Unity - Scripting API: Animator.CrossFade

public function CrossFade(stateName: string, transitionDuration: float, layer: int = -1, normalizedTime: float = float.NegativeInfinity): void;

public function CrossFade(stateNameHash: int, transitionDuration: float, layer: int = -1, normalizedTime: float = float.NegativeInfinity): void;

Parameters

stateName	The name of the destination state.
transitionDuration	The duration of the transition. Value is in source state normalized time.
normalizedTime	Start time of the current destination state. Value is in source state normalized time, should be between 0 and 1.
layer	Layer index containing the destination state.
stateNameHash	State hash of the destination state.

Create a dynamic transition between the current state and the destination state.

Both state as to be on the same layer.

You cannot change the current state on a synchronized layer, you need to change it on the referenced layer.