Getting Started

This tutorial is available on youtube

Verify Installation

1. Open a new project

2. Make sure Plugin content is visible

   Content Drawer / Settings / Show Engine Content [X] Content Drawer / Settings / Show Plugins Content [X]

3. Load Example Map

   Plugins / GKAbility Content / Example / GKAbility

4. Set Game Mode Override

   WorldSettings / GameMode Override / GKAbility_GameMode

Setup

1. Create inputs use an EnhancedInputContext

   • Gamekit provided a few predefine action you can reuse including ConfirmTarget & CancelTarget input/Action

2. Create a new enum with the same action/input names (see EGK_MOBA_AbilityInputID as an example)

3. Create a Character from GKCharacterBase

4. Extend the On Setup Player Input Component event, use to register your input to the ability system component (See AGKCharacterBase::BindAbilityActivationFromInputEnum())

   Warning

   FGKGameplayAbilityInputBinds::CancelCommand and FGKGameplayAbilityInputBinds::ConfirmCommand are the named defined in the input’s project setting NOT the enum name.

5. You are ready to grant abilities using AGKCharacterBase::GrantAbility() In Gamekit abilities are granted to a character for a given slot, each ability populates a slot. Slots can then be assigned an input. Gamekit defines 22 default slots (6 Skills, 8 Items, 7 Basic Abilities). Under the hood slots are simple integer, users can add as many slots as they want.

   Note

   Granting ablities can only be done by the authority

6. During Gameplay, you can press inputs and the abilities will activate.

Example

• ‘Legacy’ Player Input

• Enhanced Player Input

Creating Abilities

• Create a new DataTable using the GKAbilityStatic struct

• Insert a row, give the row a name (the row name is used to generate the ability asset)

• Click the generate button

Warning

Python Editor Scripting plugin needs to be enabled & configured

GameTags

Gametags are used to mark the current state of a player/ability/effect, it is used to control transition between different states. It is the core of the gameplay ability system, some effects are exclusively implemented through gameplaytags.

For example, Stun, Silences, Roots are all gameplay effects that simply prevent the character from using certain abilities, they can all be implemented using gameplaytag alone.

Gamekit automatically defines base gametags for its abilities.

• Ability: use to tag abilities

  • Exclusive: Used to prevent activation of multiple abilities witht the Exclusive tag

  • Move: Used to tag abilities performing movement operation

  • Passive: tag passive abilities

• Animation: used to tag animation

  • CastPoint: Tag is sent when the animation reach the point where projectile/effect should be spawned.

• Cooldown: used to tag cooldowns

  • Prevents the same ability from being casted all the time

• Buff: Improves the effectiveness of a character

  • Immunity: protects against debuff and disables

  • Armor increase

  • Damage

  • Health bonus

  • Haste: increase movement speed

  • Level: level of the buff

    • Minor

    • Medium

    • Strong

• Debuff: reduce the effectiveness of a character

  • Level: level of the debuff

    • Minor

    • Medium

    • Strong

  • Armor reduction

  • Health Penalty

  • Damage decrease

• Disable: prevent character for performing certain actions

  • Level: level of the disable

    • Minor

    • Medium

    • Strong

  • Stun: prevents movement, spell casting and item usage

  • Silence: prevents spell casting

  • Mute: prevent item usage

  • Root: prevent all movements

  • Break: disable passive abilities

  • Dead: removes all buffs, debuffs and disables

    • Death is both a disable and a dispel, on depth all active effects are removed but all actions are disabled.

  • Etheral: cannot do physical damage, cannot be damaged by physical attacks [TODO]

  • Disarmed: cannot do physical attacks [TODO]

• Dispel: removes debuff and disables

  • Level: level of the dispel

    • Minor

    • Medium

    • Strong

• Failure: used to report errors back to the users

  • Blocked: Ability is blocked by a disable

  • Cost: Resource level does not meet the ability cost

  • Missing: Ability has missing requirement

  • Network: Internal error due to networking

  • NotLearned: Ability was not learned yet

  • Cooldown: Ability is still in cooldown

  • Dead: Character is dead

• GameplayCue: used to spawn effect in reseponse to gameplay effects, all disables will have an effect so players can see it easily

  • Immunity

  • Stun

  • Silence

  • Mute

  • Root

  • Break

• Quest: used to tag objectives for the quest system

Creating GameplayEffect

• For simple gameplay effect that modify attributes you should configure the magniture to be set by caller using the tag “Ability.Magnitude”. By default, UGKGameplayAbility will populate the data from the FGKAbilityStatic data.

Define Abilities

Abilities are define inside a json file. The list of customizable properties can be found here FGKAbilityStatic. Gameplay designer can create new abilities by simply adding new abilities inside the ability data file. To create the new abilities in unreal engine you need to generate them using a python script.

1. Enable python scripting for UnrealEngine

2. Add Gamekit/Script to your python path

3. Go to Gamekit/Content/Editor/Ability_Generator right click on it and Run Editor Utility Widget. A widget should pop up with a bit “Generate Default Abilities” button

4. Click on the button, this will generate all the missing abilities

Example

{
        "Name": "Fireball",
        "AbilityKind": "Skill",
        "LocalName": "NSLOCTEXT(\"[0A85C43C484A243EF7B6B7B642AD2ACB]\", \"EC9BA0DD417F0C07C07E3DBB00F88785\", \"Fire Ball\")",
        "LocalDescription": "NSLOCTEXT(\"[0A85C43C484A243EF7B6B7B642AD2ACB]\", \"9CB2744E447BF19F751B929142E6F484\", \"Launch a roaring ball of fire in a straight line\")",
        "Icon": "Texture2D'/Gamekit/Textures/IconsSkills/fireball-red-1.fireball-red-1'",
        "MaxLevel": 4,
        "Duration": 0,
        "AbilityEffects":
        {
        },
        "Cost":
        {
                "Attribute":
                {
                        "AttributeName": "Mana",
                        "Attribute": "/Script/Gamekit.GKAttributeSet:Mana",
                        "AttributeOwner": "Class'/Script/Gamekit.GKAttributeSet'"
                },
                "Value": [ 10, 9, 8, 7 ]
        },
        "Cooldown": [ 0.5, 9, 8, 5 ],
        "Price": 0,
        "MaxStack": 1,
        "AreaOfEffect": 50,
        "CastMaxRange": 500,
        "CastMinRange": 0,
        "AbilityBehavior": "PointTarget",
        "AbilityTargetActorClass": "BlueprintGeneratedClass'/Game/Abilities/TargetActors/ControllerTrace.ControllerTrace_C'",
        "TargetObjectTypes": [],
        "CastTime": 0.20000000298023224,
        "ChannelTime": 0,
        "AbilityAnimation": "Attack",
        "ProjectileActorClass": "BlueprintGeneratedClass'/Game/Abilities/Projectiles/BP_GA_Projectile.BP_GA_Projectile_C'",
        "ProjectileSpeed": 1000,
        "ProjectileBehavior": "Directional",
        "ProjectileRange": 1600,
        "AOEActorClass": "None"
}

Ability Kinds

MaxLevel = HeroLevel / 2 UltimateMaxLevel = HeroLevel / 6

• Standard Ability

  • 4 Levels, Every 2 level character increase their maximum basic level ability by 1

• Ultimate Ability

  • 3 Levels, every 6 level

• Abilities with charges

  • Ability consume charges, charges are given by an effect periodically

• Passive abilities

  • Ability simply provide a permanent effect that can be temporarlly disabled with breaks

• Linked Abilities [TODO]

• Sub abilities [TODO]

• Autocast abilities [TODO]

• Modifier abilities [TODO]

Overview

Ability DataTable Initialization

Ability Activation Flow

Ability Replication Flow

Animations

To make abilities generic, the animations montage themselves are not specified. Instead an animation kind is set (Channelling, Attack, Cast, etc..) which is a single enumerator EGK_AbilityAnimation representing the kind of annimation an ability can use.

The animation montage are specified by the Character itself through its FGKAnimationSet (inside FGKUnitStatic) which our ability can sample from.

When an ability is activated the FGKAnimationSet is fectched from the character to the ability and the right animation is then played. This enable us to use the same ability for different characters which can have different animation as well.

Ability Queue

User Interface

Spell Button States

See UGKAbilityWidget for a basic set of implementable event

Here is a list of states you might want to consider when implementing a spell button.

1. Ability is available and can be casted (UMG State Normal)

2. Ability is picking a target

3. Ability is being cast (Animation)

4. Ability is on cooldown

5. Backswing animation

6. Ability requirements/cost are not met

7. Ability cannot be cast because of debuff

Ability under cooldown

Ability disabled

Ability ready

Ability selecting a target

Ability out of mana

Ability disabled by gameplay effect

Ability with activation charges

UI & Ability State

The easiest way to bind the ability is to leverage the UGKAbilityWidget coupled with UGKAbilitySystemEventManager.

1. Instantiate a new UGKAbilitySystemEventManager, call SetupDelegates to start listenning to events from the UAbilitySystemComponent

2. Register UGKAbilityWidget to the event manager using AddAbilityWidget then SetupAbilityWidgetDelegates to start receiving events.

Note

AddAbilityWidget expects an interger as ID, by default it uses FGameplayAbilitySpec.InputID. The behaviour can be overiden by implementing GetWidgetIDFromAbilitySpecHandle and GetWidgetIDFromAbilitySpec.

Currently InputID was used over FGameplayAbilitySpecHandle because it allows us to create Ability widget before the ability is even granted.

Builtin Abilities

• Base Ability: Basic ability with activation logic

• Cancel Ability: Cancel all the current abilities

• Move Ability: Move to destination or Actor

• Base Skill: Ability that is disabled when silenced

• Base Item: Ability that is disabled when muted

  • with an optional item slot (Gloves, ring, etc…)

Builtin Effects

• Cooldown: block the casting of an ability for a given amount of time

• Death: Remove all active effects and set health to zero

• Dispel: Remove all debuffs and disables

• Heal: Heal ocne

• HealOvertime: Heals over time

• Damage: Deals damage once

• DamageOvertime: Deals damage overtime

• Immunity: Grant immunity against all debuffs and disables

• IncreaseHealth: Increase health

• ManaCost: Remove mana from character

• MoveHaste: Increase movement speed

• Root: Prevent the character from moving

• Silence: Prevent the character from casting spells

• Stun: Completely disables the character

Builtin Attribute Set

• Health

• Mana

• Experience

• Gold

Extending Gameplay Ability system

• Add delegates to the component

AI

• You can use TriggerAbilityFromGameplayEvent to trigger abilities without going though target selection

Ability Queue

The ability queue is build by the AbilityQueue Ability, it is its own ability. It is only available on the client

Classes

Relevant classes:

• UGKGameplayAbility: basic Gameplay Ability for skills and items, implements a few top down casting options

• FGKAbilityStatic: configurable settings for abilities

• AGKAbilityTarget_Actor: used to select a target for a given ability

• UGKAbilitySystemComponent

• UGKCastPointAnimNotify: used to notify the ability when the animation reached a given point

• UGKAttributeSet: defines a set of attributes for characters (Health, Mana, Stamina, etc…)

• UGKAbilityWidget: defines a basic interface for widget representing an ability state

Resources

[1]

Gameplay Ability System GAS.