V Rising: Behind the vampire realm built on 1,600 ECS systems

Learn how Stunlock Studios made their monstrous open-world vampire survival adventure for PC and reached even more players by launching on PlayStation®5.

How do you make a multiplayer survival game on a massive scale? V Rising offers a sinister take on this popular genre, where players become vampires in a huge open world. Stunlock had big ambitions and scoped accordingly, implementing Unity’s Data-Oriented Technology Stack (DOTS) and High Definition Render Pipeline (HDRP) early in development to build a stable, scalable foundation for their most complex game yet.

With DOTS, Stunlock had the flexible code architecture they needed to effectively manage development on their increasingly large project, while HDRP unlocked high-fidelity visual effects like Volumetric Fog that were vital for establishing a Gothic atmosphere. With shrewd planning and the right tools in their arsenal, Stunlock launched V Rising on PC to rave reviews at early access and again at release, before further extending the game’s lifespan with a critically acclaimed PlayStation 5 port. The game has sold more than 5 million copies to date.

The results

• Created an expansive, server-based game world stretching over five square kilometers, with eight unique biomes
• Streamed and rendered more than 160,000 interactable objects in real-time
• Managed 21,000 baked prefabs, 450 baked subscenes, 1,600 ECS systems, and 2,700 particle systems
• Saved hundreds of hours using the Unity Profiler to quickly identify suboptimal code and unnecessary garbage creation
• Eliminated multiple ms of frame lag with the SRP Batcher
• Recorded high engagement metrics, with players spending an average of 35 hours in game and unlocking more than 3.4 million PlayStation™Network Trophies and Steam Achievements to date
• Implemented PlayStation 5-specific features including automated Voice Chat, support for the DualSense™ wireless controller's Haptic Feedback, Adaptive Triggers, and controller sound effects, plus a PlayStation™Network Trophy system

Scoping out the game world

For V Rising’s setting, the continent of Vardoran, Stunlock envisioned an interactive, persistent world with eight distinct biomes. Each would be shrouded in fog, featuring a day/night cycle with real-time lights and shadows, which would have to remain performant at runtime to deliver consistent online gameplay. “We decided to go all-in and implement it all in Unity with no restrictions, which has given us a lot of freedom to create the vampire realm of our dreams,” says studio cofounder and system programmer Fredrik Haraldsson.

Scaling up operations with DOTS

Stunlock had been closely following Unity’s recently announced DOTS, which presented solutions to many of the performance challenges they anticipated. Though the tech was still experimental, V Rising was early in development and Stunlock’s programmers already had experience with data-oriented design. Adopting the technology early would also give them the opportunity to partner more closely with Unity and get project support in exchange for battle-testing DOTS in production.

Excited by the potential this could unlock for V Rising, Stunlock’s devs started creating the technical framework for the project in Unity 2019.3, while the rest of the team continued prototyping using the in-house engine they’d previously used to build Battlerite to keep development flowing.

Slaying performance drainers

Building V Rising’s project architecture using DOTS and ECS took time, but the benefits soon became apparent. “With DOTS, we built a foundation that could handle much more content, and we could leverage streaming entities and assets effectively,” says Rasmus Höök, cofounder and technical director at Stunlock Studios. Subscenes and asset streaming are used to load and unload elements dynamically at runtime based on what the player can see in-game. This technique makes exploring V Rising’s massive world a much more performant experience for players.

Building V Rising with ECS also meant leveraging subscene baking to manage game content. Because entities are incompatible with Unity’s core scene system, they can’t be directly included in Unity scenes. Instead, baking allows entities to be loaded from scenes, converting their GameObject and MonoBehaviour components into entities and ECS components that can be loaded at runtime.

Rasmus argues that this clear separation of runtime data and Editor data is one of the biggest benefits of working with DOTS and entities. “Working in the Editor, we create authoring prefabs, which are essentially standard GameObjects with MonoBehaviors. However, these prefabs are solely for editing purposes and are not directly used in the game itself,” he explains. “Instead, they go through a process called baking where they are converted into runtime components. Since the authoring prefabs are only used in the Editor, it allows us to add functionality and data to them to improve the workflow without worrying about cluttering the actual game.”

Using authoring prefabs in this manner makes it easier to update V Rising. Rather than tweaking one element of a system and asking artists and designers to update thousands of related prefabs, Stunlock’s programmers can simply alter the baking code to pull data required by the updated system. “This helps with maintenance, but it obviously helps with performance as well,” says Rasmus. “Because on the prefab there can be Editor-only data, which isn’t converted to a runtime component – so you skip all that overhead.”

Overcoming roadblocks

As Stunlock anticipated, working with experimental technology comes with a few hurdles. “Many of the issues we had in the beginning were self-inflicted. A lot of the entities we created were too big, they have a lot of components, which means we can’t fit as many entities together as we’d like,” says Rasmus. “To solve this issue, we made them smaller and increased the chunk sizes, which made it much better. There’s only so much you can do when you’ve already made the game, other than learn from the experience.”

Because working with DOTS is a significant departure from previous Unity development paradigms and more complex, Stunlock onboarded the team gradually. Programmers were assigned small tasks writing simple components and authoring code to get accustomed to the new authoring process. Soon enough, they were using DOTS components like the C# Job System and building tools to speed up development and improve quality assurance across the team.

“Using the C# Job System, we have built tools that can scan meshes in the project for duplicate geometry, or calculate the polygon density of a mesh to identify assets that may need to reduce the amount of subpixel triangles,” explains technical artist Filippa Arvidsson.

“The data-oriented approach of DOTS is my new preferred way of working with code in Unity, as I find it very intuitive once you get over the initial bump of shifting your mindset from GameObjects to systems. And the performance benefits are also a big plus, of course.”

For less technical team members, Stunlock implemented workflows on top of the DOTS codebase to make contributing to the project more straightforward. One workflow enables the creation of prefab components that generate and listen for predefined events, like effects that occur when a player spawns, or buffs that are applied when certain conditions are met. Using this system, designers can create modular, manageable gameplay elements without deep technical knowledge of DOTS.

The second workflow, built primarily for feature implementation, has designers working in a scripting layer with a constrained API. This allows them to author their own scripts that can interact with components and register themselves to different events, speeding up production.

Unleashing graphics and gameplay with HDRP

V Rising is built in HDRP, which unlocked higher fidelity graphics capabilities that shaped the player experience in interesting ways.

“Volumetric Fog is absolutely the visual effect that influenced the game the most,” says Rasmus. “When our artists knew we were going to be using HDRP, they adapted the style around that, so HDRP influenced the overall look of the game.” In addition to creating atmosphere and adding visual flavor to spells and abilities, Volumetric Fog is used as a line-of-sight mechanic, masking areas the player can’t see.

Stunlock uses HDRP’s Physically Based Sky to manage V Rising’s day/night cycle, which comes with game mechanics that were crucial to get right. During daytime, the player takes damage if they linger in sunlight and must skulk in the shadows to move through the world. Safe and harmful zones had to be clearly defined so this mechanic wouldn’t become frustrating.

“Real-time rendering is very important, both to create beautiful transitions between different times of the day, but also to visually inform the player of where the sun will burn them,” says Filippa. “HDRP worked very well for this, allowing our artists to set up different volume profiles for different times of day for different areas, that we could smoothly blend between.”

Stunlock took full advantage of HDRP’s scriptability to build hundreds of custom visual effects, shaders, and post-processing passes. Filippa recalls one effect, built as a custom post-processing pass, that darkens objects close to the camera, which appears throughout the game and is used to set the mood in V Rising from the beginning.

“For example, in the starting crypt, there are these high pillars towering over the vampire. The post-processing pass makes them appear darker the closer they are to the camera,” she says. “It immediately establishes this very unsettling atmosphere, which adds a lot.”

Stunlock also customized HDRP’s source code to their needs, stripping away redundant features and calculations to improve performance. They extended volume profiles to drive components beyond typical HDRP effects. This enabled less technical game developers like artists and designers to easily configure elements like weather, music, and sound effects in different scenes independently in the Editor.

“It was really powerful to be able to expose this to the artists,” says Filippa. “This way, they could get each biome to look exactly how they wanted at each time of day, with minimal tech support. It definitely saved a lot of time.”

Seeking new blood on PlayStation 5

V Rising is Stunlock’s first console game, and when they were approached by Sony, they jumped on the opportunity to take on a new challenge and reach potentially millions more players on PlayStation 5.

Programmers began by upgrading Unity versions to take advantage of ECS 1.0’s additional performance improvements. The PC build’s main thread had been a limiting factor, so they used the C# Job System to distribute work to other threads. Safe scheduling helped them easily create jobs on the main thread that didn’t interfere with other tasks. “We did the majority of our development pre-Entities 1.0, and now, after having upgraded, we’re using journaling a lot to see what’s happening, which has also been very useful,” says Rasmus.

On the graphics side, Filippa noted that batching had a big impact on PlayStation 5 rendering performance, so they built tools in HDRP for a modified UDIM workflow that allows them to combine submeshes with different materials to reduce draw calls. “This likely saved us multiple ms worth on the CPU side, as rendering data could be sent to the GPU in a much more efficient way,” she says.

Taking over the night

Between the 1.0 release on PC, the PlayStation 5 launch, and a recent partnership with Konami Digital Entertainment (KONAMI)’s legendary Castlevania franchise, V Rising has been going from strength to strength. It's an exceptional technical achievement from a small team willing to boldly experiment with new technology to create captivating and unique experiences for players.

With DOTS, Stunlock could add “way more of everything” to V Rising with minimal performance issues, while HDRP helped them create haunting visual effects for a more immersive and engaging player experience. Today, V Rising is one of the biggest DOTS-based games on the market based on lines of code, and Unity is leveraging insights from the production to make the Editor even more performant and stable for creators building ambitious games.

“It wasn't our intention from the beginning to have this many dynamic and destructible elements – it was just something that happened because we could,” says Rasmus. “It’s a testament to how good ECS is, and the significant performance benefits it can achieve. Without DOTS, the V Rising we have today would have been very different.”

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