Game Code Mastery

Input Buffer System Usage Guide

6 min read

This guide provides detailed instructions on using the Input Buffering System in an Unreal Engine 5 project, covering key workflows for queuing inputs, managing buffer states, and extending the system with custom input actions. Users will learn how to trigger buffered inputs, integrate with abilities, and create custom input behaviors for Souls-like Action RPGs. The guide is designed for developers and designers to effectively utilize input queuing for responsive combat mechanics.

Queuing Inputs

Queue inputs during action commitments to ensure they execute when the buffer window closes.

  1. Ensure the BP_InputBufferComponent is added to the pawn (e.g., BP_PlayerCharacter).

  2. On input action events, call Store Input In Buffer with the appropriate InputTag and Input Status:

    Enhanced Input Action (IA_Dodge, Triggered) -> Get Component By Class (Class: BP_InputBufferComponent) -> Store Input In Buffer (InputTag: InputTag.Dodge, bConsumeInputBuffer: true, Input Status: Pressed)
    Enhanced Input Action (IA_Dodge, Completed) -> Get Component By Class (Class: BP_InputBufferComponent) -> Store Input In Buffer (InputTag: InputTag.Dodge, bConsumeInputBuffer: false, Input Status: Released)

  3. Verify the input is queued during an ANS_InputBuffer window (e.g., in AM_Heal).

Managing Buffer Windows

Control when the input buffer opens and closes using ANS_InputBuffer in Animation Montages.

  1. Open an Animation Montage (e.g., SwordSwing_Montage).
  2. Add an ANS_InputBuffer Anim Notify State to the frames where input buffering is needed.
gantt
    title Sword Swing Animation (30 Frames, 30 FPS)
    dateFormat YYYY-MM-DD HH:mm:ss.SSS
    axisFormat %Lms
    tickInterval 200ms
    section Animation
    Full Animation Duration (Frames 1-30) :s1, 2025-05-14 21:00:00.000, 2025-05-14 21:00:01.000
    section Notify
    Input Buffer Active (Frames 10-15) :crit, active, 2025-05-14 21:00:00.333, 2025-05-14 21:00:00.500

IMPORTANT NOTE:

If you ever have the issue of the notify state being called twice, E.g. Buffered Input Actions cancel into each other when spamming inputs, make sure to change the Montage Tick Type to Branching Point.

Managing Buffer States

  1. The buffer opens on notify start, queues inputs, and consumes the last input on notify end, triggering On Input Buffer Consumed.

  2. Bind to buffer state events for additional logic:

    BP_InputBufferComponent -> On Input Buffer Opened -> Spawn Emitter At Location (Emitter: BufferStartFX)
    BP_InputBufferComponent -> On Input Buffer Closed -> Log Message (Text: Buffer Closed)

Handling Consumed Inputs

Process buffered inputs when the buffer consumes them, executing actions or abilities.

  1. In BP_PlayerCharacter, bind to the On Input Buffer Consumed event on BP_InputBufferComponent.

  2. Use a Switch on Gameplay Tag to handle different InputTag cases:

    On Input Buffer Consumed (InputTag) -> Is Character Dead? -> Branch (False) -> Switch on Gameplay Tag (InputTag) ->
  Case InputTag.Dodge -> PerformDodge
  Case InputTag.Attack -> PerformAttack

  3. Ensure the pawn validates state (e.g., not dead) before executing actions.

Integrating with Abilities

Bind abilities to buffered inputs using the Advanced Abilities System or custom logic.

  1. Using Ability Set or Combat Style:

    • In the Ability Set or Combat Style Data Asset, assign abilities to InputTag values (e.g., InputTag.Dodge to GA_Dodge).
    • Grant the Ability Set to the pawn on Event BeginPlay: 
      Event BeginPlay -> Get AbilitySystemComponent -> GiveAbilitySets(AbilitySet: AS_Combat)
    • Buffered inputs automatically trigger associated abilities when consumed.

  2. Manual Binding:

    • In On Input Buffer Consumed, activate abilities manually: 
      OnInputBufferConsumed (InputTag: InputTag.Dodge) -> ActivateAbilityByClass(Class: GA_Dodge)

Creating Custom Input Actions

Extend the system by adding new input actions with custom behaviors.

  1. Create a new Gameplay Tag in the Gameplay Tag Manager (e.g., InputTag.MyNewInput).

  2. In Project Settings > Input, create a new Input Action (e.g., IA_MyNewInput) and map it to a key in the IMC_Combat Input Mapping Context.

  3. In BP_PlayerCharacter, bind the input action’s Pressed and Released events:

    Enhanced Input Action (IA_MyNewInput, Triggered) -> Get Component By Class (Class: BP_InputBufferComponent) -> Store Input In Buffer (InputTag: InputTag.MyNewInput, bConsumeInputBuffer: true, Input Status: Pressed)
    Enhanced Input Action (IA_MyNewInput, Completed) -> Get Component By Class (Class: BP_InputBufferComponent) -> Store Input In Buffer (InputTag: InputTag.MyNewInput, bConsumeInputBuffer: false, Input Status: Released)

Note:

bConsumeInputBuffer determines which StoreInputInBuffer call consumes the input and activates the input action. So set this value to true on the input where you wish for the input to actually happen and set it to false on the other input event.

  1. Add ANS_InputBuffer to relevant Animation Montages (e.g., MyAction_Montage) for buffering.

  2. If no montage exists, create Animation Montage for animation associated with the input.

  3. In On Input Buffer Consumed, add a new case for InputTag.MyNewInput:

    On Input Buffer Consumed -> Switch on Gameplay Tag -> Case InputTag.MyNewInput -> PerformMyNewAction

  4. Test the new input in-game to ensure it buffers and triggers correctly.

Example: Dodge Action

  1. Setup InputTag.Dodge, IA_Dodge, and add the new input action to desired Input Mapping Context.

  2. Create Dodge Input events in Pawn or Character and on Pressed and Released events call StoreInputInBuffer from the Pawn or Characters InputBufferComponent.

    • Call StoreInputInBuffer(InputTag.Dodge, true, Press)
OnMyInputPressed:
  -> StoreInputInBuffer(InputTag.MyNewAction, true, Press)
OnMyInputReleased:
  -> StoreInputInBuffer(InputTag.MyNewAction, false, Release)

  1. Create Dodge Action or Ability

    1. The dodge ability or action is the part that ultimately plays the dodge animation.

  2. In the On Input Buffer Consumed, trigger the dodge logic.

OnInputBufferConsumed:
// If Using with Abilities System
  -> if(IsAlive()) -> GetAbilitySystemComponent -> TryActivateAbilitiesByTag(->BufferedInputTag) // will use the dodge tag to automatically activate the ability by tag 
  
  // If Using Standalone without Ability System
  -> if(IsAlive() && BufferedInputTag == InputTag.Dodge) -> PerformDodge() // Function for actually performing dodge action and playing dodge animation

NOTE:

If integrating with Abilities System be sure to create the corresponding ability and grant the ability using an ability set associated with the input tag. Check Ability System Documentation for more information.

  1. Create Dodge Animation

    1. Create as Animation Montage.
    2. Associate animation with Dodge Action or Ability.

  2. Add Input Buffer notify state in dodge animation

    1. Adjust to desired position and duration.

  3. If Using Abilities System:

    1. Grant Dodge Ability Using a Combat Style or Ability Set, setting the associated tag to InputTag.Dodge.
    2. Correctly grant abilities and associate the ability with the input tag
      1. To grant input-bound abilities, use GiveAbilitySets on the actor’s AbilitySystemComponent, or associate the ability with the appropriate weapon CombatStyle.

Troubleshooting

  • Inputs Not Triggering:
    • Confirm On Input Buffer Consumed is bound and handles the correct InputTag.
    • Ensure ANS_InputBuffer is on the Animation Montage and the montage plays correctly.
    • Verify bConsumeInputBuffer is true for the intended trigger event (Pressed or Released).
  • Buffer Not Opening:
    • Check that ANS_InputBuffer is correctly placed in the Animation Montage and the Animation Blueprint references it.
    • Ensure BP_InputBufferComponent is not disabled on the pawn.
  • Unexpected Input Behavior:
    • Verify unique InputTag values to avoid conflicts.
    • Check that bConsumeInputBuffer is false for non-trigger events to prevent premature consumption.
  • Abilities Not Activating:
    • For Advanced Abilities System, ensure abilities are granted via Ability Set or Combat Style with matching InputTag values.
    • Confirm the pawn has the Gameplay Ability System component and abilities are not blocked.

Best Practices

  • Workflows:
    • Use hierarchical InputTag naming (e.g., InputTag.Combat.Dodge) for organization.
    • Test new inputs with existing Animation Montages before creating custom ones.
    • Centralize input handling in On Input Buffer Consumed for maintainability.
  • Pitfalls to Avoid:
    • Don’t add ANS_InputBuffer to every Animation Montage; reserve it for committed actions.
    • Avoid binding On Input Buffer Consumed multiple times, as it may cause duplicate executions.
    • Don’t set bConsumeInputBuffer to true for both Pressed and Released unless intentional.
  • Performance Considerations:
    • Use specific InputTag filters in Store Input In Buffer to avoid queuing irrelevant inputs.
    • Optimize On Input Buffer Consumed logic to avoid complex branching for large input sets.

Graph View