ARKit – Raycasting using a world ray instead of a screen point - swift

Question

I want to achieve something similar like ARCore's raycast method which takes an arbitrary ray in world space coordinates instead of a screen-space point:
List<HitResult> hitTest (float[] origin3, int originOffset, float[] direction3, int directionOffset)
I see ARKit itself has not that method like that, but in any way maybe someone has an idea!
Thanks.

Answer 1

In Apple RealityKit and ARKit frameworks you can find three main types of Raycast methods: ARView Raycast, ARSession Raycast and Scene Raycast (or World Raycast). All methods written in Swift:
ARView.raycast(from:allowing:alignment:)
This instance method performs a ray cast, where a ray is cast into the scene from the center of the camera through a point in the view, and the results are immediately returned. You can use this type of raycast in ARKit.
func raycast(from point: CGPoint,
allowing target: ARRaycastQuery.Target,
alignment: ARRaycastQuery.TargetAlignment) -> [ARRaycastResult]
ARView.scene.raycast(origin:direction:query:mask:relativeTo:)
WORLD RAYCAST
This instance method performs a convex ray cast against all the geometry in the scene for a ray of a given origin, direction, and length.
func raycast(origin: SIMD3<Float>,
direction: SIMD3<Float>,
query: CollisionCastQueryType,
mask: CollisionGroup,
relativeTo: Entity) -> [CollisionCastHit]
ARView.session.trackedRaycast(_:updateHandler:)
This instance method repeats a ray-cast query over time to notify you of updated surfaces in the physical environment. You can use this type of raycast in ARKit 3.5.
func trackedRaycast(_ query: ARRaycastQuery,
updateHandler: #escaping ([ARRaycastResult]) -> Void) -> ARTrackedRaycast?
ARView.trackedRaycast(from:allowing:alignment:updateHandler:)
This RealityKit's instance method also performs a tracked ray cast, but here a ray is cast into the scene from the center of the camera through a point in the view.
func trackedRaycast(from point: CGPoint,
allowing target: ARRaycastQuery.Target,
alignment: ARRaycastQuery.TargetAlignment,
updateHandler: #escaping ([ARRaycastResult]) -> Void) -> ARTrackedRaycast?
Code snippet 01:
import RealityKit
let startPosition: SIMD3<Float> = [3,-2,0]
let endPosition: SIMD3<Float> = [10,7,-5]
let query: CollisionCastQueryType = .all
let mask: CollisionGroup = .all
let raycasts: [CollisionCastHit] = arView.scene.raycast(from: startPosition,
to: endPosition,
query: query,
mask: mask,
relativeTo: nil)
guard let rayCast: CollisionCastHit = raycasts.first
else {
return
}
Code snippet 02:
import ARKit
let query = arView.raycastQuery(from: screenCenter,
allowing: .estimatedPlane,
alignment: .any)
let raycast = session.trackedRaycast(query) { results in
if let result = results.first {
object.transform = result.transform
}
}
raycast.stop()