Realitykit - Stored Entities & Load The Scene Aynchronously from The Url

RealityKit – Asynchronous model loading doesn't work

Use the following macOS code version to find out how to load model asynchronously:

import AppKit
import RealityKit
import Combine

class GameViewController: NSViewController {
    
    @IBOutlet var arView: ARView!
    var model: ModelEntity? = nil
    let anchor = AnchorEntity()
    var cancellable: AnyCancellable? = nil
    
    override func awakeFromNib() {
    
        arView.environment.background = .color(.systemTeal)
                
        cancellable = Entity.loadModelAsync(named: "Glasses.usdz")
            .sink(receiveCompletion: { completion in
                if case let .failure(error) = completion {
                    print("Unable to load a model due to error \(error)")
                }
                self.cancellable?.cancel()
                
            }, receiveValue: { [self] (model: Entity) in
                if let model = model as? ModelEntity {
                    self.model = model
                    cancellable?.cancel()
                    print("Congrats! Model is successfully loaded!")
                    anchor.addChild(model)
                    anchor.position = [0.4, 1.5, -1]
                    anchor.scale = [300, 300, 300]   // set appropriate scale
                    arView.scene.anchors.append(anchor)
                }
            })
    }
}

Loading anchor from url async doesnt work

You have to store subscriber somewhere in member

// somewhere above
private var subscribers: Set<AnyCancellable>()

...
if let url = url {
    let loadRequest = Entity.loadAnchorAsync(contentsOf: url)
    loadRequest.sink(receiveCompletion: { completion in
        // handle completion
    }, receiveValue: { anchor in
        self.arView.scene.addAnchor(anchor)
    }).store(in: &self.subscribers) // << keep it alive
} else {
        fatalError("no url")
}

Error in displaying reality file from network

Uploading a .reality model from web works fine. You can easily check this in Xcode Simulator:

import UIKit
import RealityKit

class ViewController: UIViewController {
    
    @IBOutlet var arView: ARView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let url = URL(string: "https://developer.apple.com/augmented-reality/quick-look/models/cosmonaut/CosmonautSuit_en.reality")
        let documents = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
        let destination = documents.appendingPathComponent(url!.lastPathComponent)
        let session = URLSession(configuration: .default,
                                      delegate: nil,
                                 delegateQueue: nil)
        
        var request = URLRequest(url: url!)
        request.httpMethod = "GET"
        
        let downloadTask = session.downloadTask(with: request, completionHandler: { (location: URL?,
                                  response: URLResponse?,
                                     error: Error?) -> Void in
            
            let fileManager = FileManager.default
                
            if fileManager.fileExists(atPath: destination.path) {
                try! fileManager.removeItem(atPath: destination.path)
            }
            try! fileManager.moveItem(atPath: location!.path,
                                      toPath: destination.path)
                
            DispatchQueue.main.async {
                do {
                    let model = try Entity.loadAnchor(contentsOf: destination)
                    self.arView.scene.addAnchor(model)
                } catch {
                    print("Fail loading entity.")
                }
            }
        })
        downloadTask.resume()
    }
}

RealityKit – How to add motion to a loaded ModelEntity from USDZ file?

Add to your code .generateCollisionShapes(recursive:) instance method for every participant (entity) that not only creates collision's shapes but also allows you to simulate physics.

import SwiftUI
import RealityKit

struct ARViewContainer: UIViewRepresentable {
    
    let boxx = ModelEntity(mesh: .generateBox(size: 0.5))
    let ball = ModelEntity(mesh: .generateSphere(radius: 0.25))
    let anchor = AnchorEntity()
    
    func makeUIView(context: Context) -> ARView {
        let arView = ARView(frame: .zero)
        // BALL
        ball.physicsBody = .init()
        ball.physicsMotion = .init()
        ball.physicsMotion?.linearVelocity = [10,0,0]
        ball.position.x = -3
        ball.generateCollisionShapes(recursive: true)
        anchor.addChild(ball)
        // BOX
        boxx.physicsBody = .init()
        boxx.physicsMotion = .init()
        boxx.physicsMotion?.linearVelocity = [0,2,0]
        boxx.generateCollisionShapes(recursive: true)
        anchor.addChild(boxx)
        // Anchor
        anchor.position.z = -3
        arView.scene.addAnchor(anchor)
        return arView
    }
    func updateUIView(_ uiView: ARView, context: Context) { }
}

...

struct ContentView : View {
    var body: some View {
        return ARViewContainer().edgesIgnoringSafeArea(.all)
    }
}

For more details, read THIS post.

Available animations collection is empty, while using .loadModelAsync()

Use ModelEntity.loadAsync. It loads full hierarchy including animation.

import RealityKit
import Combine

let anchor = AnchorEntity()
var cancellable: AnyCancellable? = nil

self.cancellable = ModelEntity.loadAsync(named: "biplane.usdz").sink(
        
    receiveCompletion: { completion in

        if case let .failure(error) = completion {
            print("Unable to load a model \(error)")
        }
        self.cancellable?.cancel()
    }, 

    receiveValue: { [self] planeModel in

        let animation = planeModel.availableAnimations[0]
            
        anchor.addChild(planeModel)
        anchor.position = [0, 0,-2]
        anchor.scale = [0.1, 0.1, 0.1]
        arView.scene.anchors.append(anchor)
                
        planeModel.playAnimation(animation.repeat(count: .max))
    }
)

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