Reparenting objects maintain world transforms

Assets/Editor/Layouts/UserLayout.ini

@@ -10,7 +10,7 @@ Collapsed=0
 
 [Window][Hierarchy Panel]
 Pos=0,142
-Size=571,918
+Size=349,918
 Collapsed=0
 DockId=0x00000004,0
 
@@ -20,29 +20,29 @@ Size=400,400
 Collapsed=0
 
 [Window][Inspector]
-Pos=1649,48
+Pos=1483,48
-Size=271,1012
+Size=437,1012
 Collapsed=0
 DockId=0x00000006,0
 
 [Window][Profiler]
 Pos=0,48
-Size=571,92
+Size=349,92
 Collapsed=0
 DockId=0x00000003,0
 
 [Window][Viewport]
-Pos=573,48
+Pos=351,48
-Size=1074,1012
+Size=1130,1012
 Collapsed=0
 DockId=0x00000002,0
 
 [Docking][Data]
 DockSpace       ID=0xC5C9B8AB Window=0xBE4044E9 Pos=8,79 Size=1920,1012 Split=X
-  DockNode      ID=0x00000005 Parent=0xC5C9B8AB SizeRef=1992,1036 Split=X
+  DockNode      ID=0x00000005 Parent=0xC5C9B8AB SizeRef=1481,1036 Split=X
-    DockNode    ID=0x00000001 Parent=0x00000005 SizeRef=571,1036 Split=Y Selected=0x1E6EB881
+    DockNode    ID=0x00000001 Parent=0x00000005 SizeRef=349,1036 Split=Y Selected=0x1E6EB881
       DockNode  ID=0x00000003 Parent=0x00000001 SizeRef=225,94 Selected=0x1E6EB881
       DockNode  ID=0x00000004 Parent=0x00000001 SizeRef=225,940 Selected=0xE096E5AE
-    DockNode    ID=0x00000002 Parent=0x00000005 SizeRef=1074,1036 CentralNode=1 Selected=0x13926F0B
+    DockNode    ID=0x00000002 Parent=0x00000005 SizeRef=1130,1036 CentralNode=1 Selected=0x13926F0B
-  DockNode      ID=0x00000006 Parent=0xC5C9B8AB SizeRef=271,1036 Selected=0xE7039252
+  DockNode      ID=0x00000006 Parent=0xC5C9B8AB SizeRef=437,1036 Selected=0xE7039252
 

SHADE_Application/src/Scenes/SBTestScene.cpp

@@ -77,9 +77,9 @@ namespace Sandbox
     customMat->SetProperty("data.alpha", 0.1f);
 
     // Create Stress Test Objects
-    static const SHVec3 TEST_OBJ_SCALE = SHVec3::One * 0.5f;
+    static const SHVec3 TEST_OBJ_SCALE = SHVec3::One;
-    constexpr int NUM_ROWS = 10;
+    constexpr int NUM_ROWS = 2;
-    constexpr int NUM_COLS = 10;
+    constexpr int NUM_COLS = 1;
     static const SHVec3 TEST_OBJ_SPACING = { 0.1f, 0.1f, 0.1f };
     static const SHVec3 TEST_OBJ_START_POS = { -(NUM_COLS / 2 * TEST_OBJ_SPACING.x) + 1.0f, -2.0f, -1.0f };
 

SHADE_Engine/src/Math/Transform/SHTransformSystem.cpp

@@ -17,7 +17,6 @@
 #include "Scene/SHSceneManager.h"
 #include "ECS_Base/Managers/SHComponentManager.h"
 #include "ECS_Base/Managers/SHEntityManager.h"
-#include "Tools/SHException.h"
 
 namespace SHADE
 {
@@ -47,7 +46,9 @@ namespace SHADE
 
   void SHTransformSystem::Init()
   {
-
+    std::shared_ptr thisReceiver { std::make_shared<SHEventReceiverSpec<SHTransformSystem>>(this, &SHTransformSystem::ChangeParent) };
+    ReceiverPtr receiver = std::dynamic_pointer_cast<SHEventReceiver>(thisReceiver);
+    SHEventManager::SubscribeTo(SH_SCENEGRAPH_CHANGE_PARENT_EVENT, receiver);
   }
 
   void SHTransformSystem::Exit()
@@ -59,6 +60,44 @@ namespace SHADE
   /* Private Function Member Definitions                                               */
   /*-----------------------------------------------------------------------------------*/
 
+  SHEventHandle SHTransformSystem::ChangeParent(SHEventPtr changeParentEvent)
+  {
+    const auto& eventData = reinterpret_cast<const SHEventSpec<SHSceneGraphChangeParentEvent>*>(changeParentEvent.get());
+
+    // Get Current Respective Components
+    auto* tf            = SHComponentManager::GetComponent<SHTransformComponent>(eventData->data->entityID);
+    const auto* PARENT  = SHComponentManager::GetComponent_s<SHTransformComponent>(eventData->data->newParentID);
+
+    // Recompute local transform and store localToWorld Matrix
+    SHMatrix localToWorld = SHMatrix::Identity; 
+    SHMatrix worldToLocal = SHMatrix::Identity;
+
+    if (PARENT != nullptr) // Not the root
+    {
+      localToWorld = PARENT->GetTRS();
+      worldToLocal = SHMatrix::Inverse(localToWorld);
+    }
+
+    // Maintain World Transform and recompute Local Transform
+
+    // Compute Local Position
+    tf->local.position = SHVec3::Transform(tf->world.position, worldToLocal);
+
+    // Compute Local Rotation
+    tf->local.rotation = tf->world.rotation;
+    if (PARENT)
+      tf->local.rotation -= PARENT->GetLocalRotation();
+
+    // Compute Local Scale
+    tf->local.scale = tf->world.scale;
+    if (PARENT)
+        tf->local.scale /= PARENT->GetLocalScale();
+
+    tf->local.trs = localToWorld;
+
+    return eventData->handle;
+  }
+
   void SHTransformSystem::UpdateEntity(const SHSceneNode* node)
   {
     const auto* NODE_TRANSFORM = SHComponentManager::GetComponent_s<SHTransformComponent>(node->GetEntityID());

SHADE_Engine/src/Math/Transform/SHTransformSystem.h

@@ -84,6 +84,8 @@ namespace SHADE
     /* Function Members                                                                */
     /*---------------------------------------------------------------------------------*/
 
+    SHEventHandle ChangeParent    (SHEventPtr changeParentEvent);
+
     static void   UpdateEntity    (const SHSceneNode* node);
     static void   UpdateTransform (SHTransformComponent& tf, const SHTransformComponent* parent = nullptr);
   };

SHADE_Engine/src/Scene/SHSceneGraph.cpp

@@ -367,8 +367,9 @@ namespace SHADE
 
     const SHSceneGraphChangeParentEvent EVENT_DATA
     {
-      .oldParentID = NODE_ITER->second->GetParent()->GetEntityID(),
+      .entityID     = entityID
-      .newParentID = parent->GetEntityID()
+    , .oldParentID  = NODE_ITER->second->GetParent()->GetEntityID()
+    , .newParentID  = parent ? parent->GetEntityID() : root->GetEntityID()
     };
 
     if (parent == nullptr)
@@ -412,8 +413,9 @@ namespace SHADE
 
     const SHSceneGraphChangeParentEvent EVENT_DATA
     {
-      .oldParentID = NODE_ITER->second->GetParent()->GetEntityID(),
+      .entityID     = entityID
-      .newParentID = parent
+    , .oldParentID  = NODE_ITER->second->GetParent()->GetEntityID()
+    , .newParentID  = parent
     };
 
     SHSceneNode* currentNode = NODE_ITER->second;

SHADE_Engine/src/Scene/SHSceneGraph.h

@@ -163,6 +163,7 @@ namespace SHADE
 
   struct SHSceneGraphChangeParentEvent
   {
+    EntityID entityID;
     EntityID oldParentID;
     EntityID newParentID;
   };