From 5804ee53d3dab3e1a6c01479c349ca37d214b12c Mon Sep 17 00:00:00 2001
From: Marc Alexander <Pilot-Marc@users.noreply.github.com>
Date: Sun, 8 Sep 2019 10:32:44 -0500
Subject: [PATCH] render distant nodes behind closer nodes (#220)

* render distant nodes behind closer nodes

* Use common code to calculate rendering order
Code style changes to match rest of code base

* Method comments get the triple slash treatment

* Update changelog
---
 .../Extensions/SCNNode+Extensions.swift              |  1 +
 .../Nodes/LocationAnnotationNode.swift               |  2 ++
 Sources/ARKit-CoreLocation/Nodes/LocationNode.swift  | 12 ++++++++++++
 changelog.md                                         |  1 +
 4 files changed, 16 insertions(+)

diff --git a/Sources/ARKit-CoreLocation/Extensions/SCNNode+Extensions.swift b/Sources/ARKit-CoreLocation/Extensions/SCNNode+Extensions.swift
index e08c819f..e074d766 100644
--- a/Sources/ARKit-CoreLocation/Extensions/SCNNode+Extensions.swift
+++ b/Sources/ARKit-CoreLocation/Extensions/SCNNode+Extensions.swift
@@ -12,6 +12,7 @@ extension SCNNode {
     /// Overlapping nodes require unique renderingOrder values to avoid flicker
     /// This method will select random values if you don't care which node is in front of the other,
     /// or you can specify a particular z-order value
+    /// Note: rendering order will be changed later based on distance from camera
     func removeFlicker (withRenderingOrder renderingOrder: Int = Int.random(in: 1..<Int.max)) {
         self.renderingOrder = renderingOrder
         if let geom = geometry {
diff --git a/Sources/ARKit-CoreLocation/Nodes/LocationAnnotationNode.swift b/Sources/ARKit-CoreLocation/Nodes/LocationAnnotationNode.swift
index 710a918d..27a821a6 100644
--- a/Sources/ARKit-CoreLocation/Nodes/LocationAnnotationNode.swift
+++ b/Sources/ARKit-CoreLocation/Nodes/LocationAnnotationNode.swift
@@ -59,6 +59,8 @@ open class LocationAnnotationNode: LocationNode {
 
         let distance = self.location(locationManager.bestLocationEstimate).distance(from: location)
 
+        childNodes.first?.renderingOrder = renderingOrder(fromDistance: distance)
+
         let adjustedDistance = self.adjustedDistance(setup: setup, position: position,
                                                      locationNodeLocation: nodeLocation, locationManager: locationManager)
 
diff --git a/Sources/ARKit-CoreLocation/Nodes/LocationNode.swift b/Sources/ARKit-CoreLocation/Nodes/LocationNode.swift
index 5fac4a85..60ef9c3b 100644
--- a/Sources/ARKit-CoreLocation/Nodes/LocationNode.swift
+++ b/Sources/ARKit-CoreLocation/Nodes/LocationNode.swift
@@ -156,6 +156,11 @@ open class LocationNode: SCNNode {
         SCNTransaction.begin()
         SCNTransaction.animationDuration = setup ? 0.0 : 0.1
 
+        let distance = self.location(locationManager.bestLocationEstimate).distance(from:
+            locationManager.currentLocation ?? nodeLocation)
+
+        childNodes.first?.renderingOrder = renderingOrder(fromDistance: distance)
+
         _ = self.adjustedDistance(setup: setup, position: position,
                                   locationNodeLocation: nodeLocation, locationManager: locationManager)
 
@@ -163,4 +168,11 @@ open class LocationNode: SCNNode {
 
         onCompletion()
     }
+	
+    /// Converts distance from meters to SCNKit rendering order
+    /// Constant multiplier eliminates flicker caused by slight distance variations
+    /// Nodes with greater rendering orders are rendered last
+    func renderingOrder(fromDistance distance: CLLocationDistance) -> Int {
+        return Int.max - 1000 - (Int(distance * 1000))
+    }
 }
diff --git a/changelog.md b/changelog.md
index 3694011e..c8d10f7f 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,6 @@
 # Changelog
 - 1.2.2
+   - [PR #220 - Render distant nodes behind closer nodes ](https://github.com/ProjectDent/ARKit-CoreLocation/pull/220)
 - 1.2.1
     - [PR #207 - Addresses Issue #136 - ARCL lacks CI ](https://github.com/ProjectDent/ARKit-CoreLocation/pull/207)
     - [PR #209 - Updates polyline position/scale when GPS location is updated](https://github.com/ProjectDent/ARKit-CoreLocation/pull/209)