fix: when using mesh sharing, the `Transform.scale` of the primary UIParticle affects the replicas.

close #333

NOTE: This fix may cause changes in the rendering of existing UIParticles.

Packages/src/Runtime/UIParticle.cs

@@ -586,7 +586,7 @@ namespace Coffee.UIExtensions
             }
         }
 
-        internal void UpdateTransformScale()
+        internal void UpdateTransformScale(Vector3 ratio)
         {
             _tracker.Clear();
             canvasScale = canvas.rootCanvas.transform.localScale.Inverse();
@@ -610,7 +610,7 @@ namespace Coffee.UIExtensions
             }
 
             _tracker.Add(this, rectTransform, DrivenTransformProperties.Scale);
-            var newScale = parentScale.Inverse();
+            var newScale = parentScale.GetScaled(ratio).Inverse();
             if (currentScale != newScale)
             {
                 transform.localScale = newScale;

Packages/src/Runtime/UIParticleUpdater.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using Coffee.UIParticleExtensions;
 using UnityEditor;
 using UnityEngine;
 
@@ -8,7 +9,7 @@ namespace Coffee.UIExtensions
     {
         private static readonly List<UIParticle> s_ActiveParticles = new List<UIParticle>();
         private static readonly List<UIParticleAttractor> s_ActiveAttractors = new List<UIParticleAttractor>();
-        private static readonly HashSet<int> s_UpdatedGroupIds = new HashSet<int>();
+        private static readonly Dictionary<int, Vector3> s_GroupScales = new Dictionary<int, Vector3>();
         private static int s_FrameCount;
 
         public static int uiParticleCount => s_ActiveParticles.Count;
@@ -53,14 +54,17 @@ namespace Coffee.UIExtensions
             // Do not allow it to be called in the same frame.
             if (s_FrameCount == Time.frameCount) return;
             s_FrameCount = Time.frameCount;
+            s_GroupScales.Clear();
 
             // Simulate -> Primary
             for (var i = 0; i < s_ActiveParticles.Count; i++)
             {
+                // Process only primary UIParticles.
                 var uip = s_ActiveParticles[i];
-                if (!uip || !uip.canvas || !uip.isPrimary || !s_UpdatedGroupIds.Add(uip.groupId)) continue;
+                if (!uip || !uip.canvas || !uip.isPrimary || s_GroupScales.ContainsKey(uip.groupId)) continue;
 
-                uip.UpdateTransformScale();
+                s_GroupScales.Add(uip.groupId, uip.transform.parent.lossyScale);
+                uip.UpdateTransformScale(Vector3.one);
                 uip.UpdateRenderers();
             }
 
@@ -70,20 +74,31 @@ namespace Coffee.UIExtensions
                 var uip = s_ActiveParticles[i];
                 if (!uip || !uip.canvas) continue;
 
-                uip.UpdateTransformScale();
+                // Case 1: Not using mesh sharing.
-
                 if (!uip.useMeshSharing)
                 {
+                    uip.UpdateTransformScale(Vector3.one);
                     uip.UpdateRenderers();
                 }
-                else if (s_UpdatedGroupIds.Add(uip.groupId))
+                // Case 2: Using mesh sharing as primary.
+                else if (!s_GroupScales.TryGetValue(uip.groupId, out var groupScale))
                 {
+                    s_GroupScales.Add(uip.groupId, uip.transform.parent.lossyScale);
+                    uip.UpdateTransformScale(Vector3.one);
                     uip.UpdateRenderers();
                 }
+                // Case 3: Using mesh sharing as replica. (Only scaling)
+                else
+                {
+                    var parentScale = uip.transform.parent.lossyScale;
+                    var ratio = parentScale.IsVisible()
+                        ? groupScale.GetScaled(parentScale.Inverse())
+                        : Vector3.one;
+                    ratio = Vector3.one;
+                    uip.UpdateTransformScale(ratio);
+                }
             }
 
-            s_UpdatedGroupIds.Clear();
-
             // Attract
             for (var i = 0; i < s_ActiveAttractors.Count; i++)
             {