在RealityKit中实现十字准线行为 [英] Implement a crosshair kind behaviour in RealityKit

问题描述

我要实现的目标:将球体附加到摄像头位置(以便随着设备移动，球体始终位于屏幕中央)并检测其何时位于其他AR顶部对象-触发AR对象上的其他动作/行为.

What I want to achieve: Attach a sphere to the camera position (so that it always stay at the center of the screen as the device move) and detect when it is on top of other AR objects - to trigger other actions/behaviour on the AR objects.

方法:我已经创建了球体，并将其附着到屏幕的中心，如下所示:

Approach: I have created the sphere and attached to the center of the screen as shown below

@IBOutlet var arView: ARView!

override func viewDidLoad() {
    super.viewDidLoad()

    let mesh = MeshResource.generateSphere(radius: 0.1)
    let sphere = ModelEntity(mesh: mesh)

    let anchor = AnchorEntity(.camera)

    sphere.setParent(anchor)
    arView.scene.addAnchor(anchor)

    sphere.transform.translation.z = -0.75
}

下一步，在会话(_:didUpdate:)

Next step, perform a hittest or a raycast in session(_:didUpdate:)

 let results = arView.hitTest(CGPoint(x: 0.5, y: 0.5), query: .all, mask: .default)
//normalised center ; 2D position of the camera (our sphere) in the view’s coordinate system

但是，通过这种方法，我不断获得接地平面.是否有我缺少的东西，或者有其他方法可以实现这一目标

But I am constantly getting ground plane as my result with this approach. Is there something I am missing or there is a different approach to achieving this

注意:以防万一我在跟踪图像并在Reality Composer中的图像标记顶部添加内容并在其中使用.rcproject时创建了基本场景.Xcode还为所有覆盖的项目启用了碰撞属性.

Note: Just in case there is something wrong I have created my basic scene as I want to track an image and add content on top of the image marker in Reality Composer and using the .rcproject in Xcode also have enabled collision property for all the overlaid items.

推荐答案

尝试以下解决方案:

import ARKit
import RealityKit

class ViewController: UIViewController {
    
    @IBOutlet var arView: ARView!
    var sphere: ModelEntity?
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        let touch = arView.center
        let results: [CollisionCastHit] = arView.hitTest(touch)
        
        if let result: CollisionCastHit = results.first {
            if result.entity.name == "Cube" && sphere?.isAnchored == true {
                print("BOOM!")
            }
        }
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Crosshair
        let mesh01 = MeshResource.generateSphere(radius: 0.01)
        sphere = ModelEntity(mesh: mesh01)
        sphere?.transform.translation.z = -0.15
        let cameraAnchor = AnchorEntity(.camera)
        sphere?.setParent(cameraAnchor)
        arView.scene.addAnchor(cameraAnchor)
        
        // Model for collision
        let mesh02 = MeshResource.generateBox(size: 0.3)
        let box = ModelEntity(mesh: mesh02, materials: [SimpleMaterial()])
        box.generateCollisionShapes(recursive: true)
        box.name = "Cube"
        let planeAnchor = AnchorEntity(.plane(.any, 
                              classification: .any, 
                               minimumBounds: [0.2, 0.2]))
        box.setParent(planeAnchor)
        arView.scene.addAnchor(planeAnchor)
    }
}

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