A simple ability
In the previous section, we applied a Gameplay Effect manually. Usually, you would use an Ability to orchestrate the application of Gameplay Effects, as well as performing/timing animations, etc. The Ability is the cornerstone of the Gameplay Ability System, and is the most complex component. Since Abilities are highly game-specific, these will require coding to develop as appropriate.
An ability references various other assets, which at a minimum include:
- Cooldown Gameplay Effect
- Cost Gameplay Effect
- Gameplay Effect(s) to be applied
- Gameplay Tags
For the first part of this tutorial, we'll create a new ability that applies the buff we created in the last section. We'll use the Simple Ability for this.
To keep assets organised, we'll store abilities in a Assets/Abilities/[Ability Name] folder structure. We'll call this ability Health Buff, so begin by creating a new folder called Assets/Abilities/Health Buff. Create a new Simple Ability via the Assets | Create | Gameplay Ability System | Abilities | Simple Ability menu, and call it Health Buff. Set the Ability Name to Health Buff in the Inspector.
Now, we need to create the Cooldown Gameplay Effects associated with our ability. Create a new Gameplay Effect via the Assets | Create | Gameplay Ability System | Gameplay Effect Definition menu, and call it Health Buff Cooldown Gameplay Effect. We'll set this Gameplay Effect to have a duration of 2 seconds, with no modifiers.
Create a new Gameplay Tag (via Assets | Create | Gameplay Ability System | Tag menu) called Health Buff.Cooldown and assign it to the Gameplay Effect Asset Tag and add it to the Granted Tags list.
Assign this Gameplay Effect to the Cooldown property of the Ability in the inspector.
Create a new Gameplay Effect, setting the Duration Policy to Instant, and a new Gameplay Tag for the Asset Tag property:
Prior to casting an ability, a resource check is done based on the Cost. Since the Health attribute starts at 0, we would not be able to activate the ability. For this example, we can get around this by leaving the Modifiers list empty.
Assign this Gameplay Effect to the Cost property of the Ability in the inspector.
The Simple Ability accepts a single Gameplay Effect to apply when the ability is activated. Assign the Gameplay Effect created in the previous section (Health Buff Gameplay Effect).
Create a new Gameplay Tag (via Assets | Create | Gameplay Ability System | Tag menu), and call it Health Buff. Assign this Gameplay Tag to the Ability Tags/Ability Tag property for the Health Buff ability.
The ability is now properly set-up, and should look like:
Activating an ability is a two-step process:
- Create the Ability Spec, which is a unique instance of the ability
- Activate the ability using a character. Since an ability can span multiple frames (e.g. projectile travelling to target), the activation method is a
Coroutine, andStartCoroutine()must be used.
Assuming the AbilitySystemCharacter is called abilitySystemCharacter, and the AbstractAbilityScriptableObject is called ability:
AbstractAbilitySpec abilitySpec = ability.CreateSpec(abilitySystemCharacter);
StartCoroutine(abilitySpec.TryActivateAbility());In the previous example, we noted that the Gameplay Effect could be applied endlessly, unless we modified the Granted Tags and Application Required Tags / Ignore Tags lists. We'll now empty the Application Required Tags / Ignore Tags list.
When you activate the ability, you should now see the Health attribute increase. The ability cannot be activated more than once every 2 seconds, and the effect of the ability (the increase in health) stays for 5 seconds, and then reverts.
By coordinating the use of Gameplay Effects, Gameplay Tags and Abilities, you can create complex abilities.