Interactive Items

Fair Warning: This is a C++ plugin for UE4

Quick demo video: https://youtu.be/hkKlg-VNaKM

Example project: https://github.com/dakitten2358/InteractionExamples

How To

Setup Interactive Items

Under Class Settings / Implemented Interfaces add the interface Interaction Interface. Under Interfaces, provide implementations for:

• IsInteractionTarget Can this item be currently interacted with?
• GetInteractionType Is this an instant interaction, or one that requires time?
• GetInteractionDetails Text + image for the interaction
• GetInteractionWorldLocation By default, objects will use their Actor location, but can be overridden using this

To respond to the interaction, add the event Interact from the Interaction Interface to your blueprint graph. This will be called with Authority, so pay attention if you need to modify something on the clients (e.g. hiding the mesh, etc) that isn't auto replicated.

Highlighting of the item can be controlled via the events StartInteractionHighlight and StopInteractionHighlight. These will only be called on the local client.

Setup UI

Create a Widget that will represent your interaction widget (InteractionWidget is the default, and can be used). Ensure that it implements the Interaction Widget Interface.

Create a Widget that will represent your main HUD UI, and add your interaction widget to it. Ensure that the UI implements the Interaction Widget Interface as well.

Your HUD object should create the UI widget, and add it to the viewport. Add an InteractionSensingComponent to your HUD object. OnInteractionTargetUpdated will get called when there is a change in the interaction target. You can check the source via Stimulus Interaction Type, which will be one of Show (a new object is being shown), Update (need to reposition the UI, update progress, etc), and Hide. These should be forwarded to the UI via the Interaction Widget Interface calls ShowInteractionWidget, UpdateInteractionWidget and HideInteractionWidget.

Interaction

Assign an action mapping for interaction. Under the settings for the plugin make sure the action name matches. Add an InteractionInvokerComponent to your pawn/character, and connect the InputAction's Pressed and Released to BeginInteraction and CancelInteraction.

Additional

Tracing methods

There's three tracing methods you can use:

• CameraAndPawn This is the default, and will trace from the camera to the center of the screen to find a target, and then will trace again from the actor's location to the target found by the initial trace. This helps w/ windows, etc. where the player can see the interactive item, but may not be able to reach it. This is ideal for third person over the shoulder/offset cameras.
• Camera This simply checks from the camera to the center of the screen. This is fine for first person modes.
• Pawn Checks from the actor location in the direction the actor is facing. Best for top down (or nearly) views.

Debugging

ShowTraces will turn on a per frame trace.

This seems like a lot of work!

It is! I'll be adding some helper classes to provide basic implementations of really common things, but I want to avoid bloating the plugin with classes and content that should be replaced by the game itself.

How did you do the progress circle?

https://www.tomlooman.com/circular-progress-bar-for-umg/

Highlighting

I didn't include the material used for highlighting as it's not mine; I'm currently using Local Outlines (https://www.unrealengine.com/marketplace/en-US/slug/local-outlines). I intend to replace this with my own method and include it in the plugin.