cenkbilgen · March 12, 2019 17:38 · Mar 12, 2019
diff --git a/Origin.swift b/Origin.swift
@@ -0,0 +1,72 @@
+//
+//  OriginAxis.swift
+//
+//  Created by abc on 2019-03-07.
+//  Copyright © 2019 Cenk Bilgen. All rights reserved.
+//
+
+import Foundation
+import SceneKit
+
+class Origin: SCNNode {
+
+  // see: https://developer.apple.com/documentation/arkit/arsessionconfiguration/worldalignment/gravityandheading
+  // if ar session configured with gravity and heading, then +x is east, +y is up, +z is south
+
+  private enum Axis {
+    case x, y, z
+
+    var normal: float3 {
+      switch self {
+      case .x: return simd_float3(1, 0, 0)
+      case .y: return simd_float3(0, 1, 0)
+      case .z: return simd_float3(0, 0, 1)
+      }
+    }
+  }
+
+  // TODO: Set pivot to origin and redo tranforms, it'll make it easier to place additional nodes
+
+  init(length: CGFloat = 0.1, radiusRatio ratio: CGFloat = 0.04, color: (x: UIColor, y: UIColor, z: UIColor, origin: UIColor) = (.blue, .green, .red, .cyan)) {
+
+    // x-axis
+    let xAxis = SCNCylinder(radius: length*ratio, height: length)
+    xAxis.firstMaterial?.diffuse.contents = color.x
+    let xAxisNode = SCNNode(geometry: xAxis)
+    // by default the middle of the cylinder will be at the origin aligned to the y-axis
+    // need to spin around to align with respective axes and shift position so they start at the origin
+    xAxisNode.simdWorldOrientation = simd_quatf.init(angle: .pi/2, axis: Axis.z.normal)
+    xAxisNode.simdWorldPosition = simd_float1(length)/2 * Axis.x.normal
+
+    // y-axis
+    let yAxis = SCNCylinder(radius: length*ratio, height: length)
+    yAxis.firstMaterial?.diffuse.contents = color.y
+    let yAxisNode = SCNNode(geometry: yAxis)
+    yAxisNode.simdWorldPosition = simd_float1(length)/2 * Axis.y.normal // just shift
+
+    // z-axis
+    let zAxis = SCNCylinder(radius: length*ratio, height: length)
+    zAxis.firstMaterial?.diffuse.contents = color.z
+    let zAxisNode = SCNNode(geometry: zAxis)
+    zAxisNode.simdWorldOrientation = simd_quatf(angle: -.pi/2, axis: Axis.x.normal)
+    zAxisNode.simdWorldPosition = simd_float1(length)/2 * Axis.z.normal
+
+    // dot at origin
+    let origin = SCNSphere(radius: length*ratio)
+    origin.firstMaterial?.diffuse.contents = color.origin
+    let originNode = SCNNode(geometry: origin)
+
+    super.init()
+
+    self.addChildNode(originNode)
+    self.addChildNode(xAxisNode)
+    self.addChildNode(yAxisNode)
+    self.addChildNode(zAxisNode)
+
+  }
+
+  required init?(coder aDecoder: NSCoder) {
+    super.init(coder: aDecoder)
+  }
+
+}