Legacy Documentation: Version 2017.2 (Go to current version)
State Machine Transitions
Sub-State Machines
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State Machine Behaviours

A State Machine Behaviour is a special class of script. In a similar way to attaching regular Unity scripts (MonoBehaviours) to individual GameObjects, you can attach a StateMachineBehaviour script to an individual state within a state machine. This allows you to write code that will execute when the state machine enters, exits or remains within a particular state. This means you do not have to write your own logic to test for and detect changes in state.

A few examples for the use of this feature might be to:

  • Play sounds as states are entered or exited
  • Perform certain tests (eg, ground detection) only when in appropriate states
  • Activate and control special effects associated with specific states

State Machine Behaviours can be created and added to states in a very similar way to the way you would create and add scripts to GameObjects. Select a state in your state machine, and then in the inspector use the “Add Behaviour” button to select an existing StateMachineBehaviour or create a new one.

A state machine with a behaviour attached to the Grounded state
A state machine with a behaviour attached to the “Grounded” state

State Machine Behaviour scripts have access to a number of events that are called when the Animator enters, updates and exits different states (or sub-state machines). There are also events which allow you to handle the Root motion and Inverse Kinematics calls.

For more information see the State Machine Behaviour script reference.

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State Machine Transitions
Sub-State Machines