SceneKit – Changing colors of USDZ model

Question

I created a view with SceneKit using a USDZ file, how can I change the colors of a particular material from gray to something else directly in the SwiftUI code?

var scene = SCNScene(named: "2020_BMW_M5.usdz")
var body: some View {       
    VStack {
        SceneView(scene: scene, 
                options: [.autoenablesDefaultLighting, .allowsCameraControl])
    }
}

Answer 1

Use a subscript approach (.childNodes[n].childNodes[n].childNodes[n]) to get to model in desired hierarchy, and then change its color as usually:

import SwiftUI
import SceneKit

struct ContentView : View {
    var body: some View {
        return SceneKitViewContainer().ignoresSafeArea()
    }
}

struct SceneKitViewContainer: UIViewRepresentable {
    
    func makeUIView(context: Context) -> SCNView {
        let scnView = SCNView(frame: .zero)
        scnView.allowsCameraControl = true
        scnView.autoenablesDefaultLighting = true
        scnView.scene = SCNScene(named: "Model.usdz")
        
        let model = scnView.scene?.rootNode.childNode(withName: "SomeModel", 
                                                   recursively: true)
        model?.childNodes[1].geometry?.firstMaterial?.diffuse.contents = 
                                                                UIColor.red
        print(model?.childNodes[1])

        return scnView
    }
    func updateUIView(_ uiView: SCNView, context: Context) { }
}