Prefab Basics

Understanding and creating prefabs is essential for any Subnautica mod that adds new content. This page will provide basic information on how prefabs are used in Subnautica and why they are important.

What Are Prefabs?

At the most basic level, prefabs are simply stored GameObjects that can be instantiated into a scene. This is a Unity Engine concept, and it applies for Subnautica modding as well.

In Subnautica, prefabs encompass essentially anything that exists in the world, aside from terrain, the player, and a few other exceptions. This includes anything from creatures to base modules to fragments to unnamed rock formations and debris. They are registered and managed by the UWE.PrefabDatabase class. Nautilus allows you to indirectly register your own custom prefabs into this system.

Subnautica prefabs consist of the following:

Class ID (defined in the GameObject's PrefabIdentifier component)
TechType (this is actually optional, and is defined in the GameObject's TechTag component)
The actual GameObject that is spawned.

Differences Between Class ID and TechType

These are two distinct identification systems used by the game and should not be conflated.

Class ID

The Class ID is the only thing that is required for a prefab. A mod that adds new commands such as DebugHelper is required to actually spawn a prefab by its Class ID. All base-game Class IDs are 36-character-long GUIDs. When you create a prefab with Nautilus, the Class ID will use the TechType name by default. You can find a list of all Class IDs here.

TechType

TechTypes are more easily accessible without external resources, and are often far more readable. You may recognize them from the spawn command. Unlike Class IDs, which aren't readily available, TechTypes are all listed under the TechType enum in the game's codebase. There are thousands of prefabs that cannot be spawned with the spawn command because they don't have a TechType assigned. Having a TechType is required for crafting recipes, blueprints, inventory items, and more.

A screenshot of the first 22 values of the decompiled TechType enum

Most importantly: there can be multiple prefabs with the same TechType, but every prefab has a different Class ID. This is why you can have multiple fragments with different models that unlock the same blueprint. Each fragment would have the same TechType, but a unique ClassID.

Essential Components

There are a few components that are required or heavily recommended for prefabs. The PrefabUtils.AddBasicComponents method provided by Nautilus handles most of this for you. You can also set up these components in the Unity Editor if using Thunderkit.