# centerOfMass The position of the center of mass and the orientation of the principal axes. ``` var centerOfMass: (position: SIMD3, orientation: simd_quatf) ``` ## Discussion The `position` defines the center of mass with a default value of `(0, 0, 0)`, which means that the local origin of the model is the center of mass. The `orientation` defines the principal axes, such the inertia matrix is a diagonal. --- 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)