Displaying an "ARAnchor" in ARSCNView - swift

Question

In ARKit we can visualise Feature Points' Cloud detected in a ARSession via .showFeaturePoints Type Property:
self.sceneView.debugOptions = [ARSCNDebugOptions.showFeaturePoints]
Also, we can display a coordinate axis visualization indicating the position and orientation of the AR World Coordinate System:
static let showWorldOrigin: SCNDebugOptions
But is it possible to show ARAnchors in ARSCNView?
And if yes, how could we do it?

Answer 1

Just to follow up on #sj-r and #Rickster's comments.
The example code that #Rickster was talking about in regard to the coordinateOrigin.scn is found here: Creating Face Based Experiences
And here is a little snippet I have used before to visualize Axis:
class BMOriginVisualizer: SCNNode {
//----------------------
//MARK: - Initialization
//---------------------
/// Creates An AxisNode To Vizualize ARAnchors
///
/// - Parameter scale: CGFloat
init(scale: CGFloat = 1) {
super.init()
//1. Create The X Axis
let xNode = SCNNode()
let xNodeGeometry = SCNBox(width: 1, height: 0.01, length: 0.01, chamferRadius: 0)
xNode.geometry = xNodeGeometry
xNodeGeometry.firstMaterial?.diffuse.contents = UIColor.red
xNode.position = SCNVector3(0.5, 0, 0)
self.addChildNode(xNode)
//2. Create The Y Axis
let yNode = SCNNode()
let yNodeGeometry = SCNBox(width: 0.01, height: 1, length: 0.01, chamferRadius: 0)
yNode.geometry = yNodeGeometry
yNode.position = SCNVector3(0, 0.5, 0)
yNodeGeometry.firstMaterial?.diffuse.contents = UIColor.green
self.addChildNode(yNode)
//3. Create The Z Axis
let zNode = SCNNode()
let zNodeGeometry = SCNBox(width: 0.01, height: 0.01, length: 1, chamferRadius: 0)
zNode.geometry = zNodeGeometry
zNodeGeometry.firstMaterial?.diffuse.contents = UIColor.blue
zNode.position = SCNVector3(0, 0, 0.5)
self.addChildNode(zNode)
//4. Scale Our Axis
self.scale = SCNVector3(scale, scale, scale)
}
required init?(coder aDecoder: NSCoder) { fatalError("Vizualizer Coder Not Implemented") }
}
Which can be initialised like so:
func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
let anchorVizualizer = BMOriginVisualizer(scale: 0.5)
node.addChildNode(anchorVizualizer)
}
Hopefully this will provide useful as an expansion to the answer provided by #sj-r.

Answer 2

ARAnchor only represents 'position and orientation'. Things you can see are SCNNodes.
You can attach a node for each anchor you add via a method in ARSCNViewDelegate
func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {
//create a node so you can visualize the location.
let sphereNode = SCNNode(geometry: SCNSphere(radius: 0.5))
sphereNode.geometry?.firstMaterial?.diffuse.contents = UIColor.blue
return sphereNode
}
This is called after you add an anchor (or when the system adds anchors such as when you have plane detection or image/object detection turned on)
sceneView.session.add(anchor:)