[LYN-3717] When pulling in an actor FBX, two entities are spawned & [ATOM-15258] Clicking and Dragging fbx file into viewport produces 2 entities (#1392)

* [LYN-3717] When pulling in an actor FBX, two entities are spawned & [ATOM-15258] Clicking and Dragging fbx file into viewport produces 2 entities
* Added another operation to the CanSpawnEntityForProduct that checks the other products and can veto the creation process.
* The model product will not create an entity in case there is already an actor exported, which prevents the issue reported by two different teams/users.

Code/Framework/AzCore/AzCore/Asset/AssetTypeInfoBus.h

@@ -57,7 +57,13 @@ namespace AZ
         //! Determines if a component can be created from the asset type
         //! This will be called before attempting to create a component from an asset (drag&drop, etc)
         //! You can use this to filter by subIds or do your own validation here if needed
-        virtual bool CanCreateComponent(const AZ::Data::AssetId& /*assetId*/) const { return true; }
+        virtual bool CanCreateComponent([[maybe_unused]] const AZ::Data::AssetId& assetId) const { return true; }
+
+        //! Determines if other products conflict with the given one when multiple are generated from a source asset.
+        //! This will be called before attempting to create a component from an asset (drag&drop, etc)
+        //! You can use this to filter by conflicting product types or in case you want to skip for UX reasons.
+        //! @param[in] productAssetTypes Asset types of all generated products, including the one for our given type in this bus.
+        virtual bool HasConflictingProducts([[maybe_unused]] const AZStd::vector<AZ::Data::AssetType>& productAssetTypes) const { return false; }
     };
 
     using AssetTypeInfoBus = AZ::EBus<AssetTypeInfo>;

Code/Sandbox/Editor/AzAssetBrowser/AzAssetBrowserRequestHandler.cpp

@@ -56,7 +56,8 @@ namespace AzAssetBrowserRequestHandlerPrivate
     using namespace AzToolsFramework;
     using namespace AzToolsFramework::AssetBrowser;
     // return true ONLY if we can handle the drop request in the viewport.
-    bool CanSpawnEntityForProduct(const ProductAssetBrowserEntry* product)
+    bool CanSpawnEntityForProduct(const ProductAssetBrowserEntry* product,
+        AZStd::optional<const AZStd::vector<AZ::Data::AssetType>> optionalProductAssetTypes = AZStd::nullopt)
     {
         if (!product)
         {
@@ -70,7 +71,6 @@ namespace AzAssetBrowserRequestHandlerPrivate
 
         bool canCreateComponent = false;
         AZ::AssetTypeInfoBus::EventResult(canCreateComponent, product->GetAssetType(), &AZ::AssetTypeInfo::CanCreateComponent, product->GetAssetId());
-
         if (!canCreateComponent)
         {
             return false;
@@ -78,16 +78,25 @@ namespace AzAssetBrowserRequestHandlerPrivate
 
         AZ::Uuid componentTypeId = AZ::Uuid::CreateNull();
         AZ::AssetTypeInfoBus::EventResult(componentTypeId, product->GetAssetType(), &AZ::AssetTypeInfo::GetComponentTypeId);
-
-        if (!componentTypeId.IsNull())
+        if (componentTypeId.IsNull())
         {
             // we have a component type that handles this asset.
-            return true;
+            return false;
+        }
+
+        if (optionalProductAssetTypes.has_value())
+        {
+            bool hasConflictingProducts = false;
+            AZ::AssetTypeInfoBus::EventResult(hasConflictingProducts, product->GetAssetType(), &AZ::AssetTypeInfo::HasConflictingProducts, optionalProductAssetTypes.value());
+            if (hasConflictingProducts)
+            {
+                return false;
+            }
         }
 
         // additional operations can be added here.
 
-        return false;
+        return true;
     }
 
     void SpawnEntityAtPoint(const ProductAssetBrowserEntry* product, AzQtComponents::ViewportDragContext* viewportDragContext, EntityIdList& spawnList, AzFramework::SliceInstantiationTicket& spawnTicket)
@@ -511,9 +520,16 @@ void AzAssetBrowserRequestHandler::Drop(QDropEvent* event, AzQtComponents::DragA
     }
 
     // Handle products
+    AZStd::vector<AZ::Data::AssetType> productAssetTypes;
+    productAssetTypes.reserve(products.size());
+    for (const AzToolsFramework::AssetBrowser::ProductAssetBrowserEntry* entry : products)
+    {
+        productAssetTypes.emplace_back(entry->GetAssetType());
+    }
+
     for (const ProductAssetBrowserEntry* product : products)
     {
-        if (CanSpawnEntityForProduct(product))
+        if (CanSpawnEntityForProduct(product, productAssetTypes))
         {
             SpawnEntityAtPoint(product, viewportDragContext, spawnedEntities, spawnTicket);
         }

Gems/Atom/RPI/Code/Include/Atom/RPI.Reflect/Model/ModelAsset.h

@@ -103,10 +103,14 @@ namespace AZ
             AZStd::size_t CalculateTriangleCount() const;
         };
 
-        class ModelAssetHandler : public AssetHandler<ModelAsset>
+        class ModelAssetHandler
+            : public AssetHandler<ModelAsset>
         {
         public:
             AZ_RTTI(ModelAssetHandler, "{993B8CE3-1BBF-4712-84A0-285DB9AE808F}", AssetHandler<ModelAsset>);
+
+            // AZ::AssetTypeInfoBus::Handler overrides
+            bool HasConflictingProducts(const AZStd::vector<AZ::Data::AssetType>& productAssetTypes) const override;
         };
     } //namespace RPI
 } // namespace AZ

Gems/Atom/RPI/Code/Source/RPI.Reflect/Model/ModelAsset.cpp

@@ -315,5 +315,26 @@ namespace AZ
 
             return modelTriangleCount;
         }
-    } //namespace RPI
+
+        bool ModelAssetHandler::HasConflictingProducts(const AZStd::vector<AZ::Data::AssetType>& productAssetTypes) const
+        {
+            size_t modelAssetCount = 0;
+            size_t actorAssetCount = 0;
+            for (const AZ::Data::AssetType& assetType : productAssetTypes)
+            {
+                if (assetType == azrtti_typeid<ModelAsset>())
+                {
+                    modelAssetCount++;
+                }
+                else if (assetType == AZ::Data::AssetType("{F67CC648-EA51-464C-9F5D-4A9CE41A7F86}")) // ActorAsset
+                {
+                    actorAssetCount++;
+                }
+            }
+
+            // When dropping a well-defined character, consisting of a mesh and a skeleton/actor,
+            // do not create an entity with a mesh component.
+            return modelAssetCount == 1 && actorAssetCount == 1;
+        }
+    } // namespace RPI
 } // namespace AZ