# SCNSceneExportProgressHandler The signature for the block that SceneKit calls during scene export. ``` typealias SCNSceneExportProgressHandler = (Float, (any Error)?, UnsafeMutablePointer) -> Void ``` ## Discussion You specify a block with this signature when calling the [`write(to:options:delegate:progressHandler:)`](/documentation/SceneKit/SCNScene/write(to:options:delegate:progressHandler:)) method in order to receive updates on the progress of the export operation. The block takes the following parameters: - totalProgress: A number between `0.0` and `1.0` that indicates the progress of the export operation, with `0.0` indicating that the operation has just begun and `1.0` indicating the operation has completed. - error: An error encountered during the export process, or `nil` if no errors have occurred. - stop: Set `*stop` to inside the block to cancel export. --- 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)