---
title: checkpointDirectory
framework: realitykit
role: symbol
role_heading: Instance Property
path: realitykit/photogrammetrysession/configuration-swift.struct/checkpointdirectory
---

# checkpointDirectory

The directory that a the photogrammetry session uses for checkpoints during reconstruction.

## Declaration

```swift
var checkpointDirectory: URL?
```

## Discussion

Discussion For macOS reconstruction, the checkpointDirectory serves as a temporary reconstruction space if it is not nil. Reconstruction starts from scratch, and does not resume from previous checkpoints. For iOS reconstruction, if you pass the same checkpointDirectory used by an ObjectCaptureSession or an earlier interrupted PhotogrammetrySession, the PhotogrammetrySession tries to use the saved checkpoint instead of starting from scratch. Ensure that each checkpointDirectory is unique for each images folder. If set to an empty folder, the checkpointDirectory saves checkpoints during processing for reuse in a subsequent restart. If it is nil, the session does not use or save checkpoints, and every reconstruction starts from scratch. If a checkpointDirectory is has a non-nil value, but the latest checkpoint is not compatible with the images folder or other configuration settings, the session starts from scratch and writes new checkpoints to this folder.