NPC-library

A collection of tools for creating Non-Player-Characters (NPCs). These are capable of having conversations with the player, and play different animations.

Capabilities of the NPCs in this library:

• Start a conversation when clicked or when walking near
• Trigger any action when clicked or when walking near
• Trigger any action when the player walks away
• Turn around slowly to always face the player
• Play an animation in the NPC 3d model, optionally returning to loop the idle animation afterwards

The dialog messages can also require that the player chooses options, and any action can be triggered when the player picks an option or advances past a message.

To use NPCs in your scene:

1. Install the library as an npm bundle. Run this command in your scene's project folder:

npm i @dcl/npc-scene-utils -B

2. Run dcl start or dcl build so the dependencies are correctly installed.

3. Import the library into the scene's script. Add this line at the start of your game.ts file, or any other TypeScript files that require it:

import { NPC } from '@dcl/npc-scene-utils'

4. In your TypeScript file, create an NPC type object, passing it at least a position, a path to a 3d model, and a function to trigger when the NPC is activated:

export let myNPC = new NPC({ position: new Vector3(10, 0.1, 10) }, 'models/CatLover.glb', () => {
  myNPC.talk(ILoveCats, 0)
})

5. Write a dialog script for your character, preferably on a separate file, making it of type Dialog[].

import { Dialog } from '@dcl/npc-scene-utils'

export let ILoveCats: Dialog[] = [
  {
    text: `I really lo-ove cats`,
    isEndOfDialog: true
  }
]

NPC Default Behavior

NPCs at the very least must have:

• position: (TranformConstructorArgs). Can include position, rotation and scale.
• model: (string) The path to a 3D model
• onActivate(): (()=> void) A function to call when the NPC is activated.

export let myNPC = new NPC({ position: new Vector3(10, 0.1, 10) }, 'models/CatLover.glb', () => {
  log('NPC activated!')
})

With this default configuration, the NPC behaves in the following way:

• The onActivate() function is called when pressing E on the NPC, and when the player walks near at a distance of 6 meters.
• Once activated, there's a cooldown period of 5 seconds, that prevents the NPC to be activated again.
• After walking away from the NPC, if its dialog window was open it will be closed, and if the NPC was rotating to follow the player it will stop.
• If the NPC already has an open dialog window, clicking on the NPC won't do anything, to prevent accidentally clicking on it while flipping through the conversation.
• If the NPC has an animation named 'Idle', it will play it in a loop. If other non-looping animations are played, it will return to looping the 'Idle' animation after the indicated duration.

Many of these behaviors can be overriden or tweaked with the exposed properties.

NPC Additional Properties

To configure other properties of an NPC, add a fourth argument as an NPCData object. This object can have the following optional properties:

• idleAnim: (string) Name of the idle animation in the model. This animation is always looped. After playing a non-looping animation it returns to looping this one.
• faceUser: (boolean) Set if the NPC rotates to face the user while active.
• turnSpeed: (number) If faceUser is true, turnSpeed determines the speed at which the NPC turns to face the player. 2 by default.
• portrait: (string or ImageData) 2D image to show on the left-hand side of the dialog window. The structure of an ImageData object is described in detail below.
• darkUI: (boolean) If true, the dialog UI uses the dark theme.
• dialogSound: (string) Path to sound file to play once for every entry shown on the UI. If the dialog entry being shown has an audio field, the NPC will play the file referenced by the audio field instead.
• coolDownDuration: (number) Change the cooldown period for activating the NPC again. The number is in seconds.
• hoverText: (string) Set the UI hover feedback when pointing the cursor at the NPC. TALK by default.
• onlyClickTrigger: (boolean) If true, the NPC can't be activated by walking near. Just by clicking on it or calling its activate() function.
• onlyETrigger: (boolean) If true, the NPC can't be activated by walking near. Just by pressing the E key on it or calling its activate() function.
• onlyExternalTrigger: (boolean) If true, the NPC can't be activated by clicking, pressing E, or walking near. Just by calling its activate() function.
• reactDistance: (number) Radius in meters for the player to activate the NPC or trigger the onWalkAway() function when leaving the radius.
• continueOnWalkAway: (boolean) If true,when the player walks out of the reactDistance radius, the dialog window stays open and the NPC keeps turning to face the player (if applicable). It doesn't affect the triggering of the onWalkAway() function.
• onWalkAway: (()=> void) Function to call every time the player walks out of the reactDistance radius.
• walkingAnim: (string) Name of the walking animation on the model. This animation is looped when calling the followPath() function.
• walkingSpeed: (number) Speed of the NPC when walking. By default 2.
• path: (Vector3) Default path to walk. If a value is provided for this field on NPC initialization, the NPC will walk over this path in loop from the start.
• bubbleHeight: (number) The height at which to display the speech bubble above the head of the NPC.
• textBubble: (boolean) If true, NPC starts with a speech bubble object ready to be accessed from the start. Otherwise, they text bubble is only built on the first call to talkBubble() on the NPC.
• noUI: (boolean) If true, no UI object is built for UI dialogs for this NPC. This may help optimize the scene if this feature is not used.

The ImageData type that can be used on the portrait field is an object that may include the following:

• path: Path to the image file.
• xOffset: Offset on X, relative to the normal position of the image.
• yOffset: Offset on Y, relative to the normal position of the image.
• width: The width to show the image onscreen.
• height: The height to show the image onscreen.
• section: Use only a section of the image file, useful when arranging multiple icons into an image atlas. This field takes an ImageSection object, specifying sourceWidth and sourceHeight, and optionally also sourceLeft and sourceTop.

export let myNPC = new NPC(
  { position: new Vector3(10, 0.1, 10) },
  'models/CatLover.glb',
  () => {
    log('NPC activated!')
  },
  {
    idleAnim: `Weight_Shift`,
    faceUser: true,
    portrait: { path: 'images/catguy.png', height: 128, width: 128 },
    darkUI: true,
    coolDownDuration: 3,
    hoverText: 'CHAT',
    onlyClickTrigger: false,
    onlyExternalTrigger: false,
    reactDistance: 4,
    continueOnWalkAway: true,
    onWalkAway: () => {
      log('walked away')
    }
  }
)

Check NPC State

There are several properties you can check on an NPC to know what its current state is:

• .state: An enum value of type NPCState. Supported values are NPCState.STANDING (default), NPCState.TALKING, and NPCState.FOLLOWPATH. TALKING is applied when the dialog window is opened, and set back to STANDING when the window is closed. FOLLOWPATH is applied when the NPC starts walking, and set back to STANDING when the NPC finishes its path or is stopped.
• .introduced: Boolean, false by default. Set to true if the NPC has spoken to the player at least once in this session.
• .dialog.isDialogOpen(): Returns a Boolean, false by default. True if the dialog window for this NPC is currently open.
• .inCooldown: Boolean, false by default. True if the NPC was recently activated and it's now in cooldown. The NPC won't respond to being activated till inCooldown is false.

TIP: If you want to force an activation of the NPC in spite of the inCooldown value, you can force this value to true before activating.

NPC Callable Actions

An NPC object has several callable functions that come with the class:

Talk

To start a conversation with the NPC using the dialog UI, call the talk() function. The function takes the following required parameter:

• script: (Dialog[]) This array contains the information to manage the conversation, including events that may be triggered, options to choose, etc.

It can also take the following optional parameters:

• startIndex: (number | string) The Dialog object from the script array to open first. By default this is 0, the first element of the array. Pass a number to open the entry on a given array position, or pass a string to open the entry with a name property matching that string.
• duration: (number) Number of seconds to wait before closing the dialog window. If no value is set, the window is kept open till the player reaches the end of the conversation or something else closes it.

myNPC.talk(myScript, 0)

Learn how to build a script object for NPCs in a section below.

Speech Bubbles

Besides the UI dialog window, NPCs can show speech bubbles over their heads. This alternative is less invasive to the player, but also non-interactive. Players can't alter the pace of the conversation or provide answers to questions.

For an NPC to talk with bubbles:

myNPC.talkBubble(myScript, 0)

The function takes the following required parameter:

• script: (Dialog[]) This array contains the information to manage the conversation, including events that may be triggered, options to choose, etc.

It can also take the following optional parameters:

• startIndex: (number | string) The Dialog object from the script array to open first. By default this is 0, the first element of the array. Pass a number to open the entry on a given array position, or pass a string to open the entry with a name property matching that string.

To interrupt the flow of an NPC's dialog windows, you can either:

• Run .endInteraction() on the NPC
• Run .closeDialogWindow() on the NPC's bubble object
• Run .closeDialogEndAll() on the NPC's bubble object

The first two options keep running any triggeredByNext() functions associated to the dialogs being shown on the bubble, the third option prevents running these.

Play Animations

By default, the NPC will loop an animation named 'Idle', or with a name passed in the idleAnim parameter.

Make the NPC play another animation by calling the playAnimation() function. The function takes the following required parameter:

• animationName: (string) The name of the animation to play.

It can also take the following optional parameters:

• noLoop: (boolean) If true, plays the animation just once. Otherwise, the animation is looped.
• duration: (number) Specifies the duration in seconds of the animation. When finished, it returns to playing the idle animation.

Note: If noLoop is true but no duration is set, the model will stay still after playing the animation instead of returning to the idle animation.

myNPC.playAnimation(`Head_Yes`, true, 2.63)

Change idle animation

The NPC's idle animation is looped by default whenever the NPC is not playing any other animations. In some cases you may want to have different idle animations depending on the circumstances, like while in a conversation, or if the NPC changes its general attitude after some event.

You set the NPC's idle animation when creating the NPC, using the idleAnim field. To change this animation at some later time, use changeIdleAnim().

The changeIdleAnim() function takes two arguments:

• animation: The name of the new animation to set as the idle animation
• play: Optionally pass this value as true if you want this new animation to start playing right away.

myNPC.changeIdleAnim(`AngryIdle`, true)

Activate

The activate() function can be used to trigger the onActivate() function, as an alternative to pressing E or walking near.

myNPC.activate()

The activate() function is callable even when in cool down period, and it doesn't start a new cool down period.

Stop Walking

If the NPC is currently walking, call stopWalking() to stop it moving and return to playing its idle animation.

myNPC.stopWalking()

stopWalking() can be called with no parameters, or it can also be called with:

• duration: Seconds to wait before starting to walk again. If not provided, the NPC will stop walking indefinitely.

Note: If the NPC is has its dialog window open when the timer for the duration ends, the NPC will not return to walking.

To make the NPC play a different animation from idle when paused, call playAnimation() after stopWalking().

Follow Path

Make an NPC walk following a path of Vector3 points by calling followPath(). While walking, the NPC will play the walkingAnim if one was set when defining the NPC. The path can be taken once or on a loop.

followPath() can be called with no parameters if a path was already provided in the NPC's initialization or in a previous calling of followPath(). If the NPC was previously in the middle of walking a path and was interrupted, calling followPath() again with no arguments will return the NPC to that path.

myNPC.followPath()

Note: If the NPC is initialized with a path value, it will start out walking that path in a loop, no need to run followPath().

followPath() has a single optional parameter of type FollowPathData. This object may have the following optinal fields:

• path: Array of Vector3 positions to walk over.
• speed: Speed to move at while walking this path. If no speed or totalDuration is provided, it uses the NPC's walkingSpeed, which is 2 by default.
• totalDuration: The duration in seconds that the whole path should take. The NPC will move at the constant speed required to finish in that time. This value overrides that of the speed.
• loop: boolean If true, the NPC walks in circles over the provided set of points in the path. false by default, unless the NPC is initiated with a path, in which case it starts as true.
• curve: boolean If true, the path is traced a single smooth curve that passes over each of the indicated points. The curve is made out of straight-line segments, the path is stored with 4 times as many points as originally defined. false by default.
• startingPoint: Index position for what point to start from on the path. 0 by default.
• onFinishCallback: Function to call when the NPC finished walking over all the points on the path. This is only called when loop is false.
• onReachedPointCallback: Function to call once every time the NPC reaches a point in the path.

export let myNPC = new NPC({ position: new Vector3(2, 0, 2) }, 'models/CatLover.glb', () => {
  log('NPC activated!')
})
myNPC.followPath({
  path: [new Vector3(2, 0, 2), new Vector3(2, 0, 4), new Vector3(6, 0, 2)],
  totalDuration: 4,
  loop: false,
  curve: true,
  startingPoint: 0,
  onFinishCallback: () => {
    log('Finished!')
  }
})

NPC Walking Speed

The following list of factors are used to determine speed in hierarchical order:

• totalDuration parameter set when calling followPath() is used over the total distance travelled over the path.
• speed parameter set when calling followPath()
• walkingSpeed parameter set when initializing NPC
• Default value 2.

Joining the path

If the NPC's current position when calling followPath() doesn't match the first position in the path array (or the one that matches the startingPoint value), the current position is added to the path array. The NPC will start by walking from its current position to the first point provided in the path.

The path can be a single point, and the NPC will then walk a from its current position to that point.

Note: If the speed of the NPC is determined by a totalDuration value, the segment that the NPC walks to join into the path is counted as part of the full path. If this segment is long, it will increase the NPC walking speed so that the full path lasts as what's indicated by the totalDuration.

In this example the NPC is far away from the start of the path. It will first walk from 10, 0, 10 to 2, 0, 2 and then continue the path.

export let myNPC = new NPC({ position: new Vector3(10, 0, 10) }, 'models/CatLover.glb', () => {
  log('NPC activated!')
})
myNPC.followPath({
  path: [new Vector3(2, 0, 2), new Vector3(4, 0, 4), new Vector3(6, 0, 6)]
})

Example Interrupting the NPC

In the following example, an NPC starts roaming walking over a path, pausing on every point to call out for its lost kitten. If the player activates the NPC (by pressing E on it or walking near it) the NPC stops, and turns to face the player and talk. When the conversation is over, the NPC returns to walking its path from where it left off.

export let myNPC = new NPC(
  { position: new Vector3(10, 0.1, 10) },
  'models/CatLover.glb',
  () => {
    myNPC.stopWalking()
    myNPC.talk(lostCat, 0)
  },
  {
    walkingAnim: 'walk',
    walkingSpeed: 3,
    faceUser: true
  }
)
myNPC.followPath({
  path: [new Vector3(4, 0, 30), new Vector3(6, 0, 29), new Vector3(15, 0, 25)],
  loop: true,
  onReachedPointCallback: () => {
    myNPC.stopWalking(3)
    myNPC.playAnimation(`Cocky`, true, 2.93)
  }
})

export let lostCat: Dialog[] = [
  {
    text: `I lost my cat, I'm going crazy here`
  },
  {
    text: `Have you seen it anywhere?`
  },
  {
    text: `Ok, I'm gonna go back to looking for it`,
    triggeredByNext: () => {
      myNPC.followPath()
    },
    isEndOfDialog: true
  }
]

End interaction

The endInteraction() function can be used to abruptly end interactions with the NPC.

If applicable, it closes the dialog UI, hides speech bubbles, and makes the NPC stop rotating to face the player.

myNPC.endInteraction()

As an alternative, you can call the handleWalkAway() function, which has the same effects (as long as continueOnWalkAway isn't set to true), but also triggers the onWalkAway() function.

NPC Dialog Window

You can display an interactive dialog window to simulate a conversation with a non-player character (NPC).

The conversation is based on a script in JSON format. The script can include questions that can take you forward or backward, or end the conversation.

The NPC script

Each entry on the script must include at least a text field, but can include several more fields to further customize it.

Below is a minimal dialog.

export let NPCTalk: Dialog[] = [
  {
    text: 'Hi there'
  },
  {
    text: 'It sure is nice talking to you'
  },
  {
    text: 'I must go, my planet needs me',
    isEndOfDialog: true
  }
]

The player advances through each entry by clicking the mouse button. Once the last is reached, clicking again closes the window, as it's marked as isEndOfDialog.

The script must adhere to the following schema:

class Dialog {
  text: string
  name?: string
  fontSize?: number
  offsetX?: number
  offsetY?: number
  typeSpeed?: number
  isEndOfDialog?: boolean
  triggeredByNext?: () => void
  portrait?: ImageData
  image?: ImageData
  isQuestion?: boolean
  isFixedScreen?: boolean
  buttons?: ButtonData[]
  audio?: string
  skipable?: boolean
}

Note: A Dialog object can be used as an input both for the talk() function (that is displayed in the UI), and the talkBubble() function (that is displayed in a floating bubble over the NPC). Properties marked with * are only applicabe to UI dialogs.

You can set the following fields to change the appearance of a dialog:

• text: The dialog text
• fontSize: Size of the text
• offsetX *: Offset of the text on the X axis, relative to its normal position.
• offsetY *: Offset of the text on the Y axis, relative to its normal position.
• portrait *: Sets the portrait image to use on the left. This field expects a Portrait object.
• image *: Sets a second image to use on the right of the dialog, and slightly up. This field expects an ImageData object.

The ImageData required for the portrait and image fields, may include the following:

• path: Path to the image file.
• xOffset: Offset on X, relative to the normal position of the image.
• yOffset: Offset on Y, relative to the normal position of the image.
• width: The width to show the image onscreen.
• height: The height to show the image onscreen.
• section: Use only a section of the image file, useful when arranging multiple icons into an image atlas. This field takes an ImageSection object, specifying sourceWidth and sourceHeight, and optionally also sourceLeft and sourceTop.

Other fields:

• name: Optionally add a name to an entry, this serves to more easily refer to an entry.
• buttons *: An array of buttons to use in a question entry, covered in the next section.
• audio: String with the path to an audio file to play once when this dialog is shown on the UI.
• typeSpeed: The text appears one character at a time, simulating typing. Players can click to skip the animation. Tune the speed of this typing (30 by default) to go slower or faster. Set to -1 to skip the animation.
• skipable *: If true, a "Skip" button appears in the corner to let players jump to the next non-skipable dialog, or close the dialog. Question dialogs can't be skiped.

Add format tags within the text string to accentuate parts of the text.

• Use <b></b> for bold
• Use <i></i> for italics
• Use <color="red"></color> to color text

For example:

export let NPCTalk: Dialog[] = [
  {
    text: 'This is <b>BOLD</b>'
  },
  {
    text: 'This is <i>italic</i>'
  },
  {
    text: 'This is <color="red">red</color>',
    isEndOfDialog: true
  }
]

Questions and conversation trees

The script can include questions that prompt the player to pick between two or up to four options. These questions can branch the conversation out and trigger other actions in the scene.

Note: Questions are only used by UI dialogs. If used in a speech bubble, questions will be displayed as regular entries with no buttons or options.

To make an entry a question, set the isQuestion field to true. This displays a set of buttons rather than the click icon. It also disables the click to advance to the next entry.

The buttons property of an entry contains an array of ButtonData objects, each one of these defines one button.

When on a question entry, you must provide at least the following for each button:

• label: (string) The label to show on the button.
• goToDialog: (number | string) The index or name of the next dialog entry to display when activated.

TIP: It's always better to refer to an entry by name, since the array index might shift if you add more entries and it can get hard to keep track of these references.

You can also set the following:

• triggeredActions: ( () => void ) An additional function to run whenever the button is activated
• fontSize: (number) Font size of the text
• offsetX: (number) Offset of the label on the X axis, relative to its normal position.
• offsetY: (number) Offset of the label on the Y axis, relative to its normal position.

All buttons can be clicked to activate them. Additionally, the first button in the array can be activated by pressing the E key. The second button in the array can be activated by pressing the F key,

export let GemsMission: Dialog[] = [
  {
    text: `Hello stranger`
  },
  {
    text: `Can you help me finding my missing gems?`,
    isQuestion: true,
    buttons: [
      { label: `Yes!`, goToDialog: 2 },
      { label: `I'm busy`, goToDialog: 4 }
    ]
  },
  {
    text: `Ok, awesome, thanks!`
  },
  {
    text: `I need you to find 10 gems scattered around this scene, go find them!`,
    isEndOfDialog: true
  },
  {
    text: `Ok, come back soon`,
    isEndOfDialog: true
  }
]

Triggering functions from the dialog

You can run functions that may affect any other part of your scene. These functions get triggered when the player interacts with the dialog window, or when the NPC displays speech bubbles.

• triggeredByNext: Is executed when the player advances to the next dialog on a non-question dialog. The function also gets called if the dialog is the end of the conversation. It also gets called when a speech bubble advances to the next entry.

• triggeredActions: This property is associated to a button and is executed on a question dialog if the player activates the corresponding button. You can have up to 4 different buttons per entry, each with its own actions.

export let GemsMission: Dialog[] = [
  {
	text: `Hello stranger`,
	triggeredByNext: () => {
		// NPC plays animation to show a gem
	}
  },
   {
    text: `Can you help me finding my missing gems?`,
	isQuestion: true,
	buttons: [
	  {
		label: `Yes!`,
		goToDialog: 2,
		triggeredActions:  () => {
			// NPC plays an animation to celebrate
		}
	  },
	  {
		label: `I'm busy`,
		goToDialog: 4
		triggeredActions:  () => {
			// NPC waves goodbye
		}
	  },
	]
  },
  {
    text: `Ok, awesome, thanks!`,
  },
  {
	text: `I need you to find 10 gems scattered around this scene, go find them!`,
	isEndOfDialog: true
	triggeredByNext: () => {
		// Gems are rendered all around the scene
	}
  },
  {
	text: `Ok, come back soon`,
	isEndOfDialog: true
  }
]

Skipping Dialogs

Each dialog has an optional skipable property. If true, a button appears in the bottom-left corner of the dialog window. Players can click this button or press F to skip all the following dialogs.

When skipping, players will jump forward in the conversation till

• They reach a dialog that doesn't have the skipable property.
• They reach a dialog with isQuestion=true.
• They reach a dialog that has the skipable property and isEndOfDialog, in which case the dialog window is closed.

No-NPC Dialogs

You can open a Dialog window that isn't associated with any NPC object in the scene. The DialogWindow object has all the same functionality as calling the talk() function on an NPC, but may be more practical in scenarios where a character isn't physically there, or where the conversation isn't with a particular character.

The Dialog window

To create a new dialog window, create a new DialogWindow object. This will instantiate the window but keep it hidden until you open it.

let dialogWindow = new DialogWindow()

When instantiating a new DialogWindow, you can pass the following parameters:

• defaultPortrait: Sets a default portrait image to use on the left of all dialogs that don't specify an image. If a dialog has no portrait and no default is provided, no image is shown on the left. This field expects a Portrait object, that may include the following fields: - path: Path to the image file - xOffset: Offset on X, relative to the normal position of the portrait. - yOffset: Offset on Y, relative to the normal position of the portrait. - section: Use only a section of the image file, useful when arranging multiple icons into an image atlas. This field takes an ImageSection object, specifying sourceWidth and sourceHeight, and optionally also sourceLeft and sourceTop.
• useDarkTheme: Switch the style of the window to the dark theme.
• sound: Path to a sound file that will be played once for every dialog entry shown, as long as the dialog entry doesn't have its own audio property.

Once a DialogWindow object is instanced, you can open a dialog window with the openDialogWindow() function.

dialogWindow.openDialogWindow(NPCTalk, 0)

When calling this function, you must specify:

• NPCScript: A JSON object composed of an array of Dialog objects, that includes all the dialog tree.

A second optional parameter is also available:

• textId: The index or name property of the entry to show first from the script. The first entry is 0.

TIP: It's always better to refer to an entry by name, since the array index might shift if you add more entries and it can get hard to keep track of these references.

Close a dialog window at any time by calling the closeDialogWindow() function.

dialogWindow.closeDialogWindow()

For details on how to construct the dialog tree, see the sections above. The required NPCScript by the DialogWindow has exactly the same characteristics as the one used on the NPC object when calling the talk() function.

---

Contribute

In order to test changes made to this repository in active scenes, do the following:

1. Run npm run build for the internal files of the library to be generated
2. Run npm run link on this repository
3. On a new Decentraland scene, import this library as you normally would and include the tests you need
4. On the scene directory, run npm link @dcl/npc-scene-utils

Note: When done testing, run npm unlink on both folders, so that the scene stops using the local version of the library.

CI/CD

This repository uses semantic-release to atumatically release new versions of the package to NPM.

Use the following convention for commit names:

feat: something: Minor release, every time you add a feature or enhancement that doesn’t break the api.

fix: something: Bug fixing / patch

chore: something: Anything that doesn't require a release to npm, like changing the readme. Updating a dependency is not a chore if it fixes a bug or a vulnerability, that's a fix.

If you break the API of the library, you need to do a major release, and that's done a different way. You need to add a second comment that starts with BREAKING CHANGE, like:

commit -m "feat: changed the signature of a method" -m "BREAKING CHANGE: this commit breaks the API, changing foo(arg1) to foo(arg1, arg2)"