🛠️NPC Dialogue Game

This example project demonstrates making a simple non-linear dialogue-based game when beginning with some pre-existing assets.

Goals

Display Yarn dialogue in a Unity scene
Allow a player to select between options to respond
Allow a player to select among available characters to speak to
Use Yarn Spinner to trigger a command that changes the interactability of characters

Materials

Yarn Spinner installed in Unity
Yarn Spinner set up in a text editor
Starter Asset Package downloaded and unzipped

Instructions

Open a new Unity 3D project. Ensure Yarn Spinner has been added to the project in the Package Manager as per the Installation Instructions.

Drag the provided Asset Package into the Project Window where project files are displayed in Unity to import them into the project.

This package includes the following assets and functionality:

A simple, static environment called Graveyard which also contains four character models.
A C# script that provides simple functions for the character objects.
A Timeline that stores the hovering animation for the Ghost character.
Some Lights that turn on and off to indicate when a Grave character is speaking.

Creating a Runnable Script

The next step is to import the Dialogue System and hook up a Yarn Project and Yarn Script. If you have completed Example Project 1 or Example Project 2 before, you may skip ahead to Filling Out Your Script. Otherwise, let's proceed!

Yarn Spinner for Unity comes with a pre-made UI layer and accompanying utility scripts to handle displaying lines and presenting options from Yarn files. In the Project Window again, navigate to Packages > Yarn Spinner > Prefabs and drag Dialogue System.prefab into the scene.

When the Dialogue System in the scene is selected, the Inspector will display the Yarn Project it is expecting line from. Here, a Yarn Project is a kind of linking file that groups Yarn script files together. To make one, navigate to a sensible place for the file to live (such as Assets > Dialogue) and right-click the Project Window pane to select Create > Yarn Spinner > Yarn Project.

The existence of Yarn Projects allows larger games with multiple dialogue systems (e.g. main story dialogue, barks, storylets) to separate into multiple projects that pass lines to different UI or systems. This allows an extra level of organisation above separate Yarn files which are typically used to separate story scenes or parts.

However, most games will need only a single Yarn Project.

Select the scene's Dialogue System again and drag the new Yarn Project into the labelled slot in the Inspector.

Now the Yarn Project needs one or more Yarn Scripts to get dialogue from. Just like with the Yarn Project, navigate to the desired file location and select Create > Yarn Spinner > Yarn Script. Then, with the Yarn Project selected, drag the newly created script into the Inspector slot labelled Source Scripts. Click Apply.

Filling Out Your Script

By default, a new Yarn Script begins with a single empty node with the name of the file. Open the file, rename the node to Start and put a single line of test dialogue. You may remove the tags field.

title: Start
---
This is a line of test dialogue.
===

Returning to Unity, pressing the ▶️ button results in the test line being displayed in front of the graveyard scene. Pressing Continue will make the UI disappear, as it has reached the end of the script.

It's time to plan a story. In the scene there are four characters—Ghost, LeftGrave (Louise), CenterGrave (Carol), and RightGrave (Ruby)—and the intent of this game is for the player to be able to interact with them in virtually any order to complete the objectives of the game. This game format typically accompanies stories where the player must piece together information from smaller tidbits given to them when they speak to different characters.

For example: neither Witness A nor B knew who stole the cookie from the kitchen, however:

Witness A knew the cookie was taken in the morning.
Witness B knew that Suspects A and B entered the kitchen in the morning and afternoon, respectively.

Together, their clues show that Suspect A must have eaten the cookie.

So, when the game begins, Ghost will present some mystery. Once a brief context-establishing conversation ends, the player will be free to select which character to speak to next. Speaking to each of the Grave characters will present a clue, provided the required prerequisite clues are known. At any time, the player can present their collated clues to Ghost. If their clues are complete, Ghost will tell them they solved the mystery and the game will end.

This short story provides a looping circuit through four paths, and results in the player reaching the ending after an undetermined number of conversations (though there is a hypothetical minimum, there is no maximum). A railroad diagram representation of the story would look as follows:

So it's time for the actual writing part. Here, I've opened my new Yarn Script in Visual Studio Code with the Yarn Spinner Extension installed as per the Installation Instructions. I've written a minimal script that follows the planned story, as a skeleton that can be expanded on later.

In this script, selecting the correct conversation option when speaking to each character will yield a new clue. However, the correct option is only available if the player has the required prerequisite clues. So no matter the order the player speaks to the graves, they must acquire clues in the order A then B then C.

The most notable part about this script is that there are no jump statements in the file at all; each node is completely disconnected from the rest. Instead, we will be requesting and jumping to specific nodes manually from within Unity.

You can find this example script below to copy. Or if you want to make you own version and need a refresher on how to represent it in Yarn, refer to the Syntax and File Structure guide.

GhostyLads.yarn

title: Start
---
<<set $hasClueA to false>>
<<set $hasClueB to false>>
<<set $hasClueC to false>>
Ghost: Welcome to the graveyard! Unfortunately, you're just in time for an unsolved mystery...
Ghost: You'll have to speak to these three to figure out what happened!
===
title: LeftGraveLouise
---
Louise: What do you want to know?
-> Something that will get me no clues?
-> Something that will get me Clue A? <<if not $hasClueA>>
    <<set $hasClueA to true>>
-> Something relating to existing Clue A? <<if $hasClueA>>
-> Something relating to existing Clue B? <<if $hasClueB>>
-> Something relating to existing Clue C? <<if $hasClueC>>
Louise: ~additional dialogue~
Louise: Ok, bye!
===
title: CenterGraveCarol
---
Carol: What do you want to know?
-> Something that will get me no clues?
-> Something that will get me Clue B? <<if $hasClueA and not $hasClueB>>
    <<set $hasClueB to true>>
-> Something relating to existing Clue A? <<if $hasClueA>>
-> Something relating to existing Clue B? <<if $hasClueB>>
-> Something relating to existing Clue C? <<if $hasClueC>>
Carol: ~additional dialogue~
Carol: Ok, bye!
===
title: RightGraveRuby
---
Ruby: What do you want to know?
-> Something that will get me no clues?
-> Something that will get me Clue C? <<if $hasClueB and not $hasClueC>>
    <<set $hasClueC to true>>
-> Something relating to existing Clue A? <<if $hasClueA>>
-> Something relating to existing Clue B? <<if $hasClueB>>
-> Something relating to existing Clue C? <<if $hasClueC>>
Ruby: ~additional dialogue~
Ruby: Ok, bye!
===
title: Ghost
---
Ghost: Are you ready to tell me what happened?
-> Yes
    Ghost: Well, what do you know?
    -> I have no clues.
    -> I have clue A. <<if $hasClueA>>
    -> I have clues A and B. <<if $hasClueB>>
    -> I have clues A, B and C. <<if $hasClueC>>
        <<jump Ending>>
    Ghost: That doesn't sound right...
-> No
Ghost: Go on and speak to those three!
===
title: Ending
---
Ghost: You solved it!
===

Once you've got a basic story, pop back into Unity and check the basics:

Lines display correctly
Pressing Continue advances lines correctly
Selecting different options have the expected outcomes

Note that at this point, there is no way to progress beyond the intro conversation with Ghost. All other nodes cannot be reached with the code we have written so far.

Making Players Interactable

In this game, the player should be able to select an NPC in the scene and have it trigger their repsective conversation. This requires a few things:

Code to begin dialogue from a specific node when a character object is interacted with.
Code to disable scene interaction when any character is already speaking.
Code to disable character interaction when a specific character should not be interactable.

In Assets > Scripts there is a C# script that has code to do these things (see headers below), so we just need to connect it to the appropriate places. But first, let's step through what it does.

// this file is attached to every character in the scene and so will affect only
// the targeted character object when functions are called

// disable scene interaction, activate speaker indicator, and
// run dialogue from {conversationStartNode}
private void StartConversation();

// reverse StartConversation's changes: 
// re-enable scene interaction, deactivate indicator, etc.
private void EndConversation();

// make character not able to be clicked on
public void DisableConversation();

Add the YarnInteractable script to each character in the game: Ghost, LeftGrave, CenterGrave, and RightGrave. Make sure to set their respective conversationStartNode values in the Inspector to match what they are called in the Yarn script.

First up is the code for beginning a conversation. This requires running dialogue from a specific node when a character is interacted with. Running dialogue is a simple matter of telling the DialogueRunner to begin dialogue and passing the name of the node to begin from as a string.

// first we need a handle on the DialogueRunner, so we may as well get it when
// this object is first added to the scene
private DialogueRunner dialogueRunner;

public void Start() {
    dialogueRunner = FindObjectOfType<Yarn.Unity.DialogueRunner>();
}

// then we need a function to tell Yarn Spinner to start from {specifiedNodeName}
public string conversationStartNode;

private void StartConversation() {
    dialogueRunner.StartDialogue(conversationStartNode);
}

To run this when a character is interacted with, simple override the OnMouseDown() function that exists for every GameObject (which this class inherits from). Checking the IsDialogueRunning property of the DialogueRunner is a simple way to ignore interaction whenever starting dialogue would interrupt an existing conversation.

private bool interactable; // whether this character should be enabled right now
// (begins true, but may not always be true)

public void OnMouseDown() {
    // if this character is enabled and no conversation is already running
    if (interactable && !dialogueRunner.IsDialogueRunning) {
        // then run this character's conversation
        StartConversation();
    }
}

This handles beginning a conversation, but what if other changes are needed while a character is speaking? Well, having a function that is triggered when a conversation ends would allow properties to be set in StartConversation that can then be reversed once dialogue has ended.

In a typical game, several changes would be triggered when beginning or ending dialogue, such as changing UI mode and starting and stopping a speaking animation on the relevant character or similar. So it's sensible to have bookend functions that hold all this code, even if we won't be doing anything useful with EndConversation()until later.

To trigger a function when a conversation ends, a listener can be added to the DialogueRunner that will fire a specified function when a certain event occurs. The onDialogueComplete event happens whenever the runner reaches the end of its current conversation path.

// this would go in the Start() function, right after finding the DialogueRunner
// object, so that the listener begins before dialogue does the first time
dialogueRunner.onDialogueComplete.AddListener(EndConversation);

Next, let's define the function it will call. A key consideration here is that every object using this YarnInteractable script will be notified of dialogue completion every time it happens. Each one is registering a listener, and each will have its own EndConversation() function be called.

So to save some work, we can check whether this is the instance that should care about the event. This can be done just by setting a boolean when the conversation begins, that says this is the character that is currently speaking.

private bool isCurrentConversation;

private void StartConversation() {
    isCurrentConversation = true;
    // TODO *begin animation or turn on speaker indicator or whatever* HERE
    dialogueRunner.StartDialogue(conversationStartNode);
}

private void EndConversation() {
    if (isCurrentConversation) { 
        // TODO *stop animation or turn off indicator or whatever* HERE
        isCurrentConversation = false;
    }
}

Returning to Unity, press the ▶️ button and see that this now allows a new conversation to be triggered by interacting with any character after another has finished speaking.

At this point, this may seem done, but there is a critical issue here. Looking back at the earlier goals:

Clicking on a character begins dialogue from their respective node.
Clicking on a character while dialogue is already running does nothing.
Clicking on a character when they should not be interactable does nothing.

Why that third thing? Well, because the current state of the game allows the player to:

Speak to the Ghost to begin the story.
Ask the Graves about the mystery.
Speak to the Ghost once they have collected the necessary clues.
Have Ghost tell them they ✨ solved the mystery ✨ and say goodbye.
Go back and still ask the Graves about the mystery that is already solved(?!)

So there needs to be a way to tell a specific character "no, you are done, don't speak to the player any more". This can be done with a simple Yarn Command.

In YarnInteractable.cs there is a simple function that sets a flag that the OnMouseDown() function checks when deciding whether to start a conversation. Turning this into a command simple requires adding the Yarn Command decorator above the function, with the string that will become the command keyword in any yarn scripts.

[YarnCommand("disable")]
public void DisableConversation() {
    interactable = false;
}

Back in the Yarn script, call disable once for each character when the story ends, to save the player from going back and having a confusion conversation about an already-solved mystery.

title: Ending
---
Ghost: You solved it!
<<disable Ghost>>
<<disable LeftGrave>>
<<disable CenterGrave>>
<<disable RightGrave>>
===

And that's it for the dialogue behaviours! Back in Unity, characters should speak when interacted with—but not when it would interrupt another, or when the story has ended.

Draw the Rest of the Owl

Now that all the behaviours are working and the skeleton story plays through correctly, it's time to replace the skeleton placeholder script with the full story and add some polish. In Assets > Dialogue find the file GhostyLads_FinalVersion.yarn. In the Yarn Project created earlier, replace the script you placed in Source Scripts earlier with this script instead.

Next, let's add an indicator so the player more easily knows which character is currently speaking.

Because I am not an animator, I have used only static objects as characters in this demo game. To indicate who is speaking, I will be using a simple spotlight that turns on and off above the speaker. I will not be taking questions at this time.—Mars, 2022.

In the scene, each grave object also contains a green spotlight which is currently assigned to a variable called lightIndicatorObject in YarnInteractable.cs, so a snippet of code in each of theStartConversation() and EndConversation() functions can quickly turn it on and off for the relevant character.

private void StartConversation() {
    isCurrentConversation = true;
    if (lightIndicatorObject != null) {
        lightIndicatorObject.intensity = defaultIndicatorIntensity;
    }
    dialogueRunner.StartDialogue(conversationStartNode);
}

private void EndConversation() {
    if (isCurrentConversation) {
        if (lightIndicatorObject != null) {
            lightIndicatorObject.intensity = 0;
        }
        isCurrentConversation = false;
    }
}

Now, a light should turn on above any grave who is currently speaking.

Result

A playable whodunnit-like game with multiple characters that can be spoken to in any order to solve a mystery from partial clues available.

An easy way to spice this up is to just try replacing provided assets with ones of your own choosing. There are plenty of publically available asset packs with permissive licenses to play with, and re-theming a starter game and building from there can be easier than starting from scratch.

You could add more characters, or even design a more complex conversation structure that must be navigated to solve the mystery! Yarn Spinner is great at telling complex non-linear stories where player choices matter.

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Last updated 2 years ago