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Make any actor interactable

By the end of this page, any actor of yours shows a prompt when a player looks at it, and does something when they press E. You implement one interface on the actor. The player character is not touched.

If you have not read How interaction works, start there.

  • The interface: Content/MPFriendslop/Blueprints/Interfaces/BPI_Interactable
  • The example to copy from: Blueprints/Environments/Fixtures/BP_InteractButton

The recipe

  1. Open your actor Blueprint and click Class Settings.
  2. Under Implemented Interfaces, click Add and pick BPI_Interactable.
  3. In My Blueprint, under Interfaces, open GetInteractionData. Return the three values:
    • Prompt: the line shown under the ring, for example "Open Crate".
    • Type: Simple, Hold or Spam.
    • Duration: for Hold, the hold time in seconds. For Spam, how full the ring must get (see below). Ignored for Simple.
  4. Open CanInteract and return true when the object may be used right now. Return false when it is locked, already used, or busy.
  5. Add the Interact event. This is where the object does its work. It runs on the server.
  6. In Interact, change a variable set to Replicated or RepNotify, and let that variable drive what the players see. Rules for your own additions says why.
  7. Compile and save, place the actor in the level, and look at it.

StartFocus and EndFocus are optional. They fire on the looking player's machine only, so use them for a cosmetic highlight and nothing else.

A good habit is to expose the prompt, type and duration as variables on the actor, in a Settings|<Sub-category> of your own, and return them from GetInteractionData. That is what BP_InteractButton does with its Prompt, Type and Duration fields, so each placed button can say something different.

The actor settings that break it silently

Setting Where If it is wrong
Replicates Class Defaults, Replication The server cannot find the actor the player used, and nothing happens
Collision on the Visibility channel the mesh's Collision Presets Set to anything but Block, the player's trace goes through: no prompt, no use

Warning

Tick Replicates even when your actor has nothing else to replicate. The player's request names the actor it used, and the server can only read that name for a replicated actor. Without it, the prompt and the ring work on the player's screen and the use is simply lost, with no error.

Hold or mash

You do not add a trigger or a timer for either. The object returns its Type, and the one IA_Interact action handles all three.

Type What the player does What you set
Simple One press nothing else
Hold Holds E until the ring fills. Looking away or stepping out of range cancels it Duration, in seconds
Spam Presses E again and again. Each press fills the ring a little, and it drains between presses Duration, the amount to reach: each press adds Spam Press Gain (0.15 by default), so 1.2 takes eight quick presses

How much each press adds and how fast the ring drains is set on the player, not on the object: Spam Press Gain and Spam Decay Rate on BP_InteractionComponent, in Settings|Interaction. They apply to every Spam object the player uses.

Add the outline

Interactive objects in the template carry a thin dark outline, so players can tell them from scenery. It is a permanent marker, not a highlight that appears when you look at the object. Your actor opts in with one component.

  1. Add a BP_OutlineComponent to your actor.
  2. In Mesh Names, list the names of the mesh components to outline, exactly as they appear in the Components panel. The default is Mesh.
  3. Make sure your level has a post process volume with Infinite Extent (Unbound) ticked and MI_InteractableOutline in its blendables. L_Procedural has one, labelled PostProcess_InteractableOutline, in the outliner folder Lighting. Copy it into your own level.

The look of the line (thickness, colour, opacity, fade with distance) is on MI_InteractableOutline, in Materials/PostProcess/, and applies to every outlined object at once.

Two things to know about the outline:

  • It is written when the game starts. To see it in the editor viewport too, tick Render CustomDepth Pass and set CustomDepth Stencil Value to 1 on the mesh in your Class Defaults.
  • At most 255 actors can be outlined at the same time.

To make your object switch a door or another actor instead of doing the work itself, see Link a button or a lever to a door.

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