Skip to content

Runtime Assemblies

The CAT Assembly Actor is the standard world entry point. Its Assembly Component owns the authoritative runtime state.

Initialize from an authored asset

Assign a Part Model or Assembly Asset to Source Asset. On authority, the actor loads the source into its Assembly Component during BeginPlay.

Use one of these Blueprint functions when initialization must happen explicitly:

  • Initialize From Source Asset
  • Initialize From Part Model Asset
  • Initialize From Assembly Asset

Enter simulation

Auto Enter Simulation is enabled by default. Disable it only when gameplay must prepare or modify the assembly before physics begins.

Manual flow:

Initialize or Load
      ↓
Validate the result
      ↓
Enter Simulation

Save and load at runtime

Use the Assembly Component to store or restore a live Assembly.

  • Build Save Data creates Assembly data for the project's own save system.
  • Save Assembly To Cat Assembly File writes a CAT save file.
  • Load From Save Data and Load Assembly From Cat Assembly File restore an existing Assembly Actor.
  • Request Spawn And Load Cat Assembly File asks the player-owned Assembly Interactor Component to spawn a new Assembly Actor and load a file into it.

Loading and spawning must run with server authority. Check the returned result before continuing, and handle missing Part Models or incompatible save versions.

Query the runtime

Prefer object-based APIs:

  • Get Parts returns CAT Part objects.
  • Get Relations returns CAT Relation objects.
  • CAT Part provides its Connectors, Actuators, and related Parts.
  • Hit Results can be resolved back to the owning CAT Part and Body ID.

Legacy View-based connector and relation queries are deprecated.

Change structure

Create commands with the CAT Assembly Blueprint Library, validate with Can Execute Command, and submit through an Assembly Interactor Component or execute on authority.

Authority

Loading, structural commands, and authoritative full-state installation must run on standalone or server authority.