# ForceEffectComponent A component that defines the forces that affect an entity, including custom forces that you define. ``` struct ForceEffectComponent ``` ## Overview After you assign a `ForceEffectComponent` to an entity, the force effects in the component apply each physics update for as long as the component and force effects exist. Each [`ForceEffect`](/documentation/RealityKit/ForceEffect) updates sequentially while the physics system accumulates its forces. The center frame of each [`ForceEffect`](/documentation/RealityKit/ForceEffect) coincides with and moves alongside the entity’s position and orientation. To offset this center frame, set the position and orientation. > Note: You can set the ``doc://com.apple.RealityKit/documentation/RealityKit/ForceEffectComponent/simulationState-swift.property`` parameter to ``doc://com.apple.RealityKit/documentation/RealityKit/ForceEffectComponent/SimulationState-swift.enum/pause`` if you want to apply forces later. ### Create forces Use [`ConstantForceEffect`](/documentation/RealityKit/ConstantForceEffect) to apply a constant force in a direction: ```swift let constantForceEffect = ForceEffect(effect: ConstantForceEffect(strength: 1, direction: [1, 0, 0])) ``` RealityKit provides a set of useful forces you can use with `ForceEffectComponent`: - [`ConstantForceEffect`](/documentation/RealityKit/ConstantForceEffect) - [`ConstantRadialForceEffect`](/documentation/RealityKit/ConstantRadialForceEffect) - [`DragForceEffect`](/documentation/RealityKit/DragForceEffect) - [`RadialForceEffect`](/documentation/RealityKit/RadialForceEffect) - [`TurbulenceForceEffect`](/documentation/RealityKit/TurbulenceForceEffect) - [`VortexForceEffect`](/documentation/RealityKit/VortexForceEffect) ### Create custom forces To create a custom force effect, define a structure that implements [`ForceEffectProtocol`](/documentation/RealityKit/ForceEffectProtocol), then create an instance of [`ForceEffectBase`](/documentation/RealityKit/ForceEffectBase) with your custom `ForceEffectProtocol` implementation: ```swift // CustomForce implements ForceEffectProtocol, and has a custom parameter, thrustersActive, that determines how the system applies your force to a physics body. let thrusterForce = CustomForce(thrustersActive: true) // Create an instance of ForceEffectBase using your custom force. let thursterForceEffect = ForceEffect(effect: thrusterForce) ``` > Note: To apply force to a physics body with a custom `ForceEffectProtocol`, you must implement and apply forces in ``doc://com.apple.RealityKit/documentation/RealityKit/ForceEffectProtocol/update(parameters:)``. ### Apply forces You can apply multiple forces to your entity at once by including them in `ForceEffectComponent`: ```swift let forceEffectComponent = ForceEffectComponent(effects: [constantForceEffect, thrusterForceEffect]) entity.components.set(forceEffectComponent) ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)