RealityKit is making my iPhone thermalStatus go crazy with no apparent reason - ios

Question

I have the following demo app, In which I set an ARWorldTrackingConfiguration over my RealityKit.
I also use plane detection.
When a plane is detected, I add the ability to "Fire" a rectangle on to the plane with a simple square collision box.
After about 100 squares, the app thermalStatus changes to serious and my frame rate goes down to 30fps.
For the life of me, I can't understand why 100 simple shapes in an RealityKit world, with no special textures or even collision events will cause this.
Does anyone have any idea?
PS1: Running this on an iPhone XS, which should be able to perform better according to HW specifications.
PS2: Adding the code below
import UIKit
import RealityKit
import ARKit
let material = SimpleMaterial(color: .systemPink, isMetallic: false)
var sphere: MeshResource = MeshResource.generatePlane(width: 0.1, depth: 0.1)
var box = ShapeResource.generateBox(width: 0.1, height: 0.03, depth: 0.1)
var ballEntity = ModelEntity(mesh: sphere, materials: [material])
let collider = CollisionComponent(
shapes: [box],
mode: .trigger
)
class ViewController: UIViewController {
#IBOutlet var arView: ARView!
#IBOutlet weak var button: UIButton!
override func viewDidLoad() {
super.viewDidLoad()
let configuration = ARWorldTrackingConfiguration()
configuration.planeDetection = [.vertical]
configuration.worldAlignment = .camera
// Add the box anchor to the scene
configuration.frameSemantics.remove(.bodyDetection)
configuration.frameSemantics.remove(.personSegmentation)
configuration.frameSemantics.remove(.personSegmentationWithDepth)
arView.renderOptions.insert(.disableCameraGrain)
arView.renderOptions.insert(.disableGroundingShadows)
arView.renderOptions.insert(.disableHDR)
arView.renderOptions.insert(.disableMotionBlur)
arView.renderOptions.insert(.disableFaceOcclusions)
arView.renderOptions.insert(.disableDepthOfField)
arView.renderOptions.insert(.disablePersonOcclusion)
configuration.planeDetection = [.vertical, .horizontal]
arView.debugOptions = [.showAnchorGeometry, .showStatistics]
let gesture = UITapGestureRecognizer(target: self,
action: #selector(self.tap(_:)))
arView.addGestureRecognizer(gesture)
arView.session.run(configuration, options: [ .resetSceneReconstruction ])
}
#objc func tap(_ sender: UITapGestureRecognizer) {
let point: CGPoint = sender.location(in: arView)
guard let query = arView.makeRaycastQuery(from: point,
allowing: .existingPlaneGeometry,
alignment: .vertical) else {
return
}
let result = arView.session.raycast(query)
guard let raycastResult = result.first else { return }
let anchor = AnchorEntity(raycastResult: raycastResult)
var ballEntity = ModelEntity(mesh: sphere, materials: [material])
ballEntity.collision = collider
anchor.addChild(ballEntity)
arView.scene.anchors.append(anchor)
}
#IBAction func removePlaneDebugging(_ sender: Any) {
if arView.debugOptions.contains(.showAnchorGeometry) {
arView.debugOptions.remove(.showAnchorGeometry)
button.setTitle("Display planes", for: .normal)
return
}
button.setTitle("Remove planes", for: .normal)
arView.debugOptions.insert(.showAnchorGeometry)
}
}
Can anyone please assist?

Answer 1

When you use ARKit or RealityKit, a thermal condition of your iPhone doesn't entirely depend on a realtime rendering of 100 primitives. The point is a 6-DOF world tracking running at 60 fps. Plane Detection is another hard core feature for your device. So, World Tracking and Plane Detection ops are extremely CPU/GPU intensive (as well as Image/Object Detection or People Occlusion). They also quickly drain your battery.
Another heavy burden for your CPU/GPU are shadows and reflective metallic shaders. Realtime 60 fps soft shadows are additional task for any device (even with A12 processor) and metallic textures that use environment reflectons are calculated on neural engines.