# Simulate

> Simulate the world. If deltaTime is zero then only contact and trigger events will be updated and no velocity or position integration or constraint updates will occur.

## Definition

* **Type:** Method
* **Namespace:** [Unity.U2D.Physics](/engine/6000.5/script-reference/unity/u2d/physics.md)
* **Assembly:** UnityEngine.PhysicsCore2DModule

## Simulate(float)

Simulate the world. If `deltaTime` is zero then only contact and trigger events will be updated and no velocity or position integration or constraint updates will occur.

```csharp
public void Simulate(float deltaTime)
```

### Parameters

**** (\[float]\(https\://learn.microsoft.com/dotnet/api/system.single)): The amount of time to forward simulate the world.

## Simulate(ReadOnlySpan\<PhysicsWorld>, float)

Simulate a batch of worlds. If `deltaTime` is zero then only contact and trigger events will be updated and no velocity or position integration or constraint updates will occur. The worlds can be simulated concurrently depending on the setting of [\_concurrentSimulations](/engine/6000.5/script-reference/unity/u2d/physics/physicscoresettings2d/concurrentsimulations.md).

```csharp
public static void Simulate(ReadOnlySpan<PhysicsWorld> worlds, float deltaTime)
```

### Parameters

**** (\[ReadOnlySpan\<PhysicsWorld>]\(https\://learn.microsoft.com/dotnet/api/system.readonlyspan-1)): The worlds to forward simulate.**** (\[float]\(https\://learn.microsoft.com/dotnet/api/system.single)): The amount of time to forward simulate the world.