How to show WorldOrigin axis in SceneKit scene for macOS? - macos

Question

I am building a macOS SwiftUI app. I want to show the world axis such that the user is aware of the orientation of objects. I've looked at the documentation, but the showWorldOrigin debug setting is not available on macOS. Is there an alternative way to show the world axis that I am missing?
While I've found external libraries that create a world axis and add nodes to the scene, I was hoping there was a built-in method to simplify the task and reduce any error.

Answer 1

You can create your own sample of procedural world axis for macOS 3D app.
SwiftUI mac version
import SwiftUI
import SceneKit
struct ContentView : View {
#State private var scene = SCNScene()
#State private var axis = SCNNode()
var options: SceneView.Options = [.allowsCameraControl]
var body: some View {
ZStack {
SceneView(scene: scene, options: options).ignoresSafeArea()
let _ = scene.background.contents = NSColor.black
let _ = createWorldAxis()
let _ = axis.opacity = 0.1 // you can hide world axis
}
}
func createWorldAxis() {
let colors: [NSColor] = [.systemRed, .systemGreen, .systemBlue]
for index in 0...2 {
let box = SCNBox(width: 0.200, height: 0.005,
length: 0.005, chamferRadius: 0.001)
let material = SCNMaterial()
material.lightingModel = .constant
material.diffuse.contents = colors[index]
box.materials[0] = material
let node = SCNNode(geometry: box)
switch index {
case 0:
node.position.x += 0.1
case 1:
node.eulerAngles = SCNVector3(0, 0, Float.pi/2)
node.position.y += 0.1
case 2:
node.eulerAngles = SCNVector3(0, -Float.pi/2, 0)
node.position.z += 0.1
default: break
}
axis.addChildNode(node)
axis.scale = SCNVector3(1.5, 1.5, 1.5)
scene.rootNode.addChildNode(axis)
}
print(axis.position)
}
}
Cocoa version
import Cocoa
import SceneKit
class ViewController : NSViewController {
var axis = SCNNode()
var sceneView = SCNView()
override func viewDidLoad() {
super.viewDidLoad()
sceneView = self.view as! SCNView
sceneView.scene = SCNScene()
sceneView.allowsCameraControl = true
sceneView.backgroundColor = .black
self.createWorldAxis()
axis.opacity = 0.1 // you can hide world axis
}
func createWorldAxis() {
let colors: [NSColor] = [.systemRed, .systemGreen, .systemBlue]
for index in 0...2 {
let box = SCNBox(width: 0.200, height: 0.005,
length: 0.005, chamferRadius: 0.001)
let material = SCNMaterial()
material.lightingModel = .constant
material.diffuse.contents = colors[index]
box.materials[0] = material
let node = SCNNode(geometry: box)
if index == 0 {
node.position.x += 0.1
} else if index == 1 {
node.eulerAngles = SCNVector3(0, 0, Float.pi/2)
node.position.y += 0.1
} else if index == 2 {
node.eulerAngles = SCNVector3(0, -Float.pi/2, 0)
node.position.z += 0.1
}
axis.addChildNode(node)
axis.scale = SCNVector3(1.5, 1.5, 1.5)
sceneView.scene?.rootNode.addChildNode(axis)
}
print(axis.position)
}
}

Answer 2

Posting this answer, as per OP comments...
Apple's docs list the following SCNDebugOptions:
.showPhysicsShapes
.showBoundingBoxes
.showLightInfluences
.showLightExtents
.showPhysicsFields
.showWireframe
.renderAsWireframe
.showSkeletons
.showCreases
.showConstraints
.showCameras
.showFeaturePoints
.showWorldOrigin
Curiously, the last two - .showFeaturePoints and .showWorldOrigin - are not defined in SceneKit. And the discussion notes refer only to ARKit, where they are defined.
The docs for SCNDebugOptions state that these are bit mask patterns ... and if we print them out, we get:
showPhysicsShapes: SCNDebugOptions(rawValue: 1)
showBoundingBoxes: SCNDebugOptions(rawValue: 2)
showLightInfluences: SCNDebugOptions(rawValue: 4)
showLightExtents: SCNDebugOptions(rawValue: 8)
showPhysicsFields: SCNDebugOptions(rawValue: 16)
showWireframe: SCNDebugOptions(rawValue: 32)
renderAsWireframe: SCNDebugOptions(rawValue: 64)
showSkeletons: SCNDebugOptions(rawValue: 128)
showCreases: SCNDebugOptions(rawValue: 256)
showConstraints: SCNDebugOptions(rawValue: 512)
showCameras: SCNDebugOptions(rawValue: 1024)
So... we try this to get "the next one in order" (expecting it to equate to .showFeaturePoints):
sceneView.debugOptions = SCNDebugOptions(rawValue: 2048)
Turns out, that gives us RGB axis indicators ... the .showWorldOrigin.
For a simple scene with an extruded bezier path (a cube), using these options:
sceneView.debugOptions = [.renderAsWireframe, SCNDebugOptions(rawValue: 2048)]
we get this output:
Trying one further, thinking maybe we get .showFeaturePoints:
sceneView.debugOptions = SCNDebugOptions(rawValue: 4096)
doesn't seem to do anything - at least, I don't see any visual change in my simple Scene.

Answer 3

I found what i wanted using the UI. First, ensure you enable controls for your scene:
myscene.showsStatistics = true
Then, click the configuration button on the bottom of your screen.
In the options dropdown select World Origin.
I am puzzled why all debug options can be invoked programmatically except the World Origin. None the less, that allows you to see axis.