# setForce(_:index:) Sets the force for each rigid body. ``` func setForce(_ force: SIMD3, index: Int) ``` ## Parameters `force` The force value. `index` The index to the rigid body. The index should be in the range [0, [`physicsBodyCount`](/documentation/RealityKit/ForceEffectParameters/physicsBodyCount)]. ## Discussion Inside the force effect update function, you are responsible to compute and output the force by calling this function for each rigid body. If you omit this function for a rigid body, that rigid body gets zero force from the effect. --- 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)