ARKit limit display distance of a node - swift

Question

I would like to create a node in sceneView, that is displayed at normal position in the scene, until user get too close or too far from it. Then it should be displayed at the same direction from the user, but with restricted distance. So far best I found is SCNDistanceConstraint, which limits this distance, but the problem is, that this constraint after it moved the node, this node stays in this new place. So for example, I want to limit the node to be displayed not closer then one meter from camera. I'm getting closer to the node, and it's being pushed away, but then when I get camera back, this node should return to it's original position - for now it stays where it was pushed. Is there some easy way to get such behavior?

Answer 1

Im not entirely sure I have understood what you mean, but it seems you always want your SCNNode to be positioned 1m away from the camera, but keeping its other x, y values?
If this is the case then you can do something like this:
func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
//1. Get The Current Node On Screen & The Camera Point Of View
guard let nodeToPosition = currentNode, let pointOfView = augmentedRealityView.pointOfView else { return }
//2. Set The Position Of The Node 1m Away From The Camera
nodeToPosition.simdPosition.z = pointOfView.presentation.worldPosition.z - 1
//3. Get The Current Distance Between The SCNNode & The Camera
let positionOfNode = SCNVector3ToGLKVector3(nodeToPosition.presentation.worldPosition)
let positionOfCamera = SCNVector3ToGLKVector3(pointOfView.presentation.worldPosition)
let distanceBetweenNodeAndCamera = GLKVector3Distance(positionOfNode, positionOfCamera)
print(distanceBetweenNodeAndCamera)
}
I have added in part three, so you could use the distance to do some additional calculations etc.
Hope this points you in the right direction...

Answer 2

The answer above is not exactly what I need - I want object to be displayed like it was just placed in normal position, so I can get closer and farer to/from it, but limit how close/far I can get from that object. When I'm beyond that limit, object should start move to be always within given distance range from camera. Anyway I think I have found some right direction in this. Instead of assigning position, I'm creating a constraint that constantly updates position of my node to be either in given position if it's in given range from user, or if not, adjusts this position to fit in that range:
private func setupConstraint() {
guard let mainNodeDisplayDistanceRange = mainNodeDisplayDistanceRange else {
constraints = nil
position = requestedPosition
return
}
let constraint = SCNTransformConstraint.positionConstraint(inWorldSpace: true) { (node, currentPosition) -> SCNVector3 in
var cameraPositionHorizontally = (self.augmentedRealityView as! AugmentedRealityViewARKit).currentCameraPosition
cameraPositionHorizontally.y = self.requestedPosition.y
let cameraToObjectVector = self.requestedPosition - cameraPositionHorizontally
let horizontalDistanceFromCamera = Double((cameraToObjectVector).distanceHorizontal)
guard mainNodeDisplayDistanceRange ~= horizontalDistanceFromCamera else {
let normalizedDistance = horizontalDistanceFromCamera.keepInRange(mainNodeDisplayDistanceRange)
let normalizedPosition = cameraPositionHorizontally + cameraToObjectVector.normalizeHorizontally(toDistance: normalizedDistance)
return normalizedPosition
}
return self.requestedPosition
}
constraints = [constraint]
}
internal var requestedPosition: SCNVector3 = .zero {
didSet {
setupConstraint()
}
}
This starts to work fine, but I still need to find a way to animate this.