Yesterday, Ubisoft kicked off a behind-the-scenes video series dedicated to its Anvil Engine, which is mainly used to make the company's Assassin's Creed franchise.
The latest iteration of the saga, Assassin's Creed Shadows, introduced several technological improvements that made it a stunning technical showcase upon release. With this behind-the-scenes video series, Ubisoft aims to delve into the key innovations introduced to Anvil, starting with Atmos.
Atmos is Ubisoft's physically based weather simulation system built into the Anvil engine for Assassin's Creed Shadows. Rather than using pre-baked or downloaded weather states, it simulates atmospheric conditions in real time, propagating physical quantities such as temperature, vapor, and humidity to dynamically determine weather outcomes: whether it's raining, windy, or clear in any given location.
At its core, Atmos runs a fluid simulation that drives multiple interconnected systems simultaneously. Wind simulation is the central driver because it feeds into cloud generation, precipitation, and everything else. Separately, the team developed a spray particle system: a dynamic wind simulation with collision that physically carries particles across the environment. The key point they emphasize is that wind data is shared across all systems, so rain, character clothing, hair, foliage, sound, and lighting all respond to the same underlying simulation coherently rather than independently.
Gameplay and Visual Impact
According to the developers, Atmos doesn't just affect visuals but also NPCs, animals, crowds, and gameplay possibilities in real time. Weather transitions happen seamlessly without loading, a feature the team reveals as unprecedented in the Assassin's Creed franchise. In the video, Ubisoft noted that player feedback and reviews showed many players were avoiding fast travel because they didn't want to miss dynamic weather transitions during overland travel.
The team describes Atmos as acting like a maestro. It doesn't own every system, but it orchestrates all of them (rain, lighting, sound, particles) into a coherent whole. The goal was coherence as a pillar of immersion: wind blows rain onto character models, moves clothes, tousles hair, all driven by the same simulation data.
The video ends with a tease:
It's only just the beginning. Anvil will keep pushing the boundaries of immersion and open world design to the benefit of you, the players.
Indeed, the timing of this Anvil Engine behind-the-scenes series is a bit curious. Assassin's Creed Shadows is now firmly in the rearview, with Ubisoft confirming that there are no further DLCs planned after Claws of Awaji.
One possible explanation is the long-awaited remake Assassin's Creed IV: Black Flag Resynced, which will also be powered by the latest version of the Anvil Engine and should therefore include all of its features, including Atmos. According to rumors, Resynced should be revealed very soon.
About the author: With over two decades of experience in gaming journalism, Alessio Palumbo has led the gaming vertical at Wccftech since August 2015. He started working at a young age for Italian websites like Everyeye.it, Gamestar.it, Nextgame.it, and Multiplayer.it before kickstarting the indie English-language publication Worlds Factory as its founder and Editor in Chief. In the last decade, he has coordinated the overall output of Wccftech's gaming section, managed PR relations, assigned reviews, produced daily news coverage, edited gaming content as needed, and delivered game reviews. Arguably, his trademark content is the long series of exclusive developer interviews that have been cited by Wikipedia and by the biggest news media and gaming publications. His passion for technology also makes him knowledgeable when it comes to gaming hardware and tech. His favorite genres include RPGs, MMORPGs, and action/adventure games.
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