RealityKit removing old 3D objects from scene before adding new 3D objects - swift

Question

I'm trying to play with Apple's RealityKit and some usdz files I got from their website.
I made a small app where I can load each 3D model at a time.
It works but with one issue. If I add a single 3D object is fine but when I load the new models they all get stuck upon each other. I can't seem to figure out how to remove the old 3D object before adding a different one.
Here is my code
My Model object
import Foundation
import UIKit
import RealityKit
import Combine
class Model {
var modelName: String
var image: UIImage
var modelEntity: ModelEntity?
private var cancellable: AnyCancellable? = nil
var message: String = ""
init(modelName: String){
self.modelName = modelName
self.image = UIImage(named: modelName)!
let filename = modelName + ".usdz"
self.cancellable = ModelEntity.loadModelAsync(named: filename)
.sink(receiveCompletion: { completion in
switch completion {
case .finished:
print("Model.swift -> DEBUG: Succesfully loaded \(self.modelName)")
break
case .failure(let error):
print("Model.swift -> DEBUG: Unable to load : \(self.modelName)")
self.message = error.localizedDescription
}
}, receiveValue: { modelEntity in
//get model entity
self.modelEntity = modelEntity
})
}
}
RealityKit and SwiftUI View
import SwiftUI
import RealityKit
import ARKit
struct ContentView : View {
#State private var isPlacementEnabled = false
#State private var selectedModel: Model?
#State private var modelConfirmedForPlacement: Model?
private var models: [Model] {
//Dynamicaly get file names
let filemanager = FileManager.default
guard let path = Bundle.main.resourcePath,
let files = try? filemanager.contentsOfDirectory(atPath: path)
else {
return []
}
var availableModels: [Model] = []
for filename in files where filename.hasSuffix("usdz") {
let modelName = filename.replacingOccurrences(of: ".usdz", with: "")
let model = Model(modelName: modelName)
availableModels.append(model)
}
return availableModels
}
var body: some View {
ZStack(alignment: .bottom){
ARViewContainer(modelConfirmedForPlacement: self.$modelConfirmedForPlacement)
if self.isPlacementEnabled {
PlacementButtonsView(isPlacementEnabled: self.$isPlacementEnabled,
selectedModel: self.$selectedModel,
modelConfirmedForPlacement: self.$modelConfirmedForPlacement
)
}
else {
ModelPickerView(models: self.models,
isPlacementEnabled: self.$isPlacementEnabled,
selectedModel: self.$selectedModel)
}
}
}
}
struct ARViewContainer: UIViewRepresentable {
#Binding var modelConfirmedForPlacement: Model?
var anchorEntity = AnchorEntity(world: .init(x: 0, y: 0, z: 0))
func makeUIView(context: Context) -> ARView {
let arView = ARView(frame: .zero)
let config = ARWorldTrackingConfiguration()
config.planeDetection = [.horizontal, .vertical ]
config.environmentTexturing = .automatic
if ARWorldTrackingConfiguration.supportsSceneReconstruction(.mesh){
config.sceneReconstruction = .mesh
}
arView.session.run(config)
return arView
}
func updateUIView(_ uiView: ARView, context: Context) {
//Here is where I try to remove the old 3D Model before loading the new one
if self.modelConfirmedForPlacement?.modelEntity != nil {
uiView.scene.anchors.first?.removeChild((self.modelConfirmedForPlacement?.modelEntity)!)
anchorEntity.scene?.removeAnchor(anchorEntity)
self.anchorEntity.removeChild((self.modelConfirmedForPlacement?.modelEntity)!)
}
if let model = self.modelConfirmedForPlacement{
if model.modelEntity != nil {
print("ARContainer -> DEBUG: adding model to scene - \(model.modelName)" )
}
else{
print("ARContainer -> DEBUG: Unable to load model entity for - \(model.modelName)" )
}
DispatchQueue.main.async {
let modelEntity = try? Entity.load( named: model.modelName + ".usdz")
anchorEntity.addChild(modelEntity!)
uiView.scene.addAnchor(anchorEntity)
}
}
}
}
struct ModelPickerView: View {
var models: [Model]
#Binding var isPlacementEnabled: Bool
#Binding var selectedModel: Model?
var body: some View {
ScrollView(.horizontal, showsIndicators: false){
HStack(spacing: 30){
ForEach(0 ..< self.models.count , id: \.self){ index in
Button {
// print("DEBUG : selected model with name: \(self.models[index].modelName)")
self.isPlacementEnabled = true
self.selectedModel = self.models[index]
} label: {
Image(uiImage: self.models[index].image)
.resizable()
.frame(height: 80 )
.aspectRatio(1/1, contentMode: .fit)
.background(Color.white)
.cornerRadius(12)
}
.buttonStyle(PlainButtonStyle())
}
}
}
.padding(20)
.background(Color.black.opacity(0.5))
}
}
struct PlacementButtonsView: View {
#Binding var isPlacementEnabled: Bool
#Binding var selectedModel: Model?
#Binding var modelConfirmedForPlacement: Model?
var body: some View {
HStack{
//Cancel button
Button {
// print("DEBUG: model ploacement cancelled")
self.resetPlacementParameters()
} label: {
Image(systemName: "xmark")
.frame(width: 60, height: 60)
.font(.title)
.background(Color.white.opacity(0.75))
.cornerRadius(30)
.padding(20)
}
//Confirm button
Button {
// print("DEBUG: model ploacement confirmed")
self.modelConfirmedForPlacement = self.selectedModel
self.resetPlacementParameters()
} label: {
Image(systemName: "checkmark")
.frame(width: 60, height: 60)
.font(.title)
.background(Color.white.opacity(0.75))
.cornerRadius(30)
.padding(20)
}
}
}
func resetPlacementParameters(){
self.isPlacementEnabled = false
self.selectedModel = nil
}
}
#if DEBUG
struct ContentView_Previews : PreviewProvider {
static var previews: some View {
ContentView()
}
}
#endif