The Witcher 4 tech demo interview: "we're building a world that will be very rich and very, very interactive"

This week CD Projekt Red teased its next project, The Witcher 4, with a tech demo in Unreal Engine 5, showing off some of the technology powering the Polish company’s open-world RPG. Although not from the game itself, the short showcase gives a sense of the massive ambition driving the developers, who want to trigger the next generation of role-playing games. 

The demo shows off a massive world where thousands of trees can be rendered into the distance, forests packed full of foliage, powered by Nanite, allowing them to sell the illusion of that density even from vast distances away, without sacrificing performance. 

The team also showed off multi-character motion matching and realistic horse muscle deformation, a more natural animation method to ensure that Ciri and her horse move together as you ride through the mountains in Kovir. 

Later, the demo takes us to a marketplace filled with NPCs with dozens of routines. People chat, argue, and react to Ciri as she passes through. Sellers hawk their wares and children clap as a man urges a tamed bear to perform tricks to the crowd. Shortly after, Ciri bumps into a passing villager and knocks the crate of apples from their hands. Each apple rolls independently down the slope and a child runs up to grab one, followed by a pair of pigs who were previously wallowing in mud. 

All of this was played on stage live on a base PS5 at 60fps and with ray traced global illumination. 

But how much of what we saw will actually be in The Witcher 4? I sat down with engineering director Przemysław Czatrowski to find out. 

Read More: The making of The Last Wish in The Witcher 3

DBLTAP: Obviously what we saw was a tech demo, but is it indicative of what you hope to achieve with the game?

Czatrowski: This is definitely the direction that we want to go. The demo we presented is basically showcasing the technology that we use for building the game. So we're just super proud and super happy to share the toys that we have to build the entire thing. And yeah, the demo is basically [a showcase of the] visuals and the overall direction that we want to go, but it doesn't represent the game itself. 

DBLTAP: Yeah, the wording was, this is set in the world of The Witcher 4, right? So does that mean the environments in the demo are in the game? 

Czatrowski: So, with this demo we are showcasing Kovir, which is the area in The Witcher universe that we'll be exploring in the game. So this is the expectation. Expect vast, open spaces, mountains, snowy areas and so on, with lots of foliage, monsters roaming around. 

DBLTAP: Yeah, I noticed there was a bear crossing a creek, and that's one of the things The Witcher 3 was missing – the ecosystem. Because it's about hunting monsters, but animals live within that ecosystem too, right? Are you hoping to include an ecosystem of AI agents that aren't humans?

Czatrowski: We are very much focused on building a world that will be very rich and very, very interactive. So in order to captivate the player, there are some elements here and there that we just put to show how ambitious we want to go with it, and how rich and interactive. 

DBLTAP: There's also a bit where Ciri goes to the quest giver, she leans over the balcony, and it reminded me of how you framed scenes in Cyberpunk. It's that technique used in Cyberpunk, where you lean on something and then you've got a really interesting backdrop while the conversation goes on. Is that stuff that you managed to salvage from Cyberpunk and bring into the Unreal Engine?

Czatrowski: We have a really strong collaboration with Epic, and a really great one in terms of the tech that we are pushing forward. So this is a result of this collaboration, because we know what we want to achieve. Epic engineers and developers are really helping us to get where we are and to get where we want to be, technically speaking and also, working day to day with them, we learn a lot about the engine. But at the same time, we're not rookies, so we have stuff on our own that gets into the engine later on. 

DBLTAP: What about the stuff that you developed specifically for Red Engine? Because there was obviously years and years of pre production for Cyberpunk, and you made all this new tech for this open world. There must be some of that stuff you're bringing into Unreal Engine, right?

Czatrowski: I think what we bring is ideas and ambitions, because those are the ones that can be implemented everywhere. The idea is the secret sauce that we can bring everywhere, and it will hopefully work out for the best. 

DBLTAP: So that scene where she leans over – is that a hint that you might frame conversations in a similar way to Cyberpunk, where they're a bit more dynamic than they were in The Witcher, where it's more talking heads?

Czatrowski: There are a couple of elements in the demo that we showcase, because it made so much sense for the story in the technical demo. However, this tech is still in development, and it's too early to say, like, is it going to be this way or that way, or something new. So we are trying out some things. We see what works, what doesn't work, and we adjust along the way.

DLBTAP: In the presentation, you put a lot of emphasis on how responsive and emergent the world is. Is that something that you're working with Epic on to achieve?

Czatrowski: Yeah, definitely. So, like, you spotted the bear already. This is one of the elements, maybe more in the background. However, in the foreground, you saw the scene where Ciri bumps into the guy carrying the crate of apples and apples basically just like, roll down and send this signal for other NPCs, animals and so on. So these are the chain reactions that we wanted to showcase. This is what we are aiming for – this interactivity, not only between the player and the world, but also interactivity between the elements in the world. 

DBLTAP: You couldn't really interact with the NPCs in The Witcher 3. You could interact with the main ones and have conversations with them, but beyond conversations, you couldn't really disrupt their routines or anything like that. Are you working towards making the world this dynamic across the board?

Czatrowski: We want it to be as interactive and as dynamic as possible. We have some examples already that we showcased in the demo. However, the full scope is still work in progress, so we'll see how far we'll get. 

DBLTAP: Yeah, I understand why you're being a little cagey about it is because obviously, if that's going to work, you're going to need 50 or 60 different examples of that, right? Because otherwise it's gonna just repeat. You can’t just have Ciri bumping into apple crates all the time. 

Czatrowski: At the same time, if you're able to make it systemic, things will be much easier.

DBLTAP: Yeah, I mean, Red Dead Redemption 2 managed it. There's a lot of unique interactions across the world in that. So I think it's possible.

Czatrowski: It's a great game. All the studio, all the desks, played it and loved it. We don't draw direct references or comparisons from it, but definitely, we love the vibe. 

DBLTAP: Obviously this is a short tech presentation, but do you think it's possible? I know you, you're not there yet, and it's only a tech demo. But do you think it's possible to do everything that you’ve shown there in a full open world game?

Czatrowski: So, this is the showcase of the current state of the engine. Basically, 5.6 is out, and lots of the stuff that we showcased is already available for the devs. And so, yeah, basically, this is it. With the tools that we are using in the studio, you are able to start building this open world experience.

DBLTAP: So when the guy was on the stage with a controller in his hand, was he really playing that?

Czatrowski: Yes. It was a 100% live presentation being played on a base PS5. 

DBLTAP: And is it one of those demos where, like, if he looked the wrong way, it would have broken? How scripted was it?

Czatrowski: No. I mean, if you look the wrong way, you can possibly see a part of the map that was not developed because it's a short fragment of the world that we built specifically for them. Also, if you look the other direction, there might be some more empty space. But at the same time, if you look the right way, you can see all the technology that we showcase – basically infinite forest, foliage reaching up to the horizon. You could see the NPCs on the market. You can see the interactivity and systemic approach for those interactions. You can see the horse, which is beautiful, powered by machine learning technology, and you can see the beauty of the world.

DBLTAP: When you did the zoom in for the horse muscles, did you just create a short cutscene to showcase that? How did that work? 

Czatrowski: Parts of the demo were designed in order to showcase more technology, but it was still running fully on the PS5. None of the parts that were shown were pre recorded. 

DBLTAP: You might answer this because you didn't show it, but what does Unreal Engine mean for your night, day, weather systems?

Czatrowski: Of course, it's a very important part of open world [games]. However, we didn't showcase it because it's still in the works for us. We're still figuring out what we can do with it, and how it can enrich the final product.

DBLTAP: What implementation of ray tracing was in the demo?

Czatrowski: We have 60fps with hardware ray tracing. We have ray traced global illumination.

DBLTAP: The muscle deformation tech that we mentioned before. Is that limited to just horses, or is that every creature, every human in the game? 

Czatrowski: This is basically a technology that allows you to build the model, to simulate the muscles and transform it to the final to the final mesh. The limit is your imagination.

DBLTAP: So you'd like to have it for everything?

Czatrowski: It's way too early to say. We just showcased it on the horse, and it's a great example of it. However, for the rest we are still evaluating. 

DBLTAP: Can you talk to me about the physics and cloth simulation? Because I noticed Ciri’s rocking that long cape to show that off. 

Czatrowski: Physics simulation is tricky. It's especially tricky with all the collisions that you have to resolve. First of all, we have the cape that moves really naturally when Ciri is walking. But at the same time, if you, if you watch the recording, you could see Ciri mounting the horse, and then the cape also works really believably. This is a great example of this technology being pushed forward and still being able to fit into the 60fps budget.

DBLTAP: And I guess that applies to the apples, too, because if you'd bumped into them in a slightly different place they would have rolled differently. That’s not a canned animation, is it? 

Czatrowski: No, those apples are rolling on physics, yeah.

DBLTAP: Is there anything that people haven't spoken much about that was in the tech demo that maybe you'd like to highlight?

Czatrowski: There are a couple of highlights. Personally, being in tech for quite a few years now, the entire demo is very heartwarming, because it shows how powerful the implementation and optimization can be. Because we were showing it on a base PS5, with hardware ray tracing and 60 FPS, and still achieve this visual fidelity – I think no one could guess that this is possible at this point in time. So for me, the entire demo is a gem to watch over and over again. 

DBLTAP: When you say base PS5, is it an actual base PS5, or is it a PC that's got the same specs as a base PS5?

Czatrowski: No, this is a PS5. This was a PS5 plugged into a huge screen with a real controller and a real person playing the game. 

DBLTAP: How long did it take to make that demo?

Czatrowski: I think the project started roughly a year ago.

DBLTAP: How many people worked on it? 

[PR person cuts in] No, we're not getting into detail today. It was a dedicated team, a very hard working team. 

More: The making of Open Sesame! in The Witcher 3