Changing an animation is as easy as replacing the clip within the Animator Controller's state or blend tree. There is one additional step necessary in order to get the used animation to work. When the character uses an item (such as firing a weapon), the controller needs to know when the actual used event takes place. This prevents the character from using the item too early. This notification is sent through Animation Events. If we look at one of the used animations, such as the Assault Rifle Attack, we'll see that there is an animation event setup (indicated by the vertical white line near 1:00 on the timeline):
Opening this event we'll see:
These parameters let the controller know that the character has used an item. The Int parameter indicates the type of item used. A value of 0 indicates a primary item, 1 indicates a secondary item, and 2 indicates a dual wield item.
<- Replace the Aim Animation