Time & RNG

Trecs provides phase-aware time and deterministic random number generation.

Time properties

Access time values via the World accessor (available in systems):

Property	Description
DeltaTime	Time step for the current phase (fixed or variable)
FixedDeltaTime	Fixed timestep (default 1/60s)
VariableDeltaTime	Actual frame delta time
ElapsedTime	Total elapsed time for the current phase
FixedElapsedTime	Total fixed update time
VariableElapsedTime	Total variable update time
Frame	Frame counter for the current phase
FixedFrame	Fixed update frame counter
VariableFrame	Variable update frame counter

Phase-aware DeltaTime

DeltaTime returns the correct value for the system's phase:

// In a fixed update system: DeltaTime == FixedDeltaTime
public partial class PhysicsSystem : ISystem
{
    [ForEachEntity(MatchByComponents = true)]
    void Execute(ref Position pos, in Velocity vel)
    {
        pos.Value += vel.Value * World.DeltaTime;
    }
}

// In a variable update system: DeltaTime == VariableDeltaTime
[ExecuteIn(SystemPhase.Presentation)]
public partial class AnimationSystem : ISystem
{
    [ForEachEntity(MatchByComponents = true)]
    void Execute(ref AnimState state)
    {
        state.Time += World.DeltaTime;
    }
}

Fixed-time values are also accessible from variable update via World.FixedDeltaTime / World.FixedElapsedTime.

Deterministic RNG

Trecs provides a deterministic Rng seeded from WorldSettings.RandomSeed.

// Phase-aware (recommended)
float value = World.Rng.Next();          // [0, 1)
float range = World.Rng.NextFloat(0f, 10f);  // [min, max)

// Phase-specific
float fixedRand = World.FixedRng.Next();
float varRand = World.VariableRng.Next();

Fork the RNG for independent sub-sequences:

var forked = World.Rng.Fork();
// forked produces an independent stream; the call itself advances the parent

Set the seed for reproducible results:

var settings = new WorldSettings { RandomSeed = 42 };

Warning

For deterministic replay, always use World.Rng — never UnityEngine.Random or System.Random. External RNG sources are not captured in recordings.

Time in jobs

NativeWorldAccessor provides time values in Burst jobs:

float dt = nativeWorldAccessor.DeltaTime;
float elapsed = nativeWorldAccessor.ElapsedTime;