---
title: "init(trajectoryLength:_:frameAnalysisSpacing:)"
framework: vision
role: symbol
role_heading: Initializer
path: "vision/detecttrajectoriesrequest/init(trajectorylength:_:frameanalysisspacing:)"
---

# init(trajectoryLength:_:frameAnalysisSpacing:)

Creates a trajectory-detection request.

## Declaration

```swift
init(trajectoryLength: Int, _ revision: DetectTrajectoriesRequest.Revision? = nil, frameAnalysisSpacing: CMTime? = nil)
```

## Parameters

- `trajectoryLength`: The number of points required to analyze to determine that a shape follows a parabolic path. This argument value must be at least 5.
- `revision`: The specific algorithm or implementation revision that the system uses to perform the request.
- `frameAnalysisSpacing`: The duration between analysis operations. Increase this value to reduce the number of frames analyzed on slower devices. By default, Vision analyzes all frames.