We at CD Projekt Red are collaborating with Epic Games to push open-world game design further than ever before, and we wanted to share our progress with the gaming community through The Witcher 4 Unreal Engine 5 Tech Demo—a showcase of how we're bringing more life, depth, and reactivity to the Continent than ever before. This isn't gameplay of The Witcher 4, but we still wanted to incorporate CD Projekt Red's signature storytelling into the tech demo, showing our new protagonist Ciri in the midst of a dangerous monster contract. We also reveal the never-before-seen region of Kovir, a rugged land where cities are built on trade and keep a careful distance from the military conflicts that plague the rest of the north.

But the focus of this tech demo is just that—tech—and we were proud to show it live on stage, running at 60 frames per second on a PlayStation 5. The tools highlighted won't just power The Witcher 4, but will also be shared with the wider video game development community through Unreal Engine 5. The tech we're creating with Epic will benefit the entire industry, ultimately bringing a better experience to players.ML Deformer
Early in the tech demo we introduce Ciri's horse Kelpie to the world—and how she's far more complex than our old friend Roach. Alongside tech that makes controlling Kelpie feel much more grounded and lifelike, we've worked hard to develop high-quality, real-time character deformations.


ML Deformer allows elements like Kelpie's muscles to move and flex accurately, thanks to high-fidelity data providing it with the ability to approximate complex deformations efficiently during gameplay. This allows these incredibly realistic movements to take place without the game taking a performance hit.Fast Geometry Streaming
We're paying attention to the large scale too. Fast Geometry Streaming allows everything in the tech demo—from the snowy mountaintops to the deep valleys and vast forests—to seamlessly load without compromising performance. It's present throughout the tech demo, and the fact it can't be noticed proves it's doing its job.

Consider when we catch up with Ciri before she reaches the bustling trading hub of Valdrest, for example. We move quickly through the world, in and around different elements of the environment, but there's no stuttering or object pop-ins. Fast Geometry Streaming is optimized to quickly load static geometry, using a lightweight method to register and unregister assets. The result is what we show throughout the tech demo: smooth and seamless world loading that allows the beauty of Kovir to shine.

Nanite Foliage
Speaking of Kovir, we take a detour through one of its dense forests while Ciri is riding to Valdrest. Nanite Foliage technology we're developing with Epic allows our developers' artistic vision to be fully realized in Unreal Engine 5. This tech renders incredibly detailed and realistic trees and vegetation in terms of both density and fidelity, without compromising performance.Nanite Foliage is a new technology that efficiently renders vast amounts of foliage at runtime, making it possible to effortlessly populate landscapes with complex assets—such as lush trees with individual branches that sway in the wind.

Unreal Animation Framework
We always want to make our open worlds feel alive and lived in, and the Unreal Animation Framework shown off in the tech demo lets us add more life than ever to the villages, towns, and cities of the Continent. This tech powers advanced blending, state machines, and procedural animation workflows, letting us have many complex characters interacting with the world at once.When we place a band on the stage in Valdrest, for example, we utilize Unreal Animation Framework to drastically increase the number of NPCs on screen. And these aren't just simple onlookers standing still or operating on a loop; each one reacts to what's going on around them. We want the gap between Ciri and the NPCs of The Witcher 4 to be as small as possible.

Mass Framework
Another tool that adds to the believability and lived-in feeling of the world, Mass Framework simulates large crowds and AI behaviour like the ones seen in the busy market of Valdrest. The data-driven design of Mass manages thousands of agents with minimal performance cost, making it ideal for creating realistic, dynamic populations in games.

It also allows smart objects and complex interactions to function. As Ciri approaches the market we see her bump into a man carrying a crate of apples, for example. Notice how he doesn't just react to her collision; he loses his footing and drops several apples, which roll down the hill and trigger further, unscripted chain reactions like children running to steal one or pigs looking for an early lunch. Implementing interactions like these is one way we're making The Witcher 4 the most immersive Witcher game to date.

• Sebastian Kalemba, Game Director, The Witcher 4