SCNNode is not being anchored at real world coordinates

Question

I have a simple SCNNode that I want to place in the real-world position, the node corresponds to a landmark with known coordinates. I want to keep the SCNNode still at its location, however it tends to move with the camera. I cannot use plane detection or a hit-test to place the node in the real-world, I can only use the real-world coordinates. My current solution creates an ARanchor using the SCNNodes world transform.

showNode(node: Node, location: convertedPoint)
let anchor = ARAnchor(transform: Node.simdWorldTransform)
self.sceneView.session.add(anchor: anchor)

I thought this would be enough to anchor the node. Is there a solution to anchor the node without using plane detection or a hit-test?

Thanks

jfriesenhahn jfriesenhahn · Accepted Answer · 2020-02-19T01:26:54

First, even if you stabilize your node with an anchor, it's never going to be perfect, just better.

However, while an ARAnchor is being created at the coordinates you are telling it, but the node you want to be stabilized is not actually being placed within that anchor.

You need to implement the renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) function in your ARSCNViewDelegate and return the target node you want to be stabilized by the anchor (Alternatively, you can add your node as a childNode of the default created anchor node by implementing the renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) function).

If your nodeToBeStabilized object is available as property within the ViewController, then a very dumb implementation might be something like this:

extension WAViewController: ARSCNViewDelegate, ARSessionDelegate {
    func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {
        return nodeToBeStabilized
    }
}

SCNNode is not being anchored at real world coordinates

1 Answers