SceneKitBoundingBox.swift

import SceneKit

struct SceneKitBoundingBox {
	let backLeftTop: SCNVector3
	let backLeftBottom: SCNVector3
	
	let backRightTop: SCNVector3
	let backRightBottom: SCNVector3
	
	let frontLeftTop: SCNVector3
	let frontLeftBottom: SCNVector3
	
	let fromRightTop: SCNVector3
	let fromRightBottom: SCNVector3
	
	init(min: SCNVector3, max: SCNVector3) {
		self.backLeftTop = SCNVector3(min.x, min.y, max.z)
		self.backLeftBottom = SCNVector3(min.x, min.y, min.z)
		
		self.backRightTop = SCNVector3(max.x, min.y, max.z)
		self.backRightBottom = SCNVector3(max.x, min.y, min.z)
		
		self.frontLeftTop = SCNVector3(min.x, max.y, max.z)
		self.frontLeftBottom = SCNVector3(min.x, max.y, min.z)
		
		self.fromRightTop = SCNVector3(max.x, max.y, max.z)
		self.fromRightBottom = SCNVector3(max.x, max.y, min.z)
	}
}


func convertToScreen(coord: SCNVector3, fromNode: SCNNode) -> CGPoint {
	let converted: SCNVector3 = fromNode.convertPosition(coord, to: nil)
	let projectedPoint: SCNVector3 = self.sceneView.projectPoint(converted)
	
	let point = CGPoint(
		x: CGFloat(projectedPoint.x),
		y: CGFloat(projectedPoint.y)
	)
	return point
}

	
struct ScreenBoundingBox {
	let backLeftTop: CGPoint
	let backLeftBottom: CGPoint
	
	let backRightTop: CGPoint
	let backRightBottom: CGPoint
	
	let frontLeftTop: CGPoint
	let frontLeftBottom: CGPoint
	
	let fromRightTop: CGPoint
	let fromRightBottom: CGPoint
	
	init(boundingBox: SceneKitBoundingBox, fromNode: SCNNode, convertToScreen: (SCNVector3, SCNNode) -> CGPoint) {
		self.backLeftTop = convertToScreen(boundingBox.backLeftTop, fromNode)
		self.backLeftBottom = convertToScreen(boundingBox.backLeftBottom, fromNode)
		self.backRightTop = convertToScreen(boundingBox.backRightTop, fromNode)
		self.backRightBottom = convertToScreen(boundingBox.backRightBottom, fromNode)
		self.frontLeftTop = convertToScreen(boundingBox.frontLeftTop, fromNode)
		self.frontLeftBottom = convertToScreen(boundingBox.frontLeftBottom, fromNode)
		self.fromRightTop = convertToScreen(boundingBox.fromRightTop, fromNode)
		self.fromRightBottom = convertToScreen(boundingBox.fromRightBottom, fromNode)
	}
	
	private var points: [CGPoint] {
		return [
			self.backLeftTop,
			self.backLeftBottom,
			self.backRightTop,
			self.backRightBottom,
			self.frontLeftTop,
			self.frontLeftBottom,
			self.fromRightTop,
			self.fromRightBottom,
		]
	}
	
	var minX: CGPoint {
		return self.points.min(by: { $0.x < $1.x })!
	}
	var maxX: CGPoint {
		return self.points.max(by: { $0.x < $1.x })!
	}
	
	var minY: CGPoint {
		return self.points.min(by: { $0.y < $1.y })!
	}
	var maxY: CGPoint {
		return self.points.max(by: { $0.y < $1.y })!
	}
}


private func fixFieldOfView() {
	guard let scene: SCNScene = self.scene else { return }
	
	if let firstChild: SCNNode = scene.rootNode.childNodes.first {
		let boundingBox = firstChild.boundingBox
		
		let fullBoundingBox = SceneKitBoundingBox(min: boundingBox.min, max: boundingBox.max)
		
		let screenBoundingBox = ScreenBoundingBox(
			boundingBox: fullBoundingBox,
			fromNode: firstChild,
			convertToScreen: self.convertToScreen(coord:fromNode:)
		)
		
		let minX: CGFloat = screenBoundingBox.minX.x
		let maxX: CGFloat = screenBoundingBox.maxX.x
		
		let minY: CGFloat = screenBoundingBox.minY.y
		let maxY: CGFloat = screenBoundingBox.maxY.y
		
		print("minX: \(minX) - maxX: \(maxX)")
		print("minY: \(minY) - maxY: \(maxY)")
		
		let totalWidth: CGFloat = (maxX - minX)
		
		let scaleX = totalWidth / self.screenWidth
		
		print("totalWidth: \(totalWidth) - screenWidth: \(self.screenWidth) - scaleX: \(scaleX)")
		
		if let cameraNode = self.sceneView.pointOfView, let camera = cameraNode.camera {
			let fieldOfView = String(format: "%.3f", camera.fieldOfView)
			
			print("camera: \(camera) - fieldOfView: \(fieldOfView) - position: \(cameraNode.position)")
			
			if scaleX > 1 {
				let fieldOfView: CGFloat = camera.fieldOfView
				let newFieldOfView: CGFloat = fieldOfView  / (1.0 / scaleX)
				camera.fieldOfView = newFieldOfView
				
				print("fieldOfView: \(fieldOfView) - newFieldOfView: \(newFieldOfView)")
			}
		}
	}
	
	DispatchQueue.main.async(execute: {
		self.sceneView.alpha = 1
	})
}