WaterCarve

Remarks

[35 § D5](../../docs/plan/35-water.md#d5-carving-is-a-reserved-edit-layer-and-the-machinery-exists), and the machinery existed. A third reserved layer alongside Splines and Scatter, on [31 § D4](../../docs/plan/31-terrain-grass-and-trees.md)'s contract and with no change to it — regenerated wholesale whenever a body changes, which is what makes it non-destructive. Unreal's water brush requires opting the landscape into edit layers, five years after Landscape shipped, which is why it is a setup step people miss; here they are the storage model, and water is the third consumer of a contract designed without it in mind.

The bed a body carves is the bed the field rasterises, by construction. Both read Sample — the surface height minus the coverage-weighted bed depth — so the shoreline the terrain is cut to and the shoreline the water is drawn at cannot disagree. That is § D2's argument applied to the ground rather than to the surface, and it is why this takes a WaterBody instead of a TerrainSplineProfile.

⚠ A river's channel is a band about its centreline and a lake's is its own polygon, and both come out of one call because Sample already knows which it is. Deforming a lake through TerrainSpline.Deform would cut a moat: that carves along a curve's width, and a closed curve's width is its shoreline, not its interior.

An island raises instead of lowering — Unreal's Invert Shape promoted to the thing it actually is, and the same sign flip Rasterize makes.

Fields and properties (1)

• public const string LayerName

  What the reserved layer is called.

Methods (3)

• public static TerrainEditLayer LayerOf(Terrain terrain, string name = "Water")

  The layer a terrain reserves for its water, adding it if there is not one.

• public static TerrainRect Carve(Terrain terrain, TerrainEditLayer layer, WaterBody body, in WaterCarveProfile profile)

  Cuts one body's bed into a layer.

• public static TerrainRect Regenerate(Terrain terrain, TerrainEditLayer layer, IEnumerable<(WaterBody Body, WaterCarveProfile Profile)> bodies)

  Empties the layer and lays every body down again.

Used by (2)

• WaterCarveTestsVixen.Water.Tests
• WaterCarveCommandVixen.Editor.Water