Customizing EMotionFX Objects

The EMotion FX API supports registering custom object types, including state machine nodes, blend tree nodes, transitions, and conditions. You can define custom object types in your game code or a custom gem. This allows you to have granular control of the O3DE animation system.

Registering Custom Objects

Before registering custom objects, activate the EMotion FX SystemComponent to ensure the EMotion FX runtime is initialized correctly. Then use an EBus call to the EMotionFXRequestBus::Events::RegisterAnimGraphObjectType method. You can ensure that EMotion FX runtime is activated by registering your custom node from a component that has a dependency on EmotionFXAnimationService. You do not need to manually instantiate the EMotion FX SystemComponent and call Activate; component dependencies handle these tasks.

To register your custom node

1. In your custom gem or game project code, define your subclass of EMotionFX::AnimGraphObject.

2. Create a subclass of AZ::Component.

3. In your component’s GetDependentServices() method, add the dependency to EmotionFXAnimationService:

   dependent.push_back(AZ_CRC("EmotionFXAnimationService", 0x3f8a6369));
   

4. In your component’s Activate() method, register your node type:

   EmotionFXAnimation::EMotionFXRequestBus::Broadcast(
     &EmotionFXAnimation::EMotionFXRequestBus::Events::RegisterAnimGraphNodeType,
       MyCustomNode::Create(nullptr)
   );
   

Implementing AnimGraphObject Subclasses

AnimGraphObject is the base class for all objects in the animation graph. The constructor on the base class is protected; instead, objects are instantiated with the Create() method. The O3DE animation system (EMotion FX) uses an instance of AnimGraphObject to create other instances by calling the Clone() method.

Each AnimGraphObject subclass has a unique type ID that is used to serialize an object to and unserialize an object from an .animgraph file. You use a public anonymous enum with a TYPE_ID member to declare the type ID for an object.

When implementing an AnimGraphObject subclass, you must define the following methods: