WaterWaveSpectrum

Remarks

A spectrum and not a list ([35 § D7](../../docs/plan/35-water.md#d7-waves-are-a-spectrum-summed-as-gerstner-and-the-fft-is-deferred-with-arithmetic)). Wind, a spread, a wavelength range and a seed are the things somebody describing a sea has words for; sixteen amplitudes and phases are not.

⚠ Deterministic from Seed on every host, which is a stated exit criterion rather than a nicety: a client and a server that disagree about the sea disagree about where a boat is. Every draw goes through Hash, which is integer arithmetic and therefore the same everywhere there is a 32-bit word.

Why Gerstner and not an FFT. A sum of sixteen waves is a closed-form function of position and time, so a server can answer "where was the surface six ticks ago" without having simulated the intervening frames — which is what makes a rolled-back buoyancy force answerable at all. An FFT needs a per-frame dispatch chain and a CPU path that either reads back a texture or runs a second transform, and neither can answer that question. When the FFT lands it is a second model behind the same evaluator, and the seam test is what makes adding it safe.

Fields and properties (12)

• public float WindDirection

  Which way the wind blows, in radians about the vertical axis.

• public float WindSpeed

  How hard, in metres per second. Drives the amplitude and the wavelength range.

• public float DirectionalSpread

  How far off the wind a wave may travel, in radians. Zero is a perfectly ordered swell.

• public float MinimumWavelength

  The shortest wave in the sum, in metres.

• public float MaximumWavelength

  The longest, in metres.

• public float WavelengthFalloff

  How amplitude falls off toward the short end, as an exponent on the normalised wavelength.

• public float AmplitudeScale

  A multiplier on every amplitude the spectrum derives.

• public float Steepness

  How far the horizontal displacement goes, 0…1.

• public uint Seed

  Which sea, of all the seas with these numbers.

• public WaterWaveCount Count

  How many waves it is summed from.

• public static WaterWaveSpectrum Default

  An open sea in a fresh breeze: sixteen waves, half a metre of swell.

• public static WaterWaveSpectrum Calm

  A lake: eight short waves, almost no swell, and no wind direction worth having.

Methods (3)

• public string? Validate()

  Why this spectrum cannot be summed, or if it can.

• public int Generate(Span<GerstnerWave> into)

  Sums the spectrum into the waves the evaluator reads.

• public static float MaximumAmplitude(ReadOnlySpan<GerstnerWave> waves)

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

Used by (37)

• AssetWaterSourceVixen.Engine.Renderer
• AssetWaterSourceTestsVixen.Engine.Renderer.Tests
• IWaterWaveSourceVixen.Rendering.Water
• LakeVixen.Water.Physics.Tests
• SeaVixen.Rendering.Water.Tests
• SwellVixen.Water.Physics.Tests
• TypeRegistrationVixen.Rendering.Water
• UnderwaterPassTestsVixen.Rendering.Water.Tests
• UnderwaterShapeVixen.Rendering.Water
• UnderwaterShapeTestsVixen.Rendering.Water.Tests
• Vixen_Rendering_Water_WaterZoneComponentSerializerVixen.Rendering.Water
• Vixen_Water_WaterWaveSpectrumSerializerVixen.Water
• Vixen_Water_WaterWavesAssetSerializerVixen.Water
• WaterDebugDrawTestsVixen.Rendering.Water.Tests
• WaterEvaluatorTestsVixen.Water.Tests
• WaterHorizonImageTestsVixen.Graphics.Golden.Tests
• WaterMeshRendererVixen.Rendering.Water
• WaterQueryVixen.Water
• WaterSurfaceMeshTestsVixen.Water.Tests
• WaterSurfaceSeamDeviceTestsVixen.Graphics.Golden.Tests
• WaterWaveTestsVixen.Water.Tests
• WaterWavesAssetVixen.Water
• WaterZoneComponentVixen.Rendering.Water
• WaterZoneStateVixen.Water
• WaterZoneSystemVixen.Rendering.Water
• WaterZoneSystemTestsVixen.Rendering.Water.Tests
• WaterZoneTestsVixen.Water.Tests
• WavesEntryVixen.Engine.Renderer
• FileWavesVixen.Editor.Assets.Tests
• IWaterSceneVixen.Editor.SceneView
• WaterEditTestsVixen.Editor.Water.Tests
• WaterPresenterVixen.Editor.App
• WaterSceneSourceVixen.Editor.Water
• WaterWavesImporterVixen.Editor.Assets
• WaterWavesImporterTestsVixen.Editor.Assets.Tests
• WaterZoneSettingsVixen.Editor.Water
• WaveAdapterVixen.Editor.App