---
title: "createReferenceObject(transform:center:extent:completionHandler:)"
framework: arkit
role: symbol
role_heading: Instance Method
path: "arkit/arsession/createreferenceobject(transform:center:extent:completionhandler:)"
---

# createReferenceObject(transform:center:extent:completionHandler:)

Creates a reference object (for 3D object detection) from the specified region of the session’s world space.

## Declaration

```swift
func createReferenceObject(transform: simd_float4x4, center: simd_float3, extent: simd_float3, completionHandler: @escaping @Sendable (ARReferenceObject?, (any Error)?) -> Void)
```

```swift
func createReferenceObject(transform: simd_float4x4, center: simd_float3, extent: simd_float3) async throws -> ARReferenceObject
```

## Parameters

- `transform`: A transform matrix defining the origin and orientation of the local coordinate system for the region to extract.
- `center`: A point, relative to the origin specified by transform, that defines the center of the bounding box for the region to extract.
- `extent`: The width, height, and depth of the region to extract, centered on the center point and oriented to the local coordinate system specified by transform.
- `completionHandler`: A handler to be invoked asynchronously after ARKit finishes creating the reference object. The handler takes two parameters:

## Discussion

Discussion important: This method is valid only when running a session with ARObjectScanningConfiguration, which enables the high-fidelity spatial data collection needed for scanning reference objects. Calling this method on a session with a different configuration immediately invokes your completionHandler with an error. To use the extracted reference object for 3D object detection, assign it to the detectionObjects property of a world tracking configuration. You can bundle reference objects in an app by saving them to files and adding them to an Xcode asset catalog. When ARKit detects a reference image, the transform of the resulting ARObjectAnchor is based on the orgin of the reference object’s coordinate system—the transform you specify when extracting the reference object. For example, if a reference object represents a physical item that sits on a horizontal surface, virtual content should appear to sit on whatever surface the physical object does. To adjust a reference object’s origin after extracting it, use the applyingTransform(_:) method.