---
title: VNTrackOpticalFlowRequest
framework: vision
role: symbol
role_heading: Class
path: vision/vntrackopticalflowrequest
---

# VNTrackOpticalFlowRequest

An object that determines the direction change of vectors for each pixel from a previous to current image.

## Declaration

```swift
class VNTrackOpticalFlowRequest
```

## Overview

Overview This request works at the pixel level, so both images must have the same dimensions to successfully perform the request. Setting a region of interest isolates where to perform the change determination. important: Optical flow requests are very resource intensive, so perform only one request at a time. Release memory immediately after generating an optical flow.

## Topics

### Creating an Optical Flow

- [init()](vision/vntrackopticalflowrequest/init().md)
- [init(completionHandler:)](vision/vntrackopticalflowrequest/init(completionhandler:).md)

### Configuring the Request

- [computationAccuracy](vision/vntrackopticalflowrequest/computationaccuracy-swift.property.md)
- [VNTrackOpticalFlowRequest.ComputationAccuracy](vision/vntrackopticalflowrequest/computationaccuracy-swift.enum.md)
- [keepNetworkOutput](vision/vntrackopticalflowrequest/keepnetworkoutput.md)
- [outputPixelFormat](vision/vntrackopticalflowrequest/outputpixelformat.md)

### Accessing the Results

- [results](vision/vntrackopticalflowrequest/results.md)

## Relationships

### Inherits From

- [VNStatefulRequest](vision/vnstatefulrequest.md)

### Conforms To

- [CVarArg](swift/cvararg.md)
- [CustomDebugStringConvertible](swift/customdebugstringconvertible.md)
- [CustomStringConvertible](swift/customstringconvertible.md)
- [Equatable](swift/equatable.md)
- [Hashable](swift/hashable.md)
- [NSCopying](foundation/nscopying.md)
- [NSObjectProtocol](objectivec/nsobjectprotocol.md)

## See Also

### Optical flow

- [VNGenerateOpticalFlowRequest](vision/vngenerateopticalflowrequest.md)