ios - 使用 ARKit 2 检测对象时显示边界框

可以显示boundingBox关于ARReferenceObject它被检测到的先验；尽管我不确定您为什么要这样做（无论如何都要提前）。

例如，假设您的 referenceObject 在水平面上，您首先需要将估计的边界框放置在平面上（或使用其他方法提前放置），并在检测 ARPlaneAnchor 并放置boundingBox 很可能您的模型已经被检测到。

可能的方法：

毫无疑问，您知道ARReferenceObject一个center,extent和scale属性以及一组rawFeaturePoints与对象关联的。

因此，我们可以根据 Apple 在Scanning & Detecting 3D Objects中的一些示例代码创建自己的 boundingBox 节点，并创建我们自己的 SCNNode 它将显示一个近似大小的边界框，该边界框在ARReferenceObject被检测到之前存储在本地.

请注意，您需要从 Apple 示例代码中找到“wireframe_shader”，以使 boundingBox 呈现透明：

import Foundation
import ARKit
import SceneKit

class BlackMirrorzBoundingBox: SCNNode {

    //-----------------------
    // MARK: - Initialization
    //-----------------------

    /// Creates A WireFrame Bounding Box From The Data Retrieved From The ARReferenceObject
    ///
    /// - Parameters:
    ///   - points: [float3]
    ///   - scale: CGFloat
    ///   - color: UIColor
    init(points: [float3], scale: CGFloat, color: UIColor = .cyan) {
        super.init()

        var localMin = float3(Float.greatestFiniteMagnitude)
        var localMax = float3(-Float.greatestFiniteMagnitude)

        for point in points {
            localMin = min(localMin, point)
            localMax = max(localMax, point)
        }

        self.simdPosition += (localMax + localMin) / 2
        let extent = localMax - localMin

        let wireFrame = SCNNode()
        let box = SCNBox(width: CGFloat(extent.x), height: CGFloat(extent.y), length: CGFloat(extent.z), chamferRadius: 0)
        box.firstMaterial?.diffuse.contents = color
        box.firstMaterial?.isDoubleSided = true
        wireFrame.geometry = box
        setupShaderOnGeometry(box)
        self.addChildNode(wireFrame)
    }

    required init?(coder aDecoder: NSCoder) { fatalError("init(coder:) Has Not Been Implemented") }

    //----------------
    // MARK: - Shaders
    //----------------

    /// Sets A Shader To Render The Cube As A Wireframe
    ///
    /// - Parameter geometry: SCNBox
    func setupShaderOnGeometry(_ geometry: SCNBox) {
        guard let path = Bundle.main.path(forResource: "wireframe_shader", ofType: "metal", inDirectory: "art.scnassets"),
            let shader = try? String(contentsOfFile: path, encoding: .utf8) else {

                return
        }

        geometry.firstMaterial?.shaderModifiers = [.surface: shader]
    }

}

要显示边界框，您将执行以下操作，注意在我的示例中，我有以下变量：

 @IBOutlet var augmentedRealityView: ARSCNView!
 let configuration = ARWorldTrackingConfiguration()
 let augmentedRealitySession = ARSession()

要在检测到实际对象本身之前显示 boundingBox，您可以调用func loadBoundigBox例如viewDidLoad：

/// Creates A Bounding Box From The Data Available From The ARObject In The Local Bundle
func loadBoundingBox(){

    //1. Run Our Session
    augmentedRealityView.session = augmentedRealitySession
    augmentedRealityView.delegate = self

    //2. Load A Single ARReferenceObject From The Main Bundle
    if let objectURL =  Bundle.main.url(forResource: "fox", withExtension: ".arobject"){

        do{
            var referenceObjects = [ARReferenceObject]()
            let object = try ARReferenceObject(archiveURL: objectURL)

            //3. Log it's Properties
            print("""
                Object Center = \(object.center)
                Object Extent = \(object.extent)
                Object Scale = \(object.scale)
                """)

            //4. Get It's Scale
            let scale = CGFloat(object.scale.x)

            //5. Create A Bounding Box
            let boundingBoxNode = BlackMirrorzBoundingBox(points: object.rawFeaturePoints.points, scale: scale)

            //6. Add It To The ARSCNView
            self.augmentedRealityView.scene.rootNode.addChildNode(boundingBoxNode)

            //7. Position It 0.5m Away From The Camera
            boundingBoxNode.position = SCNVector3(0, -0.5, -0.5)

            //8. Add It To The Configuration
            referenceObjects.append(object)
            configuration.detectionObjects = Set(referenceObjects)

        }catch{
            print(error)
        }

    }

    //9. Run The Session
    augmentedRealitySession.run(configuration, options: [.resetTracking, .removeExistingAnchors])
    augmentedRealityView.automaticallyUpdatesLighting = true
}

上面的示例简单地从未检测到的边界框创建了一个边界ARReferenceObject框，并将其放置在距边界 0.5 米和距边界 0.5 米的位置，Camera从而产生如下内容：

当然，您最初需要处理 boundBox 的位置，以及处理 boundingBox 'indicator' 的移除。

下面的方法只是在检测到实际对象时显示一个boundBox，例如：

//--------------------------
// MARK: - ARSCNViewDelegate
//--------------------------

extension ViewController: ARSCNViewDelegate{

    func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {

        //1. Check We Have A Valid ARObject Anchor 
        guard let objectAnchor = anchor as? ARObjectAnchor else { return }

        //2. Create A Bounding Box Around Our Object
        let scale = CGFloat(objectAnchor.referenceObject.scale.x)
        let boundingBoxNode = BlackMirrorzBoundingBox(points: objectAnchor.referenceObject.rawFeaturePoints.points, scale: scale)
        node.addChildNode(boundingBoxNode)

    }

}

这会产生这样的结果：

关于检测计时器，Apple 示例代码中有一个示例，显示了检测模型所需的时间。

以最原始的形式（不考虑毫秒），您可以执行以下操作：

首先创建 ATimer和 avar来存储检测时间，例如：

var detectionTimer = Timer()

var detectionTime: Int = 0

然后，当您运行ARSessionConfiguration初始化计时器时，例如：

/// Starts The Detection Timer
func startDetectionTimer(){

     detectionTimer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(logDetectionTime), userInfo: nil, repeats: true)
}

/// Increments The Total Detection Time Before The ARReference Object Is Detected
@objc func logDetectionTime(){
    detectionTime += 1

}

然后，当ARReferenceObject检测到使计时器无效并记录时间时，例如：

//--------------------------
// MARK: - ARSCNViewDelegate
//--------------------------

extension ViewController: ARSCNViewDelegate{

    func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {

        //1. Check We Have A Valid ARObject Anchor
        guard let _ = anchor as? ARObjectAnchor else { return }

        //2. Stop The Timer
        detectionTimer.invalidate()

        //3. Log The Detection Time
        print("Total Detection Time = \(detectionTime) Seconds")

        //4. Reset The Detection Time
        detectionTime = 0

    }

}

这应该足以让你开始......

请注意，此示例在扫描对象时不提供边界框（请查看 Apple 示例代码），它提供了基于您的问题中隐含的现有 ARReferenceObject 的边界框（假设我解释正确）。

ios - 使用 ARKit 2 检测对象时显示边界框

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