The Witcher 4 Unreal Engine 5.6 Tech Demo Is A Stunning Ray-Traced Showcase
If you've ever played a video game based on Unreal Engine 5 and grumbled about the poor performance of it, we're right there with you. Unreal Engine 5 games are notoriously heavy, and to some degree this is down to what the engine is doing. But it turns out that, at least partially, this is also down to the engine's crap optimization. We say that because CD Projekt Red's The Witcher 4 was the centerpiece of Epic's "State of Unreal 2025" presentation today, and it's running with all of Unreal's latest and greatest technology at a fairly consistent 60 FPS on a base PlayStation 5.
Make no mistake; it's clear that image quality has been sacrificed to get there. Not in terms of effects or materials, but in terms of resolution. The whole demo was presented with a visibly soft focus and a heavy layer of either motion blur, temporal upscaling, or more likely both. Still, it's impossible to deny that the demo looks incredible even at that, especially considering it's running at a full 60 FPS. Frankly, The Witcher 4 is hitting something very close to a cinematic CGI level of presentation thanks to the new features in Unreal Engine 5.6. Epic Games says that its Lumen ray-tracing tech runs "more than twice as fast" now as compared to when it initially launched.
In case you hadn't figured it out, The Witcher 4 centers around until-now-series-protagonist Geralt's adoptive daughter, Ciri. Early in the demo, CD Projekt's Sebastian Kalemba introduces Ciri's horse, Kelpie, which Epic Games' Wyeth Johnson uses in turn to introduce three features seeing major improvements: Multi-Character Motion Matching, Root Motion Movement, and the Chaos Flesh Solver. The former is a new method for matching up animations across two characters, while "Root Motion Movement" is an existing feature in Unreal Engine that allows characters to be moved in the game world by animation data, instead of by the game's movement systems. This allows for more natural and realistic motion, as there's no more danger of sliding feet when animation rate doesn't match the movement speed.
The Chaos Flesh Solver physically simulates the movement of muscles under skin.
The Chaos Flesh Solver is a component of the Chaos physics kernel that Unreal Engine uses, and as you could probably guess, it is intended for simulating the movement of flesh and muscle based on skeletal animation frameworks. It's highly realistic, and the demo of Kelpie's musculature working to propel the horse across the terrain is impressive, although in this Texas writer's opinion, the actual animations for the horse's motion could use some work.
Arguably the biggest feature that Epic announced today was Nanite for Foliage. Nanite is Unreal Engine's virtual geometry system that dynamically scales polygon counts based on screen resolution and object distance from the camera. Basically, if an object only occupies ten pixels on screen, there's no point in rendering out ten thousand polygons for it; the player literally can't see it.
Bringing this functionality to foliage is a huge deal, because it means that up close, every single leaf and pine needle can be individually modeled and rendered, but at a distance, clusters of leaves and needles are reduced to individual voxels. The end result looks great, and it can be affected by physics and lighting at a much lower computational cost. This reminds of how the chuky voxel game Teardown achieves real-time ray-traced global illumination at a smooth frame rate, even on integrated Vega graphics; the low resolution of the voxel geometry allows the renderer to take many shortcuts without visual compromise.
Another major update to the engine today was the announcement that MetaHuman Creator is now fully embedded within the engine, and has been revamped to allow the ability to create "a near infnite range of plausible body shapes." Epic Games' Johnson says that the refinements to MetaHuman were done to help ensure that the game in quality between Ciri and the game world's NPCs is as small as possible, and this is both about fidelity and about authenticity.
Finally, while he didn't provide many details, Johnson said that The Witcher 4 takes advantage of an "entirely new Unreal animation framework" that is radically more optimized than before. To show it off, the CD Projekt Red developers began adding characters to a marketplace scene, which, aside from some very brief loading stutters, remained running at a smooth 60 FPS even as the developers cranked up the actor count to "over 300".
While we're dubious that there are actually 300 visible ators in the scene, we admittedly didn't count them, and regardless of whether it's actually "over 300," what's visible is still an incredible number of characters standing around for a modern, current-generation game. If you did this in the current-gen version of The Witcher 3 it would barf with an out of memory error before you got halfway to this many visible NPCs.
