Importing and animating multiple .usdz objects in RealityKit

Question

I have a simple RealityKit scene that displays a .USDZ cow. I saw a couple answers to these questions, but I wasn't able to implement them into my code:

1. How can I play the animations that are built into this file?
2. How am I able to bring a second object (let's say a horse) into the scene?

Additionally, is there anything I can do to clean up my code/ make it easier to read?

I appreciate any help I can get! Thank you,

import UIKit
import RealityKit
import ARKit

 class WelcomeViewController: UIViewController {

//delay app launch to show splash screen
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        Thread.sleep(forTimeInterval: 3.0)
        // Override point for customization after application launch.
        return true
    }
//end splash screen delay

   @IBAction func gotPressed(_ sender: Any) {
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    if let viewController = storyboard.instantiateViewController(withIdentifier: "ViewController") as? ViewController {
        self.present(viewController, animated: true, completion: nil) /// present the view controller (the one with the ARKit)!
    }    }

 }
 class ViewController: UIViewController {

@IBOutlet var arView: ARView!

override func viewDidLoad() {
    super.viewDidLoad()
    
    overlayCoachingView()
    

}
//Overlay coaching view "adjust iphone scan"
func overlayCoachingView () {
    
    let coachingView = ARCoachingOverlayView(frame: CGRect(x: 0, y: 0, width: arView.frame.width, height: arView.frame.height))
    
    coachingView.session = arView.session
    coachingView.activatesAutomatically = true
    coachingView.goal = .horizontalPlane
    
    view.addSubview(coachingView)
    
}//end overlay
{
let cow = try! ModelEntity.load(named: "COW_ANIMATIONS")
let horse = try! ModelEntity.load(named: "White_Horse")

cow.position.x = -1.0
horse.position.x = 1.0

let anchor = AnchorEntity()
cow.setParent(anchor)
horse.setParent(anchor)
arView.scene.anchors.append(anchor)

let cowAnimationResource = cow.availableAnimations[0]
let horseAnimationResource = horse.availableAnimations[0]

cow.playAnimation(cowAnimationResource.repeat(duration: .infinity),
                                    transitionDuration: 1.25,
                                          startsPaused: false)

horse.playAnimation(horseAnimationResource.repeat(duration: .infinity),
                                        transitionDuration: 0.75,
                                              startsPaused: false)}


  }

Answer 1

In RealityKit SDK, to play an animation contained in a single .usdz file, use the following code:

let cow = try ModelEntity.load(named: "cow")
let horse = try ModelEntity.load(named: "horse")

cow.position.x = -1.0
horse.position.x = 1.0

let anchor = AnchorEntity()
cow.setParent(anchor)
horse.setParent(anchor)
arView.scene.anchors.append(anchor)

let cowAnimationResource = cow.availableAnimations[0]
let horseAnimationResource = horse.availableAnimations[0]

cow.playAnimation(cowAnimationResource.repeat(duration: .infinity), 
                                    transitionDuration: 1.25, 
                                          startsPaused: false)

horse.playAnimation(horseAnimationResource.repeat(duration: .infinity), 
                                        transitionDuration: 0.75, 
                                              startsPaused: false)

In RealityKit 2.0, by default, you can play only the first animation contained in a single usdz file. However, there are the workaround 1 and the workaround 2.