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# VNTrackOpticalFlowRequest

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

```
class VNTrackOpticalFlowRequest
```

## 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()`](/documentation/Vision/VNTrackOpticalFlowRequest/init())

Creates a new request that tracks the optical from one image to another.

[`init(completionHandler:)`](/documentation/Vision/VNTrackOpticalFlowRequest/init(completionHandler:))

Creates a new request that tracks the optical from one image to another, with a system callback on completion.

### Configuring the Request

[`computationAccuracy`](/documentation/Vision/VNTrackOpticalFlowRequest/computationAccuracy-swift.property)

The level of accuracy to compute the optical flow.

[`VNTrackOpticalFlowRequest.ComputationAccuracy`](/documentation/Vision/VNTrackOpticalFlowRequest/ComputationAccuracy-swift.enum)

Computational accuracy options.

[`keepNetworkOutput`](/documentation/Vision/VNTrackOpticalFlowRequest/keepNetworkOutput)

A Boolean value that indicates the raw pixel buffer continues to emit from the network.

[`outputPixelFormat`](/documentation/Vision/VNTrackOpticalFlowRequest/outputPixelFormat)

The pixel format type of the output value.

### Accessing the Results

[`results`](/documentation/Vision/VNTrackOpticalFlowRequest/results)

The optical flow results the request observes.


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