Prepares a SceneKit object for rendering.
- iOS 8.0+
- macOS 10.9+
- Mac Catalyst 13.0+
- tvOS 9.0+
- watchOS 2.0+
A block that SceneKit calls periodically while preparing the object. The block takes no parameters.
Your block should return
NOto tell SceneKit to continue preparing the object, or
YESto cancel preparation.
nilfor this parameter if you do not need an opportunity to cancel preparing the object.
YES if the object was successfully prepared for rendering, or
NO if preparation was canceled.
By default, SceneKit lazily loads resources onto the GPU for rendering. This approach uses memory and GPU bandwidth efficiently, but can lead to stutters in an otherwise smooth frame rate when you add large amounts of new content to an animated scene. To avoid such issues, use this method to prepare content for drawing before adding it to the scene. You can call this method on a secondary thread to prepare content asynchronously.
SceneKit prepares all content associated with the
object parameter you provide. If you provide an
SCNMaterial object, SceneKit loads any texture images assigned to its material properties. If you provide an
SCNGeometry object, SceneKit loads all materials attached to the geometry, as well as its vertex data. If you provide an
SCNScene object, SceneKit loads all geometries and materials associated with the node and all its child nodes, or with the entire node hierarchy of the scene.
You can use the
block parameter to cancel preparation if content is no longer needed. For example, in a game you might use this method to preload areas of the game world the player is soon to enter, but if the player character dies before entering those areas, you can return
YES from the block to cancel preloading.
You can observe the progress of this operation with the
NSProgress class. For details, see