visionOS sample code: add view model, get Mesh construction off the main thread

ExampleVisionOS/Assets.xcassets/AppIcon.solidimagestack/Back.solidimagestacklayer/Content.imageset/Contents.json

@@ -0,0 +1,12 @@
+{
+  "images" : [
+    {
+      "idiom" : "vision",
+      "scale" : "2x"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

ExampleVisionOS/Assets.xcassets/AppIcon.solidimagestack/Back.solidimagestacklayer/Contents.json

@@ -0,0 +1,6 @@
+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

ExampleVisionOS/Assets.xcassets/AppIcon.solidimagestack/Contents.json

@@ -0,0 +1,17 @@
+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  },
+  "layers" : [
+    {
+      "filename" : "Front.solidimagestacklayer"
+    },
+    {
+      "filename" : "Middle.solidimagestacklayer"
+    },
+    {
+      "filename" : "Back.solidimagestacklayer"
+    }
+  ]
+}

ExampleVisionOS/Assets.xcassets/AppIcon.solidimagestack/Front.solidimagestacklayer/Content.imageset/Contents.json

@@ -0,0 +1,12 @@
+{
+  "images" : [
+    {
+      "idiom" : "vision",
+      "scale" : "2x"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

ExampleVisionOS/Assets.xcassets/AppIcon.solidimagestack/Front.solidimagestacklayer/Contents.json

@@ -0,0 +1,6 @@
+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

ExampleVisionOS/Assets.xcassets/AppIcon.solidimagestack/Middle.solidimagestacklayer/Content.imageset/Contents.json

@@ -0,0 +1,12 @@
+{
+  "images" : [
+    {
+      "idiom" : "vision",
+      "scale" : "2x"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

ExampleVisionOS/Assets.xcassets/AppIcon.solidimagestack/Middle.solidimagestacklayer/Contents.json

@@ -0,0 +1,6 @@
+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

ExampleVisionOS/Assets.xcassets/Contents.json

@@ -0,0 +1,6 @@
+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

ExampleVisionOS/ContentView.swift

@@ -0,0 +1,22 @@
+//
+//  ContentView.swift
+//  ExampleVisionOS
+//
+//  Created by Hal Mueller on 3/5/24.
+//  Copyright © 2024 Nick Lockwood. All rights reserved.
+//
+
+import RealityKit
+import SwiftUI
+
+struct ContentView: View {
+    @State private var enlarge = false
+
+    var body: some View {
+        VolumetricView()
+    }
+}
+
+#Preview(windowStyle: .volumetric) {
+    ContentView()
+}

ExampleVisionOS/ExampleVisionOSApp.swift

@@ -0,0 +1,20 @@
+//
+//  ExampleVisionOSApp.swift
+//  ExampleVisionOS
+//
+//  Created by Hal Mueller on 3/5/24.
+//  Copyright © 2024 Nick Lockwood. All rights reserved.
+//
+
+import SwiftUI
+
+@main
+struct ExampleVisionOSApp: App {
+    var body: some Scene {
+        WindowGroup {
+            ContentView()
+        }
+        .windowStyle(.volumetric)
+        .defaultSize(width: 1.5, height: 1.5, depth: 1.5, in: .meters)
+    }
+}

ExampleVisionOS/Info.plist

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>UIApplicationSceneManifest</key>
+	<dict>
+		<key>UIApplicationPreferredDefaultSceneSessionRole</key>
+		<string>UIWindowSceneSessionRoleVolumetricApplication</string>
+		<key>UIApplicationSupportsMultipleScenes</key>
+		<true/>
+		<key>UISceneConfigurations</key>
+		<dict/>
+	</dict>
+</dict>
+</plist>

ExampleVisionOS/MeshViewModel.swift

@@ -0,0 +1,65 @@
+//
+//  MeshViewModel.swift
+//  Euclid
+//
+//  Created by Hal Mueller on 3/11/24.
+//  Copyright © 2024 Nick Lockwood. All rights reserved.
+//
+
+import CoreGraphics
+import Euclid
+import RealityKit
+
+/// Holds an Entity built from a Euclid Mesh, plus state for the VolumetricView.
+@Observable
+class MeshViewModel: ObservableObject {
+    /// The Euclid mesh's Entity lands here.
+    public var entity: Entity? = nil
+    /// Euclid has finished preparing the content.
+    public var contentReady = false
+    /// The RealityView instance has added the content.
+    public var contentAdded = false
+
+    /// A demonstration Mesh generated by Euclid
+    private let euclidMesh: Mesh = {
+        let start = CFAbsoluteTimeGetCurrent()
+
+        // create some geometry using Euclid
+        let cube = Mesh.cube(size: 0.8, material: Color.red)
+        let sphere = Mesh.sphere(slices: 120, material: CGImage.checkerboard())
+        let mesh = cube.subtracting(sphere).makeWatertight()
+
+        print("Time:", CFAbsoluteTimeGetCurrent() - start)
+        print("Polygons:", mesh.polygons.count)
+        print("Triangles:", mesh.triangulate().polygons.count)
+        print("Watertight:", mesh.isWatertight)
+
+        // Sleep here to simulate a long-running mesh construction.
+        sleep(5)
+
+        return mesh
+    }()
+
+    func prepareContent() {
+        Task.init {
+            do {
+                let demoBoxEntity = try await ModelEntity(euclidMesh.scaled(by: 0.5))
+
+                // for more realism, add a shadow
+                await demoBoxEntity.components.set(GroundingShadowComponent(castsShadow: true))
+
+                // needed for tap detection/response
+                await demoBoxEntity.generateCollisionShapes(recursive: true)
+
+                // for gesture targeting
+                await demoBoxEntity.components.set(InputTargetComponent())
+
+                print(#function, "complete")
+                entity = demoBoxEntity
+                contentReady = true
+            } catch {
+                print(#function, "failed to update content")
+            }
+        }
+    }
+}

ExampleVisionOS/Preview Content/Preview Assets.xcassets/Contents.json

@@ -0,0 +1,6 @@
+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

ExampleVisionOS/VolumetricView.swift

@@ -0,0 +1,60 @@
+//
+//  VolumetricView.swift
+//  ExampleVisionOS
+//
+//  Created by Hal Mueller on 3/6/24.
+//  Copyright © 2024 Nick Lockwood. All rights reserved.
+//
+
+import RealityKit
+import SwiftUI
+
+struct VolumetricView: View {
+    @State private var spinX = 0.0
+    @State private var spinY = 0.0
+
+    private var viewModel = MeshViewModel()
+
+    var body: some View {
+        RealityView { content in
+            // In this demo we'll skip adding content at init time. But if you have other content
+            // that you want visible while the EuclidMesh is being built, add it in this closure.
+            // A simulated expensive, long-running Mesh generation happens on its own Task.
+            debugPrint(content)
+        } update: { content in
+            if viewModel.contentReady,
+               !viewModel.contentAdded,
+               let box = viewModel.entity
+            {
+                content.add(box)
+                viewModel.contentAdded = true
+            }
+            guard let entity = content.entities.first else {
+                return
+            }
+
+            let pitch = Transform(pitch: Float(spinX * -1)).matrix
+            let yaw = Transform(yaw: Float(spinY)).matrix
+            entity.transform.matrix = pitch * yaw
+        }
+        .gesture(
+            DragGesture(minimumDistance: 0)
+                .targetedToAnyEntity()
+                .onChanged { value in
+                    let startLocation = value.convert(value.startLocation3D, from: .local, to: .scene)
+                    let currentLocation = value.convert(value.location3D, from: .local, to: .scene)
+                    let delta = currentLocation - startLocation
+                    spinX = Double(delta.y) * 5
+                    spinY = Double(delta.x) * 5
+                }
+        )
+        .task {
+            viewModel.prepareContent()
+            print("content preparation launched...")
+        }
+    }
+}
+
+#Preview {
+    VolumetricView()
+}

README.md

@@ -58,9 +58,10 @@ Feel free to open an issue in Github if you have questions about how to use the
 If you wish to contribute improvements to the documentation or the code itself, that's great! But please read the [CONTRIBUTING.md](CONTRIBUTING.md) file before submitting a pull request.
 
 
-# Example
+# Example and ExampleVisionOS
 
-See the included project for an example of how Euclid can be used in conjunction with SceneKit or RealityKit to generate and render a nontrivial 3D shape on iOS.
+See the included projects for examples of how Euclid can be used in conjunction with SceneKit or RealityKit to generate and render a nontrivial 3D shape. `Example` uses storyboards, is built for iOS, and runs in "Designed for iPad" mode on macOS and visionOS.
+`ExampleVisionPro` uses SwiftUI and a RealityView in a volumetric window, and runs only on visionOS.
 
 
 # Documentation