Courtesy of Croteam

Inside Croteam's transition from in-house tech to UE5 for The Talos Principle 2

Brian Crecente
Davor Hunski is the Chief Creative Officer at Croteam, a leading game development studio based in Croatia. He is considered the grandfather of Croatian game development and has worked in the industry for over three decades. Hunski’s notable contributions include being the main game designer and production manager for games such as Serious Sam and The Talos Principle. Davor Hunski takes great pleasure in collaborating with a team of exceptionally talented up-and-coming game development stars at Croteam.
Goran Adrinek is the lead programmer at Croteam, a famous Croatian game development studio where he started his game development career more than 16 years ago. Raised on Croteam’s own Serious Engine, Adrinek started as a gameplay programmer, but soon became a jack of all trades, dealing with low-level engine systems, editor and pipeline tools, networking, scripting, and navigation—to name a few of the areas of his expertise. For the last couple of years, he’s been leading Croteam’s switch to Unreal Engine.
Croatian developers Croteam have been creating over-the-top Serious Sam first-person shooters for more than two decades and they’ve been building them on their in-house engine for just as long.

But the team said they came to a realization following the release of Serious Sam 4 in 2020: It was time to retire their Serious Engine and shift all future development to Unreal Engine.

Distinctly not a shooter, The Talos Principle 2 will be the first game the team releases that is built on Unreal Engine.

We chatted with Croteam’s Chief Creative Officer Davor Hunski and Croteam lead programmer Goran Adrinek about the reasoning behind the engine shift, why the team will unlikely ever return to their own tech, and some of the inspiration behind puzzle game The Talos Principle 2 and its deep philosophical roots.

What made Croteam decide to create a puzzle video game after spending more than a dozen years working on the first-person shooter franchise Serious Sam?

Davor Hunski, Chief Creative Officer, Croteam:
It may not be widely known, but our journey in game development began with a puzzle game, and our first published venture was a soccer game. As the early ’90s rolled in, we were captivated by the world of first-person shooters. This fascination culminated in the birth of Serious Sam. However, our interests extend far beyond the realm of gaming.

When we convene around a table, our conversations span culture, philosophy, religion, technology, AI, and the future. The creation of The Talos Principle provided us with the ideal canvas to reveal other facets of our personalities and articulate some of our perspectives on the world.
Courtesy of Croteam
Why did the team decide to inject such strong elements of philosophy and transhumanism into The Talos Principle?

Themes of this nature never cease to captivate our imaginations. Countless times, we’ve delved into profound discussions about humanity’s place in the vast tapestry of time and space. The juxtaposition of human civilization on one side and the enigmatic—maybe even dangerous—future on the other has consistently left us awestruck during these conversations. It became imperative for us to share our perspective on this captivating subject with the world.

What challenges did the team face when trying to create a sequel for a game with such a tight ending?

Truth be told, we encountered numerous challenges along the way. We were aware of the monumental undertaking before us from the very start. Contemplating the creation of a sequel to such a magnificent work of art was a daunting prospect. Initially, it wasn’t even on our radar. However, over the span of five years, something remarkable happened—a gradual, organic emergence of creative sparks and ideas. Piece by piece, they wove together the tapestry of our vision: the story, core game mechanics, environments, and more. This ever-expanding repository of concepts became the foundation upon which we assembled the mosaic we now proudly call The Talos Principle 2.

Why did the team decide to create The Talos Principle 2?

The journey to reach the confidence required to envision a game deserving to follow in the footsteps of our beloved The Talos Principle was lengthy. Crafting a sequel after the immense success of its predecessor is undoubtedly challenging, yet the potential we saw in The Talos Principle 2 was simply too compelling to resist. Now that we’ve brought it to life, we find ourselves experiencing that unmistakable, exhilarating sensation once more, akin to a parent’s joyful anticipation as they await the birth of their precious child into this beautiful world.
Courtesy of Croteam
Croteam has been using and updating its Serious Engine for nearly 25 years. What made the team decide to build The Talos Principle 2 in Unreal Engine 5?

Goran Adrinek, Lead Programmer, Croteam:
When we released Serious Sam 4, we recognized the need to elevate our engine and rendering capabilities for our next project. We compiled a list of enhancements and calculated the time and financial investment required to implement them, and the outcome was disappointing. We found ourselves struggling to reach the level of quality even Unreal Engine 4 had already offered at that point. We witnessed the dazzling Unreal Engine 5 demo shortly after, showcasing the groundbreaking Nanite and Lumen technologies. It became evident that this marked the final chapter of Serious Engine development.

Croteam’s primary aspiration has always been to craft enjoyable games. While we have a passion for engine development and associated technologies, our main objective has consistently been creating exceptional gaming experiences. Unreal Engine was there waiting for us, all shiny and proud, with its sparkling promise, urging us to embrace it. Once we put it to the test, there was no looking back.

What sort of challenges did the team face in transitioning from the Serious Engine to Unreal Engine 5?

Adapting to an entirely different engine was a process that demanded both time and effort. We knew it was crucial for our programmers and content developers to feel at home in this new environment. While it took some time to achieve that comfort level, we always understood that this investment will pay off.

At the start of the project, we began working with Unreal Engine 4, eagerly embracing each new engine iteration as it was released. Initially, we planned to use a rendering path of prebaked lighting, and we were struggling with this approach due to the size of the levels. However, as our journey unfolded, we fully embraced the almost magical capabilities of Unreal Engine 5 (starting with 5.0 and moving with each iteration until release on 5.2). To accomplish this, we drew upon the programming expertise cultivated through our Serious Engine experience.

Ultimately, the biggest challenge was finding all the systems to make a complete game in a new, unfamiliar engine—something like learning to play a new instrument for a musician who is a virtuoso in another instrument. But slowly and surely, we are reaching that virtuoso level in Unreal Engine.
Courtesy of Croteam
Are there plans to continue to support Serious Engine or is this a permanent shift to Unreal Engine 5? If the latter, why?

This is a permanent transition to Unreal Engine, as we recognized the almost impossible task of bringing Serious Engine up to the quality of Unreal Engine. It would be like attempting to sprint and catch up with a train that is already far down the track and accelerating even faster. Unreal Engine has proven to be an outstanding platform that seamlessly accommodates all our game development requirements.

Were there any particular features of UE5 that helped you realize your vision for the game?

We fully embraced the latest and most cutting-edge features of UE5, such as Nanite, Lumen, World Partition, Virtual Texturing, Virtual Shadow Maps, and Local Exposure. These technologies have long been considered the holy grail of game development since the industry’s early days. The countless hours and effort previously dedicated to creating LODs or shadow maps are now things of the past, freeing up valuable resources and time that can be used to enhance other aspects of the game.

The lighting in The Talos Principle 2 is amazing. How did you make use of Lumen in the game’s rendition of light and water?

With nearly three decades of game development experience under my belt, spanning 2D to 3D to virtual reality, I can confidently claim that the introduction of Unreal Engine 5 represents a game development revolution like few others I’ve witnessed. Lumen, in particular, is nothing short of astounding. While it demands some effort and comes at the cost of a fraction of your frame rate, the results are breathtaking. Every scene in the game reaps the benefits. What’s even more remarkable is that we’re fully aware we’ve only scratched the surface of its potential. Truly, it’s nothing short of amazing!

The world of The Talos Principle 2 looks massive. How did Nanite help you achieve the look and scale of the game?

Utilizing the old rendering methods would not meet the requirements for the game to run at a decent frame rate. Fortunately, the seamless integration of Nanite into our content production pipeline made the transition to this innovative rendering path and workflow relatively smooth. More recently, our adoption of world partitioning technology has played a crucial role in breathing life into our expansive levels.

Did using Unreal Engine 5 have an impact on the depth or sort of puzzles you could include in the game? If so, how?

While it didn’t significantly impact the development of our puzzle logic, World Partition was crucial for creating vast environments and forming the new core structure for the game without the constant concern of needing additional space or new locations. Also, it allowed us to completely forget about the limit of only one developer working on one level at a time. Additionally, it enabled us to craft the immense spaces that players will encounter later in the game. What truly stands out about UE5 is its ability to empower developers to concentrate on the game itself rather than grappling with the constraints of technology.

How do you think the game’s mechanics and philosophy has evolved since the original Talos Principle?

While The Talos Principle was, in a sense, a focused and even considered minimalistic game, The Talos Principle 2 dwarfs its predecessor in numerous ways. It has expanded both in scale and scope, having more environments, game mechanics, space, story, and systems—essentially, more of everything. Even though the learning curve in The Talos Principle was much praised, we decided to take a daring leap by introducing a slightly different game structure. It was a bold move, but we believe it was well worth the risk.

As for the narrative, we were determined not to replicate the same formula, delving introspectively once more. Instead, we embraced another risk, introducing a vibrant society of captivating characters and further evolving the storyline to capture the cherished essence of early science fiction novels.
Courtesy of Croteam
Is there room left in The Talos Principle for future titles, or is this prologue the end of the franchise?

We internally know the answer to this question.

How do you believe work on The Talos Principle games impacts what you bring to other titles, particularly future shooters, like the next Serious Sam?

Of course, we learned so much. We’ve assimilated into the Unreal environment, accumulated knowledge, and reached impressive development velocity. Our team of developers is nothing short of extraordinary, with each Croteam member being an exceptional professional and a beautiful spirit. Collaborating with them to craft art of this caliber is just priceless. The development of The Talos Principle 2 has been a time of tremendous growth and learning for us all, igniting our excitement to embark on our next project.

Thanks for taking the time to chat with us. Where can people find out more about The Talos Principle 2 and Croteam?

More on Talos 2 is available on our website. Thank you for chatting with us.

    Get Unreal Engine today!

    Get the world’s most open and advanced creation tool.
    With every feature and full source code access included, Unreal Engine comes fully loaded out of the box.