From 5dc8d2ff781865f6dda46bacda5c528ee5c7d2a1 Mon Sep 17 00:00:00 2001
From: Nico de Poel <ndepoel@gmail.com>
Date: Tue, 10 Aug 2021 12:42:33 +0200
Subject: [PATCH] Rewrote surface grouping method to be iterative instead of
 tail-recursive. Fixes potential stack overflow issues when loading
 particularly large and complex maps.

---
 Assets/Scripts/Support/BrushModel.cs | 39 ++++++++++++++++------------
 1 file changed, 23 insertions(+), 16 deletions(-)

diff --git a/Assets/Scripts/Support/BrushModel.cs b/Assets/Scripts/Support/BrushModel.cs
index b810c33..4f982be 100644
--- a/Assets/Scripts/Support/BrushModel.cs
+++ b/Assets/Scripts/Support/BrushModel.cs
@@ -66,27 +66,34 @@ public class BrushModel
 
     private void GroupSurfaces(QNode node, QSurface[] surfaces, Dictionary<(IntPtr, int, QSurfaceFlags), List<QSurface>> surfaceGroups)
     {
-        if (node.contents < 0)  // Leaf node
-            return;
+        var nodeQueue = new Queue<QNode>();
+        nodeQueue.Enqueue(node);
 
-        for (int surfIdx = 0; surfIdx < node.numSurfaces; ++surfIdx)
+        while (nodeQueue.Count > 0)
         {
-            var surface = surfaces[node.firstSurface + surfIdx];
+            node = nodeQueue.Dequeue();
+            if (node.contents < 0)  // Leaf node
+                continue;
             
-            IntPtr texPtr = surface.TextureInfo.texture;
-            int lightNum = surface.lightmapTextureNum;
-            QSurfaceFlags flags = surface.flags;
-            var key = (texPtr, lightNum, flags);
+            for (int surfIdx = 0; surfIdx < node.numSurfaces; ++surfIdx)
+            {
+                var surface = surfaces[node.firstSurface + surfIdx];
 
-            if (!surfaceGroups.ContainsKey(key))
-                surfaceGroups[key] = new List<QSurface>();
-            
-            surfaceGroups[key].Add(surface);
-        }
+                IntPtr texPtr = surface.TextureInfo.texture;
+                int lightNum = surface.lightmapTextureNum;
+                QSurfaceFlags flags = surface.flags;
+                var key = (texPtr, lightNum, flags);
 
-        foreach (var childNode in node.Children)
-        {
-            GroupSurfaces(childNode, surfaces, surfaceGroups);
+                if (!surfaceGroups.ContainsKey(key))
+                    surfaceGroups[key] = new List<QSurface>();
+
+                surfaceGroups[key].Add(surface);
+            }
+
+            foreach (var childNode in node.Children)
+            {
+                nodeQueue.Enqueue(childNode);
+            }
         }
     }