Note: This content is intended as a companion to the tutorial world of the same name, which you can access through the desktop editor. When you open the tutorial world, a copy is created for you to explore and leverage, and this page is opened so that you can follow along. For more information, see Access Tutorial Worlds.

When building in Meta Horizon Worlds, you can introduce objects into your world by adding them from your set of assets or spawning them into your world during gameplay. This tutorial covers different techniques of spawning and pooling of objects.

Spawning refers to adding in assets to the world experience at runtime. Spawning is supported through multiple methods. Each method has trade-offs in terms of performance and resources. For more general information on asset spawning, see Introduction to Asset Spawning.

This world provides specific examples of asset spawning and also includes an example of object pooling, which allows you to pre-load instances of assets in the world and then deploy them into the space as needed.

Note: Included in the code is a useful Pool class, which can be extracted from the script files and adapted for your own use.

TypeScript v2.0.0 introduced a dedicated container object for managing spawning and pooling. The Spawn Controller object is covered in the third station in the world.

If you haven’t done so, please review the Getting Started section for tutorials, which includes information on:

Note: All tutorials are created using TypeScript 2.0.0.

See Getting Started with Tutorials.

To explore the world described in this tutorial, you must make a personal copy of the Spawning and Pooling in TypeScript tutorial world.

In desktop editor:

When you create a new world in the desktop editor, you can create it based on the Spawning and Pooling in TypeScript tutorial world. For more information, see Access Tutorial Worlds.

In headset:

Note: This world is not a beginner’s world. This world requires understanding of TypeScript.

Before you begin this tutorial, you should have already completed a worldbuilding tutorial or have begun building your own worlds.

For more information, see Tutorial Worlds.

In theory, you can add every asset that your world needs as entities in the world. It’s possible to add in each sound, gizmo, enemy, visual effect that is needed for each part of the overall world experience. However, you can quickly run into problems:

For optimal resource management in worlds of sufficient complexity, it’s best to implement object spawning and object pooling, which enable you to bring in entities when needed and to discard them when they are not.

This world contains three separate stations, each of which is described in the following modules. Each station demonstrates a separate method for handling spawning and despawning, listed below in order of increasing complexity and efficiency of use.

Station 1 - Object spawning: Spawn/despawn each instance of an asset as it is needed.

Station 2 - Object pooling: Spawn assets at world start into an off-screen pool, from which entities can be moved into the play area to “spawn” them and moved back to the pool for “despawning.”

Station 3 - SpawnController: This innovation of TypeScript v2.0.0 allows you to preload assets into an array of SpawnController objects.

Tip: SpawnController is the recommended method for managing spawned assets.

Each method spawns in 100 instances of the same small asset.

Object spawning and despawning allow creators to instantiate and destroy objects at runtime through scripts. These objects are tied to assets pulled from assets to which the world owner has access, and enables you to spawn various objects for users to interact with, to perform actions in-world, and then remove them when they are no longer needed.

Tip: For best results, you should create a shared folder for storing spawned assets or assets that are to be used across a multi-person team. See Shared Folders.

Before adding object spawning to a world, here are a few questions you should consider:

The answers to these questions can inform a decision if object spawning and despawning benefits or detracts from your world’s experience.

Note: Spawning and despawning has a performance cost at runtime, especially when objects are spawned in succession. Ideally, spawned assets are managed outside of core gameplay periods.

To address the costs of spawning and despawning, object pooling is a design pattern in which objects needed during gameplay are pre-instantiated before gameplay begins. Object pooling enables you to optimize your worlds and reduce the CPU costs when having to regularly create/destroy objects during gameplay, resulting in smoother gameplay experience.

TypeScript API v2.0.0 introduced the SpawnController object, which is a container for spawned assets. Using SpawnControllers, you can pre-load a pool of assets into runtime memory at world start. These loaded objects are not immediately part of the world, and you do not have to manage them within the runtime world experience until they are needed.

When they are needed, the spawn() method makes the entities part of the world experience. When they are no longer needed, you use the unload() method to move them out of the world yet retain them in runtime memory. After they have been loaded, they can be quickly flipped in and out of the runtime experience, for faster and smoother gameplay.

Considerations:

Tip: For best results, you should create a shared folder for storing spawned assets or assets that are to be used across a multi-person team. See Shared Folders.

Each station features robust logging to the console. When the world is first started, the numerous logging messages allow you to track the loading and spawning processes of each one; you can see that initialization is not fast and immediate and is not synchronous.

However, you may decide that you want to disable the extensive logging. You can disable logging for individual stations by setting the following variables to FALSE in the appropriate script: