RealityKit instancing

gistfile1.txt

import AppKit
import RealityKit

class GameViewController: NSViewController {
    
    @IBOutlet var arView: ARView!
    
    override func awakeFromNib() {
        
        // Generating the initial mesh (just so that we can extract its MeshResource.Model, which contains the actual mesh data)
        let mesh = MeshResource.generateBox(size: 1)
             
        // Making sure our assumption that the mesh contains a single model is true.
        precondition(mesh.contents.models.count == 1)
        // Extracting the model.
        let model = mesh.contents.models.map { model in
            model
        }.first!
        
        // Create a new `Contents`, this will hold the model and the instances of that model.
        var contents = MeshResource.Contents()
        
        // Add the model.
        contents.models.insert(model)
        
        // Generate this many instances.
        let instanceCount = 20
        
        for index in 0..<instanceCount {
            
            // Build the transform for this instance.
            var transform = Transform()
            // Distribute the intances along the x-axis.
            transform.translation.x = 2 * Float(index) - Float(instanceCount)
            
            // Create the instance, referencing the model id that you want to instance, and the transform matrix of the instance.
            let instance = MeshResource.Instance(id: "Instance \(index)", model: model.id, at: transform.matrix)
            
            // Add the instance.
            contents.instances.insert(instance)
        }
        
        // Create an instanced mesh resource from the new contents.
        let instancedMesh = try! MeshResource.generate(from: contents)
                
        // Create a ModelComponent using the instanced mesh.
        let material = SimpleMaterial(color: .red, isMetallic: false)
        let modelComponent = ModelComponent(mesh: instancedMesh, materials: [material])
        
        // Set the ModelComponent on a ModelEntity.
        let modelEntity = ModelEntity()
        modelEntity.model = modelComponent
        
        // Anchor the ModelEntity into the scene
        let anchorEntity = AnchorEntity()
        
        anchorEntity.position.z = -30
        
        anchorEntity.addChild(modelEntity)
        
        arView.scene.addAnchor(anchorEntity)
    }
}