Create a multiplayer RPG with Unreal Engine's Gameplay Ability System (GAS)!

section 2 project creation

5 the base character class

• 下载调试集
• rider
  • debug game
    • 
  • 以调试运行
    • 
• VS
  • debuggame editor

2-6 Player and Enemy Characters

• 调整文件位置
• 创建新的继承 AuraCharaterBase 的 c++ 文件
  • AuraCharacter
  • AuraEnemy

2-7. Character Blueprint Setup

• create weapon component in base

• setup weapon attachment

• make weapon no collision

• add the socket under hand_l

  • use staff to preview

• do the same for goblin_spear

2-8 Animation Blueprints

• auro

  • create ABP_Aura
  • state machine
    • main states
      • override initialize animation
      • 
    • slot
    • 
  • set the corresponding abp

• enemy

  • crate animation blueprints template to share between different enemies
  • 
  • 
  • 
  • override initialize animation
    • 
    • 

• abp for goblin spere

  • parent class abp_enemy
  • asset override
    • 
  • assign abp
    • 

• do the same for a new enemy Goblin_Slingshot

2-9 Enhanced Input

• create folder Input, InputActions
  • IA_Move
    • Axis2D Vector 2D
      • AD - x
      • WS - Y
  • IMC_AuroContext
    • ad
      • A - Modifier - negate - X
    • ws
      • modifier
        • S - Modifier - negate - Y
        • swizzle input axis values
          • YXZ
• create AuraPlayerController
  • 

2-10 Aura Player Controller

• 创建 public 同名构造函数 以及 protected 重载函数 BeginPlay

  • 
  • private - inputmapping context (需要提前声明)
    • 

• cpp

  • replicates 为 true
  • 重载 beginplay
  • check inputcontex is valid
  • assign subsystem
  • 设置 mouse 行为和 inputmode

• 需要在 Aura.Build.cs 里面添加对 EnhancedInput module 的引用

• 需要在 h 文件中添加对 EnhancedSubsystem 的引用

#include "EnhancedInputSubsystems.h"

2-11 Movement Input

• override SetInputComponent
  • cast check
• add move action and move function
• bind moveaction
• implement movement logic
• create player controller blueprint

2-12 game mode

• create AuraGameModeBase c++ class based on the game mode base, put under Public/Game folder
• create AuraGameMode with the base class
  • set up player controller calss
  • default pawn class
  • 
• setup gamemode override
• add player start
• add springarm and camera under capsule
  • springarm - distance 750, y -45, camera lag
  • camera - use pawn control rotation = false
• cpp
  • character
    • h
      • 创建构造函数
    • cpp
      • rotate to movement direction
      • constraint to plane
      • limit rotaion
• editor
  • springarm
    • uncheck inheirt pitch yaw roll
  • fix head jerk
    • add another state of idle, make it loop
    • change idlemoverun -> running
    • transition condition -> ShouldMove

2-13 Enemy Interface

• highlight enemey when hover
  

• create cpp class based on unreal interface `EnemyInterface

• create pure virtual function HighlightActor and UnHighlightActor in the h.

• need to override the pure virtual funciton from the auraenemy class

  • override in the h.
  • define in the cpp

2-14 Highlight Enemies

• execute every frame
• override PlayerTick in AuraPlayerController
• create private function CursorTrace
  • save hit result and cast to ienemyinterface
• define pointers with wrapper `TScriptInterace<>
• handle the highlight and unhighlight logic
  • when hovering
  • and make the bool value correct
• visualize the highlight effects
  • draw debug sphere when highlighted
  • make enemy is blocking the trace
    • mesh - collision preset - visibility (block)

2-15 Post Process Highlight

• create enmey base bp, based on aura enemy class
  • make spere and slingshot inheirt
• create post process volume in the level
  • make it infinite
  • add pp material
  • set the project setting - custom depth-stencil pass = Enabled with Stencil
• set render custom depth
  • set render custom depth = true when highlighted
  • set correct stencil value, define this as a const
• reset the collision preset of sphere to default
  • set the collision preset for the enemybase class
    • create constructor in h.
    • make sure the visibility channel is blocked

3

16 The Gameplay Ability System

17 - The Main Parts of GAS

• ability system component - to be added to actor
• attribute set -
• gameplay ability -
• ability task
  • asynchro execute code
• gameplay effect
  • change attributes
• gameplay cues
  • cosmetic effects
• gameplay tag

• add ability system and attribute set to pawn vs. player state
  • pawn
    • live together with the pawn
    • if pawn die, attribute lost
  • player state
    • persist across life
    • make pawn simple

18 - the player state

• new cpp AuraPlayerState
• add constructor
• set netupdate frequency = 100. f
• create blueprint based on the class BP_AuraPlayerState
• set the player state in the game mode

19 - Ability System Component and Attribute Set

• enable the gameplay ability plugin
• create new cpp class AuraAbilitySystemComponent, AuraAttributeSet
• Aura. Build. cs to add module
  • GameplayAbilities
  • GameplayTags
  • GameplayTasks

20 - GAS in Multiplayer

• server

  • game mode
  • all
    • player state
    • pawn

• client

  • own
    • player controller
    • HUD
      • widgets
  • all
    • player state
    • pawn

• net update frequency

  • server -> client update = one-way replication

21 Constructing the ASC and AS

• create pointer inside AuraCharaterBase , and forward declare
  • ASC
  • attributeset
• construct
  • AuraEnemy
    • and make it replicated
• do the same for AuraPlayerState
  • AuraPlayerState

• inherit `IAbilitySystemInterface

  • in AuraCharaterBase
  • remove Gameplayability reference in private range
  • check if an actor have the AbilitySystem and could get it easily
  • need to override
    • `virtual UAbilitySystemComponent* GetAbilitySystemComponent() const = 0;

• create a GetAttributeSet in AuraCharaterBase .h

• do the same for the AuraPlayerState

22 Replication Mode

• setreplication mode for AbilitySystemComponent

• replication mode
  • depends on gameplay effects
  • full
    • to all clients
  • mixed
    • replicated to the owning client
  • minimal
    • not replicated

23 - Init Ability Actor Info

• AbilitySystemComponent and attributeset is implemented for

  • AuraEnemyBase
  • AuraPlayerState

• but AuraCharaterBase do not have a valid construction

• owner of the AbilitySystemComponent and attributeset are different for player character

  • 

• can only init ability actor info after possesion (valid)

  • 
    

24 - Attribute

• attributeset will be bound to AbilitySystemComponent automatically
  • but if there are different attributeset, they need to be different classes
  • we could also use just 1 attributeset

• use gameplay effect to change attribute

• without prediction will bring long delay
  

• with prediction

  • do not need to wait the validation result of server
  • but server can reset the number if it is invalid
    

• max value != base value

  • to be a seperate attributeset

25 - Health and Mana

• add attribute to attributeset

• construct the attributeset

• create health, make it replicated, blueprint read only,

  • create OnRep_Health function, set OldHealth reference as parameter
  • use the GAEMPLAYATTRIBUTE_REPNOTIFY

• to make variable replicated, need to override a GetLifetimeReplicatedProps function

• steps to add a new attribute (boilerplate)

  • declare the variable, make it replicated,
  • make it rep notify (create OnRep... function)
    • implement with GAMEPLAYATTRIBUTE_REPNOTIFY
  • add inside GetLifetimeReplicatedProps with DOREPLIFETIME_CONDITION_NOTIFY

• add live template in Rider to save some time

26 - Attribute Accessors

• usually we do not change attribute from code, but use gameplay effects
• but we could do it from code too
• add define of ATTRIBUTE_ACCESSORS
• check results in game with showdebug abilitysystem

27 - Effect Actor

• is not the best way to change attribute from code, the best way is to change with gameplay effect

• create new cpp class AuraEffectActor

• create sphere and static mesh

  • set mesh as the root component
  • attach sphere to mesh

• following is create callback for delegate

• create a public OnOverlap function

• bind the OnOverlap function to sphere in BeginPlay

  • as callback function

• create a public OnEndOverlap fucntion

• if an actor has derived IAbilitySystemInterface, then it should have AbilitySystemComponent

• when overlap, + 25 HP

28 - Game UI Architecture

• UI
  • View (display)
  • Widget Controller (data process)
  • Model (data)

• these are decoupled

29 - Aura User Widget and Widget Controller

• create new cpp class

  • AuraUserWidget (UserWidget)
  • AuraWidgetController (Object)

• in AuraUserWidget

  • public
    • create controller variable
    • UFUNCTION(BlueprintCallable) SetWidgetController (UObject* InWidgetController)
  • protected
    • create WidgetControllerSet () UFUNCTION(BlueprintImplementableEvent)
      • will be called after WidgetController is set

• AuraWidgetController

  • protected
    • UPROPERTY (BlueprintReadOnly, Category = "WidgetController") TObjectPtr<APlayerController> PlayerController
    • UPROPERTY (BlueprintReadOnly, Category = "WidgetController") TObjectPtr<APlayerState> PlayerState
    • UPROPERTY (BlueprintReadOnly, Category = "WidgetController") TObjectPtr<UAbilitySystemComponent> AbilitySystemComponent
    • UPROPERTY (BlueprintReadOnly, Category = "WidgetController") TObjectPtr<UAttributeSet> AttributeSet

30 - Globe Progress Bar

• create new bp
  • WBP_GlobeProgressBar (AuraUserWidget )
    • SizeBox_Root (make it variable)
      - desired

      • Overlay_Root

        • Image_Background (is variable)
          - fill vertically, horizontally
        • ProgressBar_Globe (is variable)
          - fill vertically, horizontally
          - backgroud image
          - tint - transparent
          - style - fill image
          - MI_HealthGlobe
          - draw as image
          - Fill Color and Opacity = white
          - bar fill type - bottom to top
        • Image_Glass (is variable)
          - fill vertically, horizontally
          - alpha = 0.5

      • create function UpdateBoxSize to override box width and box height

        • create float variable (Category - GlobeProperties)
          • BoxWidth
          • BoxHeight

      • create function UpdateBackgroundBrush to set BackgroundBrush

        • create variable BackgroundBrush (Slate Brush)

      • create function UpdateGlobeImage

        • create variable ProgressBarFillImage

      • create function UpdateGlobePadding

        • create variable GlobePadding

      • create function UpdateGlassBrush

        • create variable GlassBrush

      • create function UpdateGlassPadding

31 - Health Globe

• create WBP_HealthGlobe

  • show inherited variables
  • update progressbarfillimage

• create WBP_Overlay

  • Canvas Panel
    • WBP Health Globe
      • anchor bottom center

• preview with level blueprint

• do the same for WBP_ManaGlobe

32 - Aura HUD

• remove those testing bp from level blueprint
• create AuraHUD cpp
  • UAuraUserWidget - OverlayWidget
  • UAuraUserWidget - OverlayWidgetClass
  • override beginplay
    • create widget and add to viewport

33 - Overlay Widget Controller

• create struct FWidgetControllerParams

• create public function SetWidgetControllerParams

• CREATE OverlayWidgetController based on AuraWidgetController

• create GetOverlayWidgetController function inside AuraHUD .h

• create InitOverlay function inside AuraHUD .h