---
title: PhysicsSimulationEvents.WillSimulate
framework: realitykit
role: symbol
role_heading: Structure
path: realitykit/physicssimulationevents/willsimulate
---

# PhysicsSimulationEvents.WillSimulate

The event raised before the simulation advances to the current frame.

## Declaration

```swift
struct WillSimulate
```

## Topics

### Instance Properties

- [deltaTime](realitykit/physicssimulationevents/willsimulate/deltatime.md)
- [simulationEntity](realitykit/physicssimulationevents/willsimulate/simulationentity.md)
- [simulationRootEntity](realitykit/physicssimulationevents/willsimulate/simulationrootentity.md)

## Relationships

### Conforms To

- [Event](realitykit/event.md)
- [Sendable](swift/sendable.md)
- [SendableMetatype](swift/sendablemetatype.md)