Getting rotation of ARAnchor from didAdd anchors - scenekit

Question

So I am using session(_ session: ARSession, didAdd anchors: [ARAnchor] to get all detected planes (I cannot use renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) Because I am using RealityKit instead of ARKit).
So my question is, How can I get the rotation of the detected anchor from this method? I want to create a plane Entity that has exactly the same position, size, orientation & rotation of the detected anchor. So far Im using the extent for the size, center for position but I can't figure out how to get the rotation. Because right now Its detected correctly (Right position and size)but with wrong rotation that the real plane.

Answer 1

You can get the position and orientation of the ARPlaneAnchor from its transform property, then use that to render the bounding plane in RealityKit.
extension float4x4 {
/// Returns the translation components of the matrix
func toTranslation() -> SIMD3<Float> {
return [self[3,0], self[3,1], self[3,2]]
}
/// Returns a quaternion representing the
/// rotation component of the matrix
func toQuaternion() -> simd_quatf {
return simd_quatf(self)
}
}
func session(_ session: ARSession, didUpdate anchors: [ARAnchor]) {
guard let planeAnchor = anchors[0] as? ARPlaneAnchor else {
return
}
// NOTE: When the ARPlaneAnchor is first created its transform
// contains the position and the plane.center == [0,0,0]. On updates
// the plane.center will change as the extents of the plane change.
let position = planeAnchor.transform.toTranslation()
let orientation = planeAnchor.transform.toQuaternion()
// The center is a position before the orientation is taken in to
// account, so we need to rotate it to get the true position before
// we add it to the anchors position
let rotatedCenter = orientation.act(planeAnchor.center)
// You have a ModelEntity that you created earlier
// e.g. modelEntity
// Assuming you added the entity to an anchor that is just
// fixed at 0,0,0 in the world, or you created a custom entity
// with HasAnchor set to 0,0,0
modelEntity.transform.translation = position + rotatedCenter
modelEntity.transform.rotation = orientation
// Doesn't seem to be a way to update meshes in RealityKit so
// just create a new plane mesh for the updated dimensions
modelEntity.model?.mesh = MeshResource.generatePlane(
width: planeAnchor.extent.x,
depth: planeAnchor.extent.z
)
}