Begins a new transaction for the current thread.
- iOS 8.0+
- macOS 10.8+
- tvOS 9.0+
- watchOS 3.0+
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.