Class ARSessionOrigin

An ARSessionOrigin is the parent for an AR setup. It contains a Camera and any GameObjects created from detected features, such as planes or point clouds.

Inheritance
object
Object
Component
Behaviour
MonoBehaviour
ARSessionOrigin
Inherited Members
Object.FindObjectsByType<T>(FindObjectsSortMode)
Object.FindObjectsByType<T>(FindObjectsInactive, FindObjectsSortMode)
Object.FindFirstObjectByType<T>()
Object.FindAnyObjectByType<T>()
Object.FindFirstObjectByType<T>(FindObjectsInactive)
Object.FindAnyObjectByType<T>(FindObjectsInactive)
Namespace: UnityEngine.XR.ARFoundation
Assembly: solution.dll
Syntax
[DisallowMultipleComponent]
[HelpURL("https://docs.unity3d.com/Packages/com.unity.xr.arfoundation@4.2/api/UnityEngine.XR.ARFoundation.ARSessionOrigin.html")]
public class ARSessionOrigin : MonoBehaviour
Remarks

Session space vs. Unity space

Because an AR device will be used to drive the Camera's position and rotation, you cannot directly place the Camera at an arbitrary position in the Unity scene. Instead, you should position the ARSessionOrigin. This makes the Camera (and any detected features) relative to that as a result.

It is important to keep the Camera and detected features in the same space relative to each other (otherwise, detected features like planes won't appear in the correct place relative to the Camera). The space relative to the AR device's starting position is called "session space" or "device space". For example, when the AR session begins, the device might report its position as (0, 0, 0). Detected features, such as planes, will be reported relative to this starting position. The purpose of the ARSessionOrigin is to convert the session space to Unity world space.

To facilitate this, the ARSessionOrigin creates a new GameObject called "Trackables" as a sibling of its Camera. This should be the parent GameObject for all detected features.

At runtime, a typical scene graph might look like this:

  • AR Session Origin
    • Camera
    • Trackables
      • Detected plane 1
      • Detected plane 2
      • Point cloud
      • etc...

You can access the "trackables" GameObject with trackablesParent.

Note that the localPosition and localRotation of detected trackables remain in real-world meters relative to the AR device's starting position and rotation.

Scale

If you want to scale the content rendered by the ARSessionOrigin you should apply the scale to the ARSessionOrigin's transform. This is preferrable to scaling the content directly, which can have undesirable side effects. Physics and NavMeshes, for example, do not perform well when scaled very small.

Properties

Name Description
camera

The Camera to associate with the AR device. It must be a child of this ARSessionOrigin.
trackablesParent

The parent Transform for all "trackables" (for example, planes and feature points).

Methods

Name Description
MakeContentAppearAt(Transform, Quaternion)

Makes content appear to have orientation rotation relative to the Camera.
MakeContentAppearAt(Transform, Vector3)

Makes content appear to be placed at position.
MakeContentAppearAt(Transform, Vector3, Quaternion)

Makes content appear to be placed at position with orientation rotation.

Events

Name Description
trackablesParentTransformChanged

Invoked during Application.onBeforeRender whenever the trackablesParent transform changes.