RimWorld is moving off Unity, with update 1.7 putting the colony simulation on the Waylith Engine, an in-house engine built by developer Ludeon Studios. The studio says the game will look and play exactly as before.
The reason to care is speed. Tests at Ludeon put the gain at 2x to 4x, with faster startup, map generation, world generation and ticks per second. A stress test of a late-game colony ran 2.2 times faster on 1.7 than on 1.6, and a modpack of 1,500 mods dropped from 14 minutes to 6 minutes to load. Ludeon cautions that results depend on each player's PC and mod list.
Compatibility decides whether modded players will follow, and the studio's answer is that the move can be reversed. Saves from 1.6 load on 1.7, and 1.7 saves load again if a player drops back to 1.6. Ludeon says the vast majority of mods run unchanged. Some will show a yellow "potentially unsupported" flag only because the version number changed, and authors are asked to publish a build marked 1.7-compatible to clear it.
Older hardware is the exception. Ludeon warns that a PC more than 10 years old may not run the new version, and asks affected players to report it on the development Discord, where the studio says it may make changes to help. Modders get newer C# language features and, according to Ludeon, an easier path to complex mods and custom visual effects without a performance penalty. More than two dozen modders tested the engine before the announcement.
Players can try 1.7 now on the unstable beta branch in Steam, found under the Betas tab in RimWorld's properties. The default branch stays on 1.6, and no date for the stable release has been given. Waylith is also not exclusive to RimWorld: Ludeon says it is working on a new game on the engine and shared nothing more.
RimWorld's heavy mod use makes it a demanding first customer for any engine, so the 1,500-mod load time is the figure to watch once the beta reaches the wider community.
