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Use the Trigger zone

The Trigger zone is used to trigger an event when you enter or exit a specified area.

To use the Trigger gizmo:

From the Build list, select Gizmos.

Select Trigger zone icon.

Under Hierarchy, right-click Trigger and select Rename, then rename the trigger zone to something that describes its purpose. Note: Renaming the trigger zone is optional, but it can help you keep track of what the zone is for.
While the trigger zone is selected, you can edit its parameters in the Properties panel.

Things to remember:

Each trigger can be activated by either players or objects, but not both. If Triggered By is set to Players, any player in the world will be able to activate the Trigger.
If Triggered By is set to Objects Named..., the Triggered by Objects Named field must also be filled out. This field can currently only take one name, and any object with that name will be able to activate the trigger.
Note that objects may only have one name (or one word as a name), but multiple objects can have the same name. The size of the trigger area can be adjusted by using the handles, just like the rest of the shapes.

Use the Gizmo with TypeScript

Through TypeScript, you can monitor and take action when a Trigger Zone gizmo deployed in your world has been entered or exited by a player. In your TypeScript, you can create listeners for the following CodeBlockEvents, which are specific to trigger zones.

onPlayerEnterTrigger
onPlayerExitTrigger

CodeBlockEvents are a set of events emitted from the platform for key runtime functionality, such as events based on gizmo activities.

For more information on CodeBlockEvents, see CodeBlock Events.
For API docs on CodeBlockEvents, see CodeBlockEvents.

The following script can be attached to a Trigger Zone entity that you have deployed in your world:

import * as hz from 'horizon/core';

class TriggerMe extends hz.Component<typeof TriggerMe> {

  start() {
    // this listener for the CodeBlockEvent onPlayerEnterTrigger is fired
    // when a player enters the trigger.
    this.connectCodeBlockEvent(this.entity, hz.CodeBlockEvents.OnPlayerEnterTrigger, (enteredby:hz.Player)=>{
      this.world.ui.showPopupForEveryone("You dare enter the Trigger of Doom, " + enteredby.name.get() + "?!?!", 3)
    });

    // this listener for the CodeBlockEvent onPlayerExitTrigger is fired
    // when a player exits the trigger.
    this.connectCodeBlockEvent(this.entity, hz.CodeBlockEvents.OnPlayerExitTrigger, (exitedBy:hz.Player)=>{
      this.world.ui.showPopupForEveryone("See you, " + exitedBy.name.get() + ".", 2)
    });

  }
}
hz.Component.register(TriggerMe);

The above script defines to event listeners (this.connectCodeBlockEvent), one for each CodeBlockEvent for the trigger. Since this scrpit is attached to the trigger zone entity, these listeners are triggered based on the entrance and exit of the enteredby player to the trigger zone.

In the onPlayerEnterTrigger listener, a popup is displayed for everyone in the world with a message.

In the onPlayerExitTrigger listener, a new popup is displayed for everyone in the world with a different message.