feat: add relative/absolute particle position mode

close #205

Scripts/Editor/UIParticleEditor.cs

@@ -62,6 +62,7 @@ namespace Coffee.UIExtensions
         private SerializedProperty m_MeshSharing;
         private SerializedProperty m_GroupId;
         private SerializedProperty m_GroupMaxId;
+        private SerializedProperty m_AbsoluteMode;
 
 
         private ReorderableList _ro;
@@ -150,6 +151,7 @@ namespace Coffee.UIExtensions
             m_MeshSharing = serializedObject.FindProperty("m_MeshSharing");
             m_GroupId = serializedObject.FindProperty("m_GroupId");
             m_GroupMaxId = serializedObject.FindProperty("m_GroupMaxId");
+            m_AbsoluteMode = serializedObject.FindProperty("m_AbsoluteMode");
 
             var sp = serializedObject.FindProperty("m_Particles");
             _ro = new ReorderableList(sp.serializedObject, sp, true, true, true, true);
@@ -265,6 +267,9 @@ namespace Coffee.UIExtensions
                 }
             }
 
+            // Absolute Mode
+            EditorGUILayout.PropertyField(m_AbsoluteMode);
+
             // Target ParticleSystems.
             _ro.DoLayoutList();
 

Scripts/UIParticle.cs

@@ -54,6 +54,10 @@ namespace Coffee.UIExtensions
         [SerializeField]
         private int m_GroupMaxId = 0;
 
+        [SerializeField]
+        [Tooltip("The particles will be emitted at the ParticleSystem position.\nMove the UIParticle/ParticleSystem to move the particle.")]
+        private bool m_AbsoluteMode = false;
+
         private List<UIParticleRenderer> m_Renderers = new List<UIParticleRenderer>();
 
 #if !SERIALIZE_FIELD_MASKABLE
@@ -112,6 +116,17 @@ namespace Coffee.UIExtensions
             }
         }
 
+        /// <summary>
+        /// Absolute particle position mode.
+        /// The particles will be emitted at the ParticleSystem position.
+        /// Move the UIParticle/ParticleSystem to move the particle.
+        /// </summary>
+        public bool absoluteMode
+        {
+            get { return m_AbsoluteMode; }
+            set { m_AbsoluteMode = value; }
+        }
+
         internal bool useMeshSharing
         {
             get { return m_MeshSharing != MeshSharing.None; }

Scripts/UIParticleRenderer.cs

@@ -249,7 +249,15 @@ namespace Coffee.UIExtensions
             Profiler.BeginSample("[UIParticleRenderer] Combine Mesh");
             if (_parent.canSimulate)
             {
-                s_CombineInstances[0].transform = canvasRenderer.transform.worldToLocalMatrix * GetWorldMatrix(psPos, scale);
+                if (_parent.absoluteMode)
+                {
+                    s_CombineInstances[0].transform = canvasRenderer.transform.worldToLocalMatrix * GetWorldMatrix(psPos, scale);
+                }
+                else
+                {
+                    var diff = _particleSystem.transform.position - _parent.transform.position;
+                    s_CombineInstances[0].transform = canvasRenderer.transform.worldToLocalMatrix * Matrix4x4.Translate(diff.GetScaled(scale - Vector3.one)) * GetWorldMatrix(psPos, scale);
+                }
                 workerMesh.CombineMeshes(s_CombineInstances, true, true);
 
                 workerMesh.RecalculateBounds();