Reality Composer default Anchor - swift

Question

When you create any scene with Reality Composer, you have to choose first what type of anchor "floor, wall, face, object" this mean when you load the scene it automatically places it self to the specified anchor.
My question is, Is there is any way to set it manually from code so that I would for example do a hit test and then anchor it to a specific point manually?
Thanks.

Answer 1

The official documentation has no reference to being able to change the default Anchor at runtime but from your description it sounds like you could try Select Object Anchoring to Place a Scene Near Detected Objects as described here:
https://developer.apple.com/documentation/realitykit/creating_3d_content_with_reality_composer/selecting_an_anchor_for_a_reality_composer_scene

Answer 2

You can easily apply other type of anchor (when implementing hit-testing or ray-casting) using the following code (default anchor in Reality Composer is .horizontal):
import ARKit
import RealityKit
#IBAction func onTap(_ sender: UITapGestureRecognizer) {
let estimatedPlane: ARRaycastQuery.Target = .estimatedPlane
let alignment: ARRaycastQuery.TargetAlignment = .vertical
let tapLocation: CGPoint = sender.location(in: arView)
let result: [ARRaycastResult] = arView.raycast(from: tapLocation,
allowing: estimatedPlane,
alignment: alignment)
guard let rayCast: ARRaycastResult = result.first
else { return }
let anchor = AnchorEntity(world: rayCast.worldTransform)
anchor.addChild(myScene)
arView.scene.anchors.append(anchor)
}
Or you can place anchors automatically (for example, like ARFaceAnchor for detected face):
extension ViewController: ARSessionDelegate {
func session(_ session: ARSession,didUpdate anchors: [ARAnchor]) {
guard let faceAnchor = anchors.first as? ARFaceAnchor
else { return }
let anchor = AnchorEntity(anchor: faceAnchor)
// RealityKit's Facial analog
// AnchorEntity(.face).self
anchor.addChild(glassModel)
arView.scene.anchors.append(anchor)
}
}
...or you can place ARImageAnchor the same way:
extension ViewController: ARSessionDelegate {
func session(_ session: ARSession, didUpdate anchors: [ARAnchor]) {
guard let imageAnchor = anchors.first as? ARImageAnchor,
let _ = imageAnchor.referenceImage.name
else { return }
let anchor = AnchorEntity(anchor: imageAnchor)
// RealityKit's image anchor analog
// AnchorEntity(.image(group: "Group", name: "model")).self
anchor.addChild(imageModel)
arView.scene.anchors.append(anchor)
}
}