UnrealGDK Snapshot Migrator

Note that this plugin is marked as beta and should be considered to be an experimental work in progress.

This plugin (for use with Unreal Engine 4 and the SpatialOS GDK for Unreal) provides a means to migrate the contents of a set of snapshots between one version of schema and another.

Requirements

• Unreal Engine 4.24 (or greater)
• SpatialOS GDK for Unreal 0.9 (or greater)

Installation

1. Download this plugin to either plugin folder (Engine/Plugins or Game/Plugins)
2. Add the SPATIALGDK_API tag to USpatialReceiver's class definition (in SpatialGDK/Source/SpatialGDK/Public/Interop/SpatialReceiver.h)
   • This is currently required in order to allow instantiation of the SpatialReceiver in the Migrator; this is hopefully temporary
3. In DefaultSnapshotClasspathWhitelistPatterns.ini, replace {ProjectName} with your project's name.
   • This config file is used to gate which entities are migrated in a snapshot; if an entity represents an Unreal Actor it will only be migrated if its classpath matches one of the patterns in this file.
4. Move DefaultSnapshotClasspathWhitelistPatterns.ini to your project's config folder (Game/Config)

Usage

The migrator requires three pieces of data to work:

1. The snapshots you want to migrate; these are your source snapshots
2. A schema json bundle representing the schema used when the snapshots you want to migrate were generated; this is the source bundle.
3. A schema json bundle representing your current schema; this is the target bundle.

Schema json bundles can be obtained by invoking the Schema Compiler with the --bundle_json_out argument; if you are using the CookAndGenerateSchema commandlet provided by the GDK, you can pass this argument through to the compiler by invoking the commandlet with -AdditionalSchemaCompilerArgs="--bundle_json_out=\"{path/to/bundle.sb.json}\"".

The Snapshot Migrator is currently implemented as a commandlet and can be invoked as any other UE4 commandlet can. E.g., from the commandline: path/to/UE4/Engine/Binaries/Win64/UE4Editor-Cmd.exe path/to/UE4/{Project}/Game/{Project}.uproject -Run=SnapshotMigrator

By default, the migrator will expect to find the source snapshots and the source bundle at {project spatial dir}/tmp/artifacts and the target bundle at {project spatial dir}/build/assembly/schema. This can be overridden by passing -OldArtifactsDir or -CompiledSchemaDir, respectively.

For a visual, high-level overview of how the migrator works, please see the entity migration flow and snapshot migration flow diagrams.