<!--
{
  "availability" : [
    "iOS: 18.0.0 -",
    "iPadOS: 18.0.0 -",
    "macOS: 15.0.0 -",
    "tvOS: 18.0.0 -",
    "visionOS: 2.0.0 -",
    "watchOS: 27.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "Vision",
  "identifier" : "/documentation/Vision/DetectTrajectoriesRequest/init(trajectoryLength:_:frameAnalysisSpacing:)",
  "metadataVersion" : "0.1.0",
  "role" : "Initializer",
  "symbol" : {
    "kind" : "Initializer",
    "modules" : [
      "Vision"
    ],
    "preciseIdentifier" : "s:6Vision25DetectTrajectoriesRequestC16trajectoryLength_20frameAnalysisSpacingACSi_AC8RevisionOSgSo6CMTimeaSgtcfc"
  },
  "title" : "init(trajectoryLength:_:frameAnalysisSpacing:)"
}
-->

# init(trajectoryLength:_:frameAnalysisSpacing:)

Creates a trajectory-detection request.

```
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.

---

Copyright &copy; 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)