WorldProperties class final

The properties of one world, read by everything in it.

One gravity per game (decision 1 of tasks/1.0-physics-audit.md). The engine's default is standardGravity; a game sets its own world explicitly where it stages it — the platformer's at 24 m/s², the racing game's at 20 — and a level may set its own on top (Level.world). Then a rigid body, a runner, an AI's jump arc, a ragdoll, a spark, a cloth, a tyre's grip and a swimmer's lift all read the same number, and a level set on the Moon is the Moon for every one of them.

The air's density is derived from its airTemperature and airPressure by the ideal gas law (airDensityAt) unless a world says it explicitly (airDensityOverride), and the speed of sound from its temperature (speedOfSound).

The medium is a material's id in the engine's MaterialCatalog: f3d.air for a world on land, f3d.seawater for one under the sea, a plugin's for one of its own. What a body moving through the world is dragged and lifted by is mediumDensity — the world's own air where the medium is air, the catalogue's entry otherwise.

What its numbers promise is its profile: the deterministic one, bit for bit on every platform, unless a laboratory or a twin asks for the accurate one. A body's integrator reads the profile's capabilities here, where it reads gravity.

Where it is on the Earth, when it is somewhere: geoOrigin, the latitude, longitude and altitude its origin stands on, its axes east, up and south.

Not how often it is stepped. A world's step rate is the loop's (WorldTiming in flutter3d_sim); it was a field here until 1.0.0-rc.1, which nothing read, and a document that still carries it reads with the key passed over.

Immutable: a world that changes takes a new value (copyWith), and a snapshot holds one (toJson). gravity and wind are vector_math vectors, which are mutable, so the world keeps its own copies and hands out fresh ones. See docs/CONTRACTS.md's "World properties" for who reads each field.

Constructors

WorldProperties({Vector3? gravity, double airTemperature = standardAirTemperature, double airPressure = standardAtmosphere, double? airDensity, double airHumidity = standardRelativeHumidity, Vector3? wind, String medium = 'f3d.air', SimulationProfile profile = SimulationProfile.deterministic, GeoOrigin? geoOrigin}): A world with these properties; anything left out is the standard world's (standard_world.dart). Throws an ArgumentError for a temperature, pressure or density that is not finite and positive, or a gravity or wind that is not finite.
WorldProperties.fromJson(Map<String, Object?> json, {WorldProperties? base}): The world json describes, each field absent taken from base — the standard world by default, a game's own world when a level overrides only some of it.
factory

Properties

airDensity → double: The air's density, kg/m³: airDensityOverride, or the ideal gas's at airTemperature and airPressure (airDensityAt) — standardAirDensity for the standard air, to the bit.
no setter
airDensityOverride → double?: The air's density a world set explicitly, kg/m³; null when it is derived (airDensity).
final
airHumidity → double: The air's relative humidity, nought to one: the water vapour it holds over what it holds saturated at airTemperature. What open liquid evaporates into, and the vapour's part of a fluid world's air (FluidAir in flutter3d_physics); standardRelativeHumidity by default. airDensity stays dry air's, which every recorded run was made with.
final
airPressure → double: The air's pressure at the world's datum — the surface of its sea, the floor of its valley — Pa.
final
airTemperature → double: The air's temperature, K.
final
geoOrigin → GeoOrigin?: Where the world's origin is on the Earth, or null for a world that is nowhere in particular: a game's level, a laboratory's bench.
final
gravity → Vector3: Metres per second squared; standardGravity down y by default. A fresh vector each call: a Vector3 is mutable.
no setter
gravityMagnitude → double: How strong gravity is, m/s². standardGravity to the bit for the standard gravity, as NativeWorld.gravityMagnitude is.
no setter
hashCode → int: The hash code for this object.
no setteroverride
medium → String: The id of the material the world is filled with, in its MaterialCatalog: f3d.air by default.
final
profile → SimulationProfile: What the world's numbers promise: SimulationProfile.deterministic by default. Code that decides by it asks a capability (profile.usesDoublePrecision), never which profile it is.
final
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited
speedOfSound → double: How fast sound travels in the world's air, m/s (speedOfSoundAt its temperature): what a listener's Doppler shift is reckoned against.
no setter
wind → Vector3: The wind everywhere, m/s: what a cloth flaps in, smoke and sparks drift on and the air drags a body by. A fresh vector each call.
no setter

Methods

copyWith({Vector3? gravity, double? airTemperature, double? airPressure, double? airDensity, bool clearAirDensity = false, double? airHumidity, Vector3? wind, String? medium, SimulationProfile? profile, GeoOrigin? geoOrigin, bool clearGeoOrigin = false}) → WorldProperties: A copy with the fields given changed. clearAirDensity goes back to deriving the air's density from its temperature and pressure.
mediumDensity(MaterialCatalog catalog) → double: The density of what a body moving through the world is dragged and lifted by, kg/m³: airDensity when the medium is f3d.air, else the medium's in catalog. Throws an UnknownMaterialException naming the plugin it needs when catalog has no such material, and a StateError for a medium with no density.
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
inherited
toJson() → Map<String, Object?>: The world as JSON, every field: what a snapshot and a level hold. airDensity only when airDensityOverride says it; airHumidity only when it is not standardRelativeHumidity, profile only when it is not SimulationProfile.deterministic and geoOrigin only when there is one, so the default world is written, and digested, as it was before any of them existed.
toString() → String: A string representation of this object.
override

Operators

operator ==(Object other) → bool: The equality operator.
override

Static Properties

standard → WorldProperties: The standard world: standardGravity down, the air of a room at sea level, no wind, in air.
final