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

问题描述

我想要实现的目标: 将球体附加到相机位置(以便在设备移动时它始终保持在屏幕的中心)并检测它何时位于其他 AR 之上对象 - 在 AR 对象上触发其他动作/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附加到屏幕的中心，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

但是我通过这种方法不断得到地平面作为结果.是否有我遗漏的东西或有不同的方法来实现这一点

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:为了防止出现问题，我创建了我的基本场景，因为我想跟踪图像并在 Reality Composer 中的图像标记顶部添加内容并使用 .rcprojectXcode 还为所有重叠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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