swift - Reality Composer 默认锚点

Question

当您使用 Reality Composer 创建任何场景时，您必须首先选择哪种类型的锚点“地板、墙壁、面、对象”，这意味着当您加载场景时，它会自动将其放置到指定的锚点。

我的问题是，有什么方法可以从代码中手动设置它，以便我例如进行命中测试，然后手动将其锚定到特定点？

谢谢。

Answer 1

官方文档没有提及能够在运行时更改默认锚点，但从您的描述看来，您可以Select Object Anchoring to Place a Scene Near Detected Objects按照此处所述尝试： https ://developer.apple.com/documentation/realitykit/creating_3d_content_with_reality_composer/selecting_an_anchor_for_a_reality_composer_scene

Answer 2

您可以使用以下代码轻松应用其他类型的锚（在实现命中测试或光线投射时）（Reality Composer 中的默认锚是.horizontal）：

import ARKit
import RealityKit

@IBAction func onTap(_ sender: UITapGestureRecognizer) {

    let estimatedPlane: ARRaycastQuery.Target = .estimatedPlane              
    let alignment: ARRaycastQuery.TargetAlignment = .vertical           
    let tapLocation: CGPoint = sender.location(in: arView)

    let result: [ARRaycastResult] = arView.raycast(from: tapLocation,
                                               allowing: estimatedPlane,
                                              alignment: alignment)

    guard let rayCast: ARRaycastResult = result.first
    else { return }

    let anchor = AnchorEntity(world: rayCast.worldTransform)
    anchor.addChild(myScene)
    arView.scene.anchors.append(anchor)
}

或者您可以自动放置锚点（例如，ARFaceAnchor对于检测到的人脸）：

extension ViewController: ARSessionDelegate {

    func session(_ session: ARSession,didUpdate anchors: [ARAnchor]) {

        guard let faceAnchor = anchors.first as? ARFaceAnchor
        else { return }

        let anchor = AnchorEntity(anchor: faceAnchor)

        // RealityKit's Facial analog
        // AnchorEntity(.face).self

        anchor.addChild(glassModel)        
        arView.scene.anchors.append(anchor)
    }
}

...或者您可以ARImageAnchor以相同的方式放置：

extension ViewController: ARSessionDelegate {

    func session(_ session: ARSession, didUpdate anchors: [ARAnchor]) {

         guard let imageAnchor = anchors.first as? ARImageAnchor,
               let _ = imageAnchor.referenceImage.name
         else { return }

        let anchor = AnchorEntity(anchor: imageAnchor)

        // RealityKit's image anchor analog
        // AnchorEntity(.image(group: "Group", name: "model")).self

        anchor.addChild(imageModel)        
        arView.scene.anchors.append(anchor)
    }
}