reworked mesh decimation yes

LightlessSync/ThirdParty/Nanomesh/Collections/CollectionUtils.cs

@@ -0,0 +1,52 @@
+using System;
+using System.Collections.Generic;
+
+namespace Nanomesh
+{
+    public static class CollectionUtils
+    {
+        public static T[] ToArray<T>(this HashSet<T> items, ref T[] array)
+        {
+            int i = 0;
+            foreach (T item in items)
+            {
+                array[i++] = item;
+            }
+
+            return array;
+        }
+
+        public static bool TryAdd<K, V>(this Dictionary<K, V> dictionary, K key, V value)
+        {
+            if (dictionary.ContainsKey(key))
+            {
+                return false;
+            }
+
+            dictionary.Add(key, value);
+            return true;
+        }
+
+        public static bool TryAdd<K, V>(this Dictionary<K, V> dictionary, K key, Func<K, V> valueFactory)
+        {
+            if (dictionary.ContainsKey(key))
+            {
+                return false;
+            }
+
+            dictionary.Add(key, valueFactory(key));
+            return true;
+        }
+
+        public static V GetOrAdd<K, V>(this Dictionary<K, V> dictionary, K key, V value)
+        {
+            if (dictionary.TryGetValue(key, out V existingValue))
+            {
+                return existingValue;
+            }
+
+            dictionary.Add(key, value);
+            return value;
+        }
+    }
+}