WaterSurfaceMesh

Remarks

The terrain's quadtree with a different height source ([35 § D4](../../docs/plan/35-water.md#d4-the-surface-is-the-terrains-quadtree-with-a-different-height-source)). PatchSelector selects the nodes, morphs them and guarantees no cracks; every word of the terrain's CDLOD argument is true of water, and the only difference is what the vertex stage samples for height — a heightmap mip chain there, the info field plus the wave sum here. Unreal has two quadtrees, two morph implementations and two sets of debug commands; this is the other answer.

The finest node's vertex spacing is the info field's texel spacing, by construction. The root spans the window's Resolution − 1 quads rounded up to whole patches, so a 512 m window at 257 texels gives 256 quads at two metres — one vertex per texel at level zero. Any other choice makes the surface either carry detail the field cannot supply or throw away detail it can.

⚠ The node's error metric includes the sea state's maximum amplitude, not just the height range. § D4 asks for "density where the waves are, not where the ground is", and the bound is the harder half of it: a node bounded by its rest height is a node culled away while a crest is still in front of the camera, and the symptom is a strip of missing sea that appears only in a swell.

Fields and properties (8)

• public WaterFieldDescription Window

  The window the mesh covers. Its origin follows the field's.

• public int GridQuads

  How many quads the shared grid patch spans.

• public float MetresPerQuad

  How many metres one quad of the finest level covers.

• public PatchSelector Selector

  The descent, shared with the terrain.

• public TerrainLodRanges Ranges

  Where each level takes over.

• public float MaximumAmplitude

  The tallest the sea state can be above its rest height, in metres.

• public float FarDistance

  How far past the window the far mesh reaches, in metres.

• public float EdgeFade

  How wide the band is over which the waves fade out at the window's edge, in metres.

Methods (7)

• public WaterSurfaceMesh(in WaterFieldDescription window, TerrainLodRanges ranges, int gridQuads = 32)

  Builds a mesh over a window's shape.

• public void Update(WaterFieldPyramid reduced, float maximumAmplitude)

  Points the mesh at a field, and tells it how tall the sea is.

• public int Select(Vector3 viewPosition, in BoundingFrustum frustum, ICollection<TerrainLodNode> nodes)

  Chooses the patches inside the window a view draws.

• public int SelectFar(in BoundingFrustum frustum, float restHeight, ICollection<TerrainLodNode> nodes)

  Chooses the skirt patches beyond the window — the far mesh.

• public Vector2 GroundOf(in TerrainLodNode node, int gridX, int gridZ)

  Where one vertex of a patch lands on the ground plane, after morphing.

• public float EdgeDamping(Vector2 position)

  How much of the sea state survives at a place, before the depth attenuation.

• public (Vector3 Position, Vector3 Normal) PositionOf(in TerrainLodNode node, int gridX, int gridZ, in WaterEvaluator evaluator, float waterTime)

  Where one vertex of a patch lands in the world, waves included.

Used by (8)

• WaterDebugDrawVixen.Rendering.Water
• WaterDebugDrawTestsVixen.Rendering.Water.Tests
• WaterMeshRendererVixen.Rendering.Water
• WaterSurfaceMeshTestsVixen.Water.Tests
• WaterSurfacePassVixen.Rendering.Water
• WaterSurfacePassTestsVixen.Rendering.Water.Tests
• WaterZoneDrawVixen.Rendering.Water
• ZoneVixen.Rendering.Water