StateMachineBehaviour
StateMachineBehaviour is a component that can be added to a state machine state. It's the base class any script on a state must derive from.
Read time 7 minutesLast updated 2 days ago
Definition
- Type: Class
- Namespace: UnityEngine
- Assembly: UnityEngine.AnimationModule
- Inherits from: ScriptableObject
public abstract class StateMachineBehaviour : ScriptableObject
Remarks
State machines can have up to three different active states at the same time: the current state, the next state and the interrupted state.
The state machine always has a current state. When the state machine transitions to a new state, a "next state" is added. Once the transition is complete, the current state is terminated and the next state becomes the new current state.
If an ongoing transition is interrupted by a transition to a new state, then the next state becomes the interrupted state and the state targeted by the new transition is now the next state. The current state will remain the same until all interrupted transitions have completed. Once the last transition is complete and there are no more interruptions, the current and interrupted states are terminated, and the next state becomes the new current state.
StateMachineBehaviour has some predefined state-related messages that you can implement:OnStateEnter, OnStateExit, OnStateIK, OnStateMove, OnStateUpdate.
Whenever appropriate, these messages will be invoked for the active states mentioned above in the following order: current state, then interrupted state, then next state.
See the description of each message for more information.
StateMachineBehaviour also has some predefined messages related to transitions in and out of state machines:
These are invoked whenever a state machine transition is taken.
Layer considerations:
If an AnimatorController contains sychronized layers, the messages may be invoked multiple times for a single state. In that situation, the messages will be invoked once per synchronized layer that contains the state, in ascending order.
Additional considerations:
By default the Animator instantiates a new instance of each behaviour defined in the controller. If you wish to share behaviour instances, use the class attribute SharedBetweenAnimatorsAttribute to control how behaviours are instantiated.
Examples
using UnityEngine;public class AttackBehaviour : StateMachineBehaviour{ public GameObject particle; public float radius; public float power; protected GameObject clone; override public void OnStateEnter(Animator animator, AnimatorStateInfo stateInfo, int layerIndex) { clone = Instantiate(particle, animator.rootPosition, Quaternion.identity) as GameObject; Rigidbody rb = clone.GetComponent<Rigidbody>(); rb.AddExplosionForce(power, animator.rootPosition, radius, 3.0f); } override public void OnStateExit(Animator animator, AnimatorStateInfo stateInfo, int layerIndex) { Destroy(clone); } override public void OnStateUpdate(Animator animator, AnimatorStateInfo stateInfo, int layerIndex) { Debug.Log("On Attack Update "); } override public void OnStateMove(Animator animator, AnimatorStateInfo stateInfo, int layerIndex) { Debug.Log("On Attack Move "); } override public void OnStateIK(Animator animator, AnimatorStateInfo stateInfo, int layerIndex) { Debug.Log("On Attack IK "); }}
Methods
Method | Description |
|---|---|
| OnStateEnter | Invoked on the first update frame when a state machine evaluates this state. Implement this message to react to a new state starting. |
| OnStateExit | Invoked on the last update frame when a state machine evaluates this state. Implement this message to react to a state ending. |
| OnStateIK | Invoked during the Animator IK pass. Implement this message to modify the result of the animation after the evaluation of the state machine on a state by state basis. |
| OnStateMachineEnter | Invoked on the first update frame when taking a transition into a state machine. Implement this message to influence the entry transition into the sub-state machine. |
| OnStateMachineExit | Invoked on the last update frame when taking a transition out of a StateMachine. Implement this message to influence the exit transition out of the sub-state machine |
| OnStateMove | Invoked during the Animator Root Motion pass. Implement this message to modify the result of the animation root motion on a state by state basis. |
| OnStateUpdate | Invoked on each update frame except for the first and last frame. Implement this message to execute custom logic on a state by state basis. |
Inheritance
Operators
Operator | Description |
|---|---|
| operator == | Compares two object references to see if they refer to the same object. |
| bool | Determines whether the object exists. |
| operator != | Compares if two objects refer to a different object. |