feat: Combine baked meshes to improve performance

Packages/UIParticle/Scripts/MeshHelper.cs

@@ -0,0 +1,85 @@
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace Coffee.UIExtensions
+{
+    internal static class MeshHelper
+    {
+        private static CombineInstance[] s_CombineInstances;
+        private static int s_CurrentIndex;
+        static readonly List<Color32> s_Colors = new List<Color32>();
+        private static int s_RefCount;
+
+        public static void Register()
+        {
+            if (0 < s_RefCount++) return;
+            s_CombineInstances = new CombineInstance[2];
+        }
+
+        public static void Unregister()
+        {
+            s_RefCount--;
+
+            if (0 < s_RefCount || s_CombineInstances == null) return;
+
+            for (var i = 0; i < s_CombineInstances.Length; i++)
+            {
+#if UNITY_EDITOR
+                if (!Application.isPlaying)
+                    Object.DestroyImmediate(s_CombineInstances[i].mesh);
+                else
+#endif
+                {
+                    Object.Destroy(s_CombineInstances[i].mesh);
+                }
+            }
+
+            s_CombineInstances = null;
+        }
+
+        public static Mesh GetTemporaryMesh()
+        {
+            return s_CombineInstances[s_CurrentIndex++].mesh;
+        }
+
+        public static void Clear()
+        {
+            s_CurrentIndex = 0;
+            for (var i = 0; i < s_CombineInstances.Length; i++)
+            {
+                if (!s_CombineInstances[i].mesh)
+                {
+                    var mesh = new Mesh();
+                    mesh.MarkDynamic();
+                    s_CombineInstances[i].mesh = mesh;
+                }
+                else
+                {
+                    s_CombineInstances[i].mesh.Clear(false);
+                }
+            }
+        }
+
+        public static void CombineMesh(Mesh result, Matrix4x4 transform)
+        {
+            if (!result || s_CurrentIndex == 0) return;
+
+            for (var i = 0; i < 2; i++)
+                s_CombineInstances[i].transform = transform;
+
+            result.CombineMeshes(s_CombineInstances, false, true);
+            result.RecalculateBounds();
+        }
+
+        public static void ModifyColorSpaceToLinear(this Mesh self)
+        {
+            self.GetColors(s_Colors);
+
+            for (var i = 0; i < s_Colors.Count; i++)
+                s_Colors[i] = ((Color) s_Colors[i]).gamma;
+
+            self.SetColors(s_Colors);
+            s_Colors.Clear();
+        }
+    }
+}