How to detect vertical planes in ARKit?

Detecting vertical planes in ARKit requires utilizing ARKit's plane detection capabilities. The specific steps are as follows:

1. Configure ARSession: First, configure the ARSession and enable vertical plane detection. This is typically achieved by setting the planeDetection property of ARWorldTrackingConfiguration.

swift
let configuration = ARWorldTrackingConfiguration()
configuration.planeDetection = [.vertical] // Enable vertical plane detection
session.run(configuration, options: [])

In the above code, we set the planeDetection property to [.vertical] to enable vertical plane detection.

1. Implement ARSCNViewDelegate: Implement the ARKit scene delegate methods to handle detected planes. The relevant delegate methods include:

swift
func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
    guard let planeAnchor = anchor as? ARPlaneAnchor, planeAnchor.alignment == .vertical else { return }

    // Create a scene node to represent the plane
    let planeNode = createPlaneNode(anchor: planeAnchor)
    node.addChildNode(planeNode)
}

func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
    guard let planeAnchor = anchor as? ARPlaneAnchor, planeAnchor.alignment == .vertical else { return }

    // Update the plane node
    updatePlaneNode(node: node, anchor: planeAnchor)
}

func renderer(_ renderer: SCNSceneRenderer, didRemove node: SCNNode, for anchor: ARAnchor) {
    guard let planeAnchor = anchor as? ARPlaneAnchor, planeAnchor.alignment == .vertical else { return }

    // Remove the plane node
    node.removeFromParentNode()
}

In these methods, we check the alignment property of ARPlaneAnchor to determine if it is a vertical plane. Then, we perform the corresponding node additions, updates, or removals.

1. Create and Update Nodes: Creating and updating nodes is used to visualize detected vertical planes in the AR scene. Typically, a simple geometric shape (such as a plane) is employed.

swift
func createPlaneNode(anchor: ARPlaneAnchor) -> SCNNode {
    let plane = SCNPlane(width: CGFloat(anchor.extent.x), height: CGFloat(anchor.extent.z))
    plane.firstMaterial?.diffuse.contents = UIColor.red.withAlphaComponent(0.5) // Semi-transparent red

    let planeNode = SCNNode(geometry: plane)
    planeNode.eulerAngles.x = -.pi / 2 // Rotate the plane to display vertically
    return planeNode
}

func updatePlaneNode(node: SCNNode, anchor: ARPlaneAnchor) {
    if let plane = node.geometry as? SCNPlane {
        plane.width = CGFloat(anchor.extent.x)
        plane.height = CGFloat(anchor.extent.z)
        node.position = SCNVector3(anchor.center.x, 0, anchor.center.z)
    }
}

By following these steps, you can effectively detect and handle vertical planes in ARKit. This capability is highly useful in many AR applications, such as furniture placement and interior design, where interaction with vertical surfaces is necessary.