# ConstantForceEffect A force effect that exerts a constant force in a direction relative to the effect’s transform. ``` struct ConstantForceEffect ``` ## Topics ### Initializers [`init(strength: Double, direction: SIMD3)`](/documentation/RealityKit/ConstantForceEffect/init(strength:direction:)) Creates a constant force effect. ### Instance Properties [`let direction: SIMD3`](/documentation/RealityKit/ConstantForceEffect/direction) The direction of the force relative to the effect’s transform. [`var forceMode: ForceMode`](/documentation/RealityKit/ConstantForceEffect/forceMode) The type of force this effect applies. [`var parameterTypes: PhysicsBodyParameterTypes`](/documentation/RealityKit/ConstantForceEffect/parameterTypes) The input rigid body parameters. [`let strength: Float`](/documentation/RealityKit/ConstantForceEffect/strength) The magnitude of the force. ### Instance Methods [`func update(parameters: inout ForceEffectParameters)`](/documentation/RealityKit/ConstantForceEffect/update(parameters:)) Calculates the constant forces for rigid bodies from the force effect. ## Relationships ### Conforms To [`Decodable`](/documentation/Swift/Decodable) [`Encodable`](/documentation/Swift/Encodable) [`ForceEffectProtocol`](/documentation/RealityKit/ForceEffectProtocol) --- 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)