# begin() Begins a new transaction for the current thread. ``` class func begin() ``` ## Discussion The new transaction is nested within the thread’s current transaction, if there is one. The first time you modify the scene graph during a pass through the run loop, SceneKit automatically creates a transaction and makes it the current transaction. (SceneKit commits that transaction when the next iteration of the run loops begins.) If you call this method to create a custom transaction before modifying the scene graph, your custom transaction becomes the current transaction. --- 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)