Last year’s Assassin’s Creed Shadows was built on the power of the Anvil engine , one of Ubisoft’s proprietary technologies that enables developers to build rich, dynamic worlds at scale. Behind the scenes, teams across Ubisoft continuously evolve Anvil’s tools and systems to push the boundaries of what’s possible in real time.

For Assassin’s Creed Shadows, close collaboration between production teams and Anvil developers led to a number of innovations designed to bring the world of 16th-century Japan to life with unprecedented depth. From dynamic weather systems to advanced rendering techniques, each breakthrough is built with one goal in mind: turning cutting-edge technology into something players can see, feel, and experience.

Let’s take a look under the hood with the developers behind these innovations to see how Anvil created the immersive and dynamic world of Assassin’s Creed Shadows.

Atmos – Creating Realistic Weather

Atmos is the name of a group of systems that manage simulating weather in the Anvil engine. These systems add up to an entire network of real-time environmental control and a breathtaking world that can flip from a bright and sunny spring day, to dark and stormy, to a snowy winter wonderland on a dime. The system can control rainfall, windspeed, and direction, and even precipitation and cloud cover, resulting in a finely tuned variety of different weather patterns. And each environmental element can interact with the other to produce stunning results – wind blowing rain that drips off the eaves of a building onto characters’ clothes and hair, bright rays of sun beaming through the canopy of a forest, drying up puddles and evaporating the water into clouds that are moved by the wind. It creates a realistic climate which gives every location a unique character that changes with every visit through the days and seasons , and builds a strong sense of immersion as wind, rain, and snow all act in realistic and believable ways.

“Through a constantly evolving mood, Atmos draws players into a living world that enriches every moment of their experience,” says Maxime Beaudoin, Technical Lead. “It really enhances the environment and creates a more immersive universe for players to explore and lose themselves in.”

Building Scalable Worlds –Seamless Exploration on Every Platform

Assassin’s Creed Shadows features a sprawling, intricately detailed world. The team’s goal was to keep gameplay fluid and immersive even at such an impressive scale, while ensuring the game runs smoothly across a variety of platforms.

To achieve this, the team developed systems that deliver high-quality visuals while maintaining smooth gameplay across a variety of hardware – from the most powerful PCs to the latest consoles. Innovations in loading distance and automated adaptive geometry allow distant towns, mountains, and other landmarks to appear seamlessly, preserving continuity and immersion. The result is a world that invites exploration and lets players fully appreciate the scope of their surroundings without ever noticing technical boundaries, no matter the platform.

“Large-scale rendering truly shines in Assassin’s Creed Shadows,” says Anvil Technical Architect Nicolas Lopez. “My favorite example is Azuchi Castle. It sits on elevated terrain overlooking a large landscape with visible layers of clouds, fog, water, and distant cities. The lighting conditions at sunset with sunlight scattered through atmosphere and reflecting off different surfaces combine with verticality to create a strong sense of scale and depth. It’s one of those moments where everything aligns to create a powerful sense of awe.”

Micropolygon Geometry – Looking Good at any Distance

Games have a data budget, meaning that there can only be a certain number of polygons (the shapes that form a "web" and create the geometry of an object) shown on screen before the hardware starts to struggle with loading. This can lead to a variety of issues such as low framerates, objects suddenly "popping" into or out of existence, or low-quality textures and models appearing where they shouldn’t. Traditionally, games will feature a range of different quality textures and models that will be loaded at different distances – you don’t need to see the highest detail on that house that’s two miles away as you would when it’s right in front of you. This takes time, as an artist needs to create each version of the object to be loaded in, and a programmer needs to define when and how those objects load. Micropolygon geometry really changes the game, literally! Born from years of research and development, this system frees up developers to create high-quality versions of assets while automated systems lower resolution and detail dependent on distance to create a seamless and smooth experience for players, so they can explore the world without ever knowing it’s happening.

“Micropolygon technology allows pixel-precise model quality similar to movie quality,” says Lionel Berenguier, Anvil Technical Lead. “It allows us to avoid objects ‘popping’ or suddenly changing quality levels and produces a smoother result. It’s more advanced than previous blending techniques that are standard in gaming. Additionally, it frees up artists from the grunt work of generating these models and tweaking them, allowing them to focus on refining the visuals, and that has a big impact on the final result and the player experience.”

Raytraced Global Illumination – Making the World Shine

Lighting is absolutely key to creating a dynamic and believable world. Most of us intuitively have a very strong concept of how light works and reacts in the environment, so creating more dynamic lighting really brings a world closer to reality. That’s where raytraced global illumination comes in. Through a series of different layers and systems, the Anvil team simulated far more realistic behaviors for the millions of light rays being generated in Assassin’s Creed Shadows. In the past, light was "baked" into a scene, meaning an artist would define where light fell on a scene, and it wouldn’t change. With Assassin’s Creed Shadows, lighting is dynamic and changes over the course of the day, differing with each season, interacting and affecting every pixel on the screen. The team also implemented unique systems that would simulate the way light scatters through the iconic paper doors used in Japan, diffusing and scattering light that shines through them. Give it a try – open a door and see the room flood with light, close it again and watch as it diffuses through the paper and the whole scene changes.

“Raytraced Global Illumination makes lighting fully reactive to gameplay,” said Nicolas Lopez. “Lights can be turned off or destroyed, and the entire scene updates accordingly. That makes shadows more natural and improves stealth readability. It also makes the world more believable, as lighting adapts consistently to weather, time of day, and seasons.”

Anvil continues to grow and evolve with each game it powers, with systems and techniques being developed to bring an even deeper level of immersion and heighten the player experience. If you want to check out the innovations being built by the teams behind Anvil and across Ubisoft, keep an eye for future announcements in Assassin’s Creed and other series, or pick up Assassin’s Creed Shadows now on Ubisoft+, PlayStation 5, Xbox Series X|S, Nintendo Switch 2, PC through the Ubisoft Store, Epic Games Store, & Steam, and on Mac.