In ARKit, what are the plane detection delegate methods in ARSKViewDelegate? - ios

Question

Reading the documentation for planeDetection, it states
If you enable horizontal plane detection, the session adds ARPlaneAnchor objects and notifies your ARSessionDelegate, ARSCNViewDelegate, or ARSKViewDelegate object whenever its analysis of captured video images detects an area that appears to be a flat surface.
However, I can't find the method in ARSKViewDelegate that would receive the plane detection events. I see plenty of examples with ARSCNViewDelegate. Would it be in the method view(_:didAdd:for:) and if so how can I detect whether it's a plane detection anchor?

Answer 1

Detected planes are anchors added to the ARSession, so you use the delegate methods for responding to newly added anchors.
In Apple's "Providing 2D Virtual Content with SpriteKit" doc, they show some basic code for creating SpriteKit nodes in response to new anchors:
func view(_ view: ARSKView, nodeFor anchor: ARAnchor) -> SKNode? {
return SKLabelNode(text: "👾")
}
If you want to put a billboarded emoji at the center of every detected plane, that's all the code you need. Otherwise, you can do one or more of the following...
Provide a different SpriteKit node — initialize it in that method and return it there. (Refer to SpriteKit docs, tutorials, SO questions, etc on how to use SpriteKit.)
Also be adding anchors to the scene manually, in which case you might need to sort out the plane-detection-based anchors from the rest. Plane anchors are ARPlaneAnchor instances, so you can test types in that method:
func view(_ view: ARSKView, nodeFor anchor: ARAnchor) -> SKNode? {
if let plane = anchor as? ARPlaneAnchor {
// this anchor came from plane detection
return SKLabelNode(text: "✈️") // or whatever other SK content
} else {
// this anchor came from manually calling addAnchor on the ARSession
return SKLabelNode(text: "⚓️") // or whatever other SK content
}
}
Use some of the properties of ARPlaneAnchor to choose what SK content to provide or how to set it up. In that case, use the conditional cast (as? ARPlaneAnchor) like above so you can access those properties.
Change the position/orientation of your SK content relative to that provided/managed by ARKit, or add multiple SK nodes for each anchor. In that case, implement view(_:didAdd:for:) instead, create new node(s) for your SK content and set their positions (etc) before adding them as children of the node that method provides.