The game runs on an enhanced build of the Anvil engine.
According to the lead programmer on Assassin’s Creed Shadows, the development team essentially had to rebuild the world’s rendering pipeline and even revise how core game systems interact in order to bring the title to the Nintendo Switch 2.
Key simulations (such as volumetric clouds and cloth physics) were retained but extensively optimized and partly simplified to lower GPU load. Global illumination relies on a precomputed solution—similar to what is used on lower-end PCs and the Xbox Series S—rather than hardware ray tracing, which conserved video memory.
Additionally, the team manually tuned nearly every parameter for each location: draw distance, level-of-detail thresholds, texture resolutions, and the density of streamed objects. NPC counts were only reduced in the most congested urban areas, and only to the degree necessary to preserve stable performance.
To improve performance the game supports NVIDIA DLSS — it is rendered at a lower internal resolution and then upscaled and reconstructed to a crisp final image. As a result, Ubisoft achieved a consistent 30 frames per second in both handheld and docked modes.
Ubisoft also developed a custom algorithm to take full advantage of VRR, which helps the presentation feel smooth even at 30 fps.
Source: iXBT.games