reworked mesh decimation yes

LightlessSync/ThirdParty/Nanomesh/Algo/Decimation/SceneDecimator.cs

@@ -0,0 +1,72 @@
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Nanomesh
+{
+    public class SceneDecimator
+    {
+        private class ModifierAndOccurrences
+        {
+            public int occurrences = 1;
+            public DecimateModifier modifier = new DecimateModifier();
+        }
+
+        private Dictionary<ConnectedMesh, ModifierAndOccurrences> _modifiers;
+
+        public void Initialize(IEnumerable<ConnectedMesh> meshes)
+        {
+            _modifiers = new Dictionary<ConnectedMesh, ModifierAndOccurrences>();
+
+            foreach (ConnectedMesh mesh in meshes)
+            {
+                ModifierAndOccurrences modifier;
+                if (_modifiers.ContainsKey(mesh))
+                {
+                    modifier = _modifiers[mesh];
+                    modifier.occurrences++;
+                }
+                else
+                {
+                    _modifiers.Add(mesh, modifier = new ModifierAndOccurrences());
+                    //System.Console.WriteLine($"Faces:{mesh.FaceCount}");
+                    modifier.modifier.Initialize(mesh);
+                }
+
+                _faceCount += mesh.FaceCount;
+            }
+
+            _initalFaceCount = _faceCount;
+        }
+
+        private int _faceCount;
+        private int _initalFaceCount;
+
+        public void DecimateToRatio(float targetTriangleRatio)
+        {
+            targetTriangleRatio = MathF.Clamp(targetTriangleRatio, 0f, 1f);
+            DecimateToPolycount((int)MathF.Round(targetTriangleRatio * _initalFaceCount));
+        }
+
+        public void DecimatePolycount(int polycount)
+        {
+            DecimateToPolycount((int)MathF.Round(_initalFaceCount - polycount));
+        }
+
+        public void DecimateToPolycount(int targetTriangleCount)
+        {
+            //System.Console.WriteLine($"Faces:{_faceCount} Target:{targetTriangleCount}");
+            while (_faceCount > targetTriangleCount)
+            {
+                KeyValuePair<ConnectedMesh, ModifierAndOccurrences> pair = _modifiers.OrderBy(x => x.Value.modifier.GetMinimumError()).First();
+
+                int facesBefore = pair.Key.FaceCount;
+                pair.Value.modifier.Iterate();
+
+                if (facesBefore == pair.Key.FaceCount)
+                    break; // Exit !
+
+                _faceCount -= (facesBefore - pair.Key.FaceCount) * pair.Value.occurrences;
+            }
+        }
+    }
+}