RealityKit / Reality Composer中的层次结构

我认为这是一个“理论”问题，而不是实际问题。首先，我应该说编辑Experience包含锚点和实体场景的文件不是一个好主意。

在RealityKit和Reality Composer中，如果您在默认场景中创建了单个对象，则存在相当明确的层次结构：

Scene –> AnchorEntity -> ModelEntity 
                              |
                           Physics
                              |
                          Animation
                              |
                            Audio
                          

如果在场景中放置了两个3D模型，则它们共享相同的锚点：

Scene –> AnchorEntity – – – -> – – – – – – – – ->
                             |                  |
                       ModelEntity01      ModelEntity02
                             |                  |
                          Physics            Physics
                             |                  |
                         Animation          Animation
                             |                  |
                           Audio              Audio

AnchorEntity在RealityKit中定义了World Trackingconfig的哪些属性正在当前中运行ARSession：horizontal/vertical平面检测和/或image detection和/或body detection等。

让我们看一下这些参数：

AnchorEntity(.plane(.horizontal, classification: .floor, minimumBounds: [1, 1]))

AnchorEntity(.plane(.vertical, classification: .wall, minimumBounds: [0.5, 0.5]))

AnchorEntity(.image(group: "Group", name: "model"))

结合来自Reality Composer的两个场景

在本文中，我准备了Reality Composer中的两个场景-第一个场景（ConeAndBox）具有水平平面检测功能，第二个场景（Sphere）具有垂直平面检测功能。如果将RealityKit中的这些场景组合成一个更大的场景，则将获得两种类型的平面检测-水平和垂直。

在此场景中，将两个圆锥体和盒子固定到一个锚点。

在RealityKit中，我可以将这些场景组合为一个场景。

// Plane Detection with a Horizontal anchor
let coneAndBoxAnchor = try! Experience.loadConeAndBox()
coneAndBoxAnchor.children[0].anchor?.scale = [7, 7, 7]
coneAndBoxAnchor.goldenCone!.position.y = -0.1  //.children[0].children[0].children[0]
arView.scene.anchors.append(coneAndBoxAnchor)

coneAndBoxAnchor.name = "mySCENE"
coneAndBoxAnchor.children[0].name = "myANCHOR"
coneAndBoxAnchor.children[0].children[0].name = "myENTITIES"

print(coneAndBoxAnchor)
     
// Plane Detection with a Vertical anchor
let sphereAnchor = try! Experience.loadSphere()
sphereAnchor.steelSphere!.scale = [7, 7, 7]
arView.scene.anchors.append(sphereAnchor)

print(sphereAnchor)

在Xcode的控制台中，您可以看到ConeAndBox具有RealityKit中给定名称的场景层次：

And you can see Sphere scene hierarchy with no names given:

And it's important to note that our combined scene now contains two scenes in an array. Use the following command to print this array:

print(arView.scene.anchors)

It prints:

[ 'mySCENE' : ConeAndBox, '' : Sphere ]

You can reassign a type of tracking via AnchoringComponent (instead of plane detection you can assign an image detection):

coneAndBoxAnchor.children[0].anchor!.anchoring = AnchoringComponent(.image(group: "AR Resources", 
                                                                            name: "planets"))

Retrieving entities and connecting them to new AnchorEntity

For decomposing/reassembling an hierarchical structure of your scene, you need to retrieve all entities and pin them to a single anchor. Take into consideration – tracking one anchor is less intensive task than tracking several ones. And one anchor is much more stable – in terms of the relative positions of scene models – than, for instance, 20 anchors.

let coneEntity = coneAndBoxAnchor.goldenCone!
coneEntity.position.x = -0.2
    
let boxEntity = coneAndBoxAnchor.plasticBox!
boxEntity.position.x = 0.01
    
let sphereEntity = sphereAnchor.steelSphere!
sphereEntity.position.x = 0.2
    
let anchor = AnchorEntity(.image(group: "AR Resources", name: "planets")
anchor.addChild(coneEntity)
anchor.addChild(boxEntity)
anchor.addChild(sphereEntity)
    
arView.scene.anchors.append(anchor)

Useful links

现在，您对如何构造场景以及从这些场景检索实体有了更深入的了解。如果需要其他示例，请参见THIS POST和THIS POST。

聚苯乙烯

显示如何从上载场景的附加代码ExperienceX.rcproject：

import ARKit
import RealityKit

class ViewController: UIViewController {
    
    @IBOutlet var arView: ARView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
                    
        // RC generated "loadGround()" method automatically
        let groundArrowAnchor = try! ExperienceX.loadGround()
        groundArrowAnchor.arrowFloor!.scale = [2,2,2]
        arView.scene.anchors.append(groundArrowAnchor)

        print(groundArrowAnchor)
    }
}