moves one sample by, saturating rather than wrapping.

• public void Clear()

  Forgets everything the layer holds.

• public void Clear(TerrainRect rect)

  Forgets what the layer holds inside a rectangle.

• public IEnumerable<(int X, int Z)> OccupiedChunks()

  Which chunks hold anything, as their low corners in sample indices.

Used by (35)

• TerrainVixen.Terrain
• TerrainHeightmapVixen.Terrain
• TerrainHeightmapPngTestsVixen.Terrain.Tests
• TerrainHeightmapTestsVixen.Terrain.Tests
• TerrainLayerTestsVixen.Terrain.Tests
• TerrainLodTestsVixen.Terrain.Tests
• TerrainMipTestsVixen.Terrain.Tests
• TerrainPickTestsVixen.Terrain.Tests
• TerrainRendererTestsVixen.Rendering.Terrain.Tests
• TerrainResizeVixen.Terrain
• TerrainResizeTestsVixen.Terrain.Tests
• TerrainSculptVixen.Terrain
• TerrainSculptTestsVixen.Terrain.Tests
• TerrainSplineVixen.Terrain
• TerrainSplineTestsVixen.Terrain.Tests
• TerrainStoreVixen.Terrain
• TerrainStoreTestsVixen.Terrain.Tests
• TerrainStrokeVixen.Terrain
• TerrainStrokeRedoVixen.Terrain
• TerrainStrokeTestsVixen.Terrain.Tests
• TerrainSurfaceTestsVixen.Rendering.Terrain.Tests
• CollapseLayerCommandVixen.Editor.Terrain
• InsertLayerCommandVixen.Editor.Terrain
• LayerPropertyCommandVixen.Editor.Terrain
• RemoveLayerCommandVixen.Editor.Terrain
• ReplaceLayerCommandVixen.Editor.Terrain
• SculptSessionTestsVixen.Editor.Terrain.Tests
• TerrainEditVixen.Editor.Terrain
• TerrainEditTestsVixen.Editor.Terrain.Tests
• TerrainLayerCommandTestsVixen.Editor.Terrain.Tests
• TerrainLayerCommandsVixen.Editor.Terrain
• TerrainModeVixen.Editor.Terrain
• TerrainModuleVixen.Editor.Terrain
• TerrainPaintModeTestsVixen.Editor.Terrain.Tests
• TerrainStrokeCommandVixen.Editor.Terrain