Exploring the post-apocalyptic charm of ASG open worlds in Wuthering Waves

May 21, 2024
Kuro Games is a technology and internet company committed to developing high-quality content-driven games and producing original content. We take pride in our independent development of three remarkable products: Twin Tail Battleground, Punishing: Gray Raven, and Wuthering Waves.
Solon Li is Kuro Games’ CEO & Producer who has been dedicated to game design and operation for more than 10 years. Supervising the production of Kuro Games' Open-world Action RPG Wuthering Waves, Li has been the driving force behind every stage of development. Building on the commercial triumph of the previous game title Punishing: Gray Raven, he demonstrates exceptional knowledge as a versatile game creator for his deep expertise in anime action game design and operation.
Open-world games evoke images of a world filled with fantasy adventures, where the thrill of exploring vast landscapes merges with the excitement of engaging combat. Players navigate these realms, utilizing a variety of skills and weapons to confront diverse enemies, embark on quests, and face the challenges set by destiny, transforming the game's world in the process.

The allure of venturing into the unknown, combined with the craving for compelling narratives and dynamic, action-packed combat sequences, makes ASG (Anime-Style Games) open-world games extremely popular among players. These games offer a rich and enjoyable experience, whether through adventure, combat, social interaction, or immersing oneself in stunning environments.

Despite the genre's success and its contribution to some of the market's most iconic titles, it remains fascinating to speculate about the future landmark games that may emerge.

On Feb. 19, Kuro Games introduced the second closed beta for its ASG open-world game, Wuthering Waves. Developed with Unreal Engine, this cross-platform title for PC and mobile boasts a unique post-apocalyptic theme, fluid combat mechanics, and expansive open-world gameplay. We had the opportunity to speak with Solon Li, Kuro Games CEO and Producer about the game.
Courtesy of Kuro Games
Could you first tell us about Wuthering Waves and the team behind it?

Solon Li, Kuro Games CEO and Producer:
Wuthering Waves is an open-world action game that emphasizes freedom in action-centric combat and extensive exploration. In this game, players take on the role of an awakened Rover, embarking on a journey to recover their memory and identity while forming alliances to tackle formidable foes. The game allows players the freedom to explore and interact with its environment at their own pace.
As for the development team, it's composed of over 500 professionals, including contributors from mobile action role-playing game Punishing: Gray Raven, along with other skilled talents from across the globe. Our collective aim is to enhance the gaming experience for our players.

What unique artistic style does Wuthering Waves aim to present in the ASG game market?

Li:
With Wuthering Waves, we aim to showcase a richly developed civilization, emphasizing a sharp contrast in scenes and the use of complementary colors. For character portrayal, we're leveraging advanced animation cinematography techniques. We prefer using color grading strategies that create a strong filter effect, setting us apart from the typical flat animation style.

Which UE version is Wuthering Waves developed with, and why was this particular version chosen?

Li:
We chose UE4.26 for its stability and maturity when we started development. Throughout the development process, we integrated essential functions by incorporating new features from UE5 into UE4.26. This approach allowed us to meet our specific needs and maintain a steady flow of content production.

What are the main considerations when integrating 2D cartoon characters into a 3D environment?

Li:
Two critical factors are the time of day (TOD) and post-processing lighting.

The implementation of the underlying lighting system, especially TOD, is crucial in ASG projects. We utilized Unreal Engine's curve tools to simulate the natural daily changes in character brightness, ensuring they align with the 3D environment's lighting. This helps maintain accuracy in character portrayal within the open world and ensures visual consistency across the performance pipeline.

Additionally, we took a measured approach to the engine's physical features to achieve the "hand-drawn" feel. For example, we used limited sampling for certain elements.

Regarding post-processing lighting, we set up an independent character lighting pipeline. This allows for quick environmental lighting adjustments using presets and automated tools, now an integral part of our character and skill design workflows.

Why was deferred shading chosen for Wuthering Waves when so many mobile games opt for forward shading?

Li:
Our goal is to deliver top-notch visual quality on mobile devices. To achieve this, we utilized techniques like Screen Space Reflections (SSR) and Ground Truth Ambient Occlusion (GTAO). These advanced techniques rely on deferred rendering to boost rendering efficiency and streamline the pipeline.

For an open-world game like Wuthering Waves, where new content is continuously added, rendering technology faces significant challenges. Traditional Forward Rendering can lead to a rapid increase in shader variants, which raises maintenance costs. Deferred Rendering, however, offers advantages in managing materials, weather, day/light changes, and atmospheric transitions. It simplifies the pipeline's complexity and reduces maintenance costs.

Moreover, aiming for consistency in multi-platform development helps lower development costs. Deferred Rendering standardizes the development process, improving the efficiency of feature implementation and problem-solving. This uniformity enhances overall development productivity and reduces the workload for the art team when adapting to the mobile version.

Furthermore, advancements in mobile hardware have enabled the use of one-pass deferred technology. This method significantly cuts down the read/write bandwidth to 1.5G per second while maintaining a steady 60 frames per second rate, mitigating the issues of overheating and high power consumption associated with high bandwidth. This creates a strong technical foundation for optimizing performance in mobile applications.

After adopting the deferred shading pipeline, what technical challenges were encountered, and how were they resolved?

Li:
Implementing the one-pass deferred approach revealed limitations on specific platforms. For example, on the Mali platform, using PLS for one pass deferred is restricted to a 128-bit on-chip cache without alpha blend, only allows resolving one render target, and incurs extra performance overhead due to depth fetch. To address these challenges, we adjusted our effects implementation.

Moreover, we had to integrate rendering effects like SSR and GTAO without disrupting the one-pass deferred workflow. This required leveraging depth and scene color data from the previous frame to generate SSR, using re-projection for reflection mapping in the current frame, and improving SSR quality with denoising techniques.

Our testing showed that most mobile devices could support SSR at medium quality and GTAO at high settings without substantial performance loss.

How did you approach the design of the characters' features and personalities to ensure strong recognition and appeal? (For instance, Lingyang's integration of Lingnan lion dance culture in China.)

Li:
In the initial stage of art design, we focused on identifying a unique characteristic that could be highlighted throughout the production process. For Lingyang, our goal was to integrate the unique charm of lion dance culture into the Wuthering Waves world. We combined lion dance gestures with Hongquan martial arts to design his movements, creating a character with a dynamic and vivid presence.
Courtesy of Kuro Games
The game's high-quality cartoon rendering and detailed cutscenes created a terrific anime style. How is the style replicated in real time?

Li:
Our primary focus is on gradients. This involves a close collaboration between the engine and the production team. We have advanced the use of gradients in characters' base colors and mask textures, significantly evolving from our first closed beta I last year. For example, the character gradients on the system interface are meticulously crafted by our character production team.
Courtesy of Kuro Games
In UE4, we use the engine's lighting capabilities, fake volume fog, and post-materials to achieve the desired gradient effect. Additionally, custom color grading (LUT) is employed, and each scene is designed with stable underlying lighting. This ensures a consistent lighting baseline, allowing the graphics to directly engage players' emotions during their exploration and narrative experiences. Below is an extreme test sample for color calibration that we conducted in our preliminary research.
Courtesy of Kuro Games
For another example, the character PV for Danjin was rendered using the game's internal lighting workflow. Our lighting artists have precise control over the light and shadow dynamics through our custom lighting components.
Courtesy of Kuro Games
We also cater to the visual direction needs of our performance team, striving to keyframe as much as possible. Leveraging UE4's powerful Sequencer system, we have made enhancements to include as many visual elements as possible for detailed control.

For example, during the activation effect of marks in characters' ultimates, the shake intensity and frequency can be finely adjusted to align with camera requirements.
Courtesy of Kuro Games
What challenges did you encounter in portraying character movements and expressions?

Li:
In the early to mid phases of development, we relied solely on skeletal techniques for character expressions. This approach, however, presented the first challenge: it was difficult to quickly and accurately replicate many authentic animation expressions. As a solution, we shifted to a blendshape-based approach. We collected and categorized a wide range of expressions, creating a comprehensive library that accelerated production with the DCC toolchain.
Courtesy of Kuro Games
Another challenge was rendering detailed facial expression shadows. The intricate lighting required for performances exceeded what conventional facial shadow solutions could provide. To overcome this, we enhanced the facial lighting setup, enabling us to create specialized shadow effects that matched the specific needs of the performance, such as achieving vertical or emotional light source expressions. For example, the distinct top light effect in Aalto's character PV was possible only with special shadow textures.
Courtesy of Kuro Games
The third challenge we faced involved character rigging adjustments, particularly in complex and dynamic areas like joints. We turned to RBF technology to model these parts accurately, and we quickly validated and implemented the technology in our production process.

The integration of the Echo system with the characters' ultimates has greatly enriched the combat experience. Could you elaborate on the design and implementation of its visual effects?

Li:
It's not just about the Echo system and character ultimates. We unified the visual presentation of the entire combat loop.

As many know, the concept of Echoes was inspired by the gourd, a traditional Chinese motif. In terms of visual effects design, we maintained an effect where the echo is absorbed in a spiral pattern, reflecting this cultural element.
Courtesy of Kuro Games
For the presentation of Echo abilities, we utilized a unified material controller and the Niagara effects system, integrating them within the combat loop. To maintain visual consistency, the effects of Echoes—whether being crushed, dropped, absorbed, or awakened—are rendered in a golden hue. This enhances the sensation of the curves in dissolution and other material aspects.
Courtesy of Kuro Games
The environment design in the game merges modern, sci-fi, and traditional Chinese architectural elements, creating distinctive areas like Lightless Forest. What inspired these designs, and how do they serve beyond aesthetic appeal?

Li:
Our inspiration was to depict a post-apocalyptic world in the midst of reconstruction, where remnants of both ancient and contemporary civilizations blend together. Players will come across modern relics like abandoned cars and village ruins affected by the Tacet field, which hint at the historical context of these settings.
Courtesy of Kuro Games
In developing the wilderness map, our goal was to create an environment where players feel their actions can significantly impact the world. To that end, we designed various themed maps that visually reward players as they complete tasks.
Courtesy of Kuro Games
How is the weather system implemented in Wuthering Waves, and does it include any unique elements beyond the standard day/night and weather changes?

Li:
We chose to develop a stylized day/night lighting system rather than using Unreal Engine 4's physical atmosphere system to better match our game's artistic style. Our system allows for real-time, accurate sky color adjustments without the need for pre-computation.
Courtesy of Kuro Games
To align the sky more closely with the game's conceptual design, we moved away from volumetric clouds, opting instead for a more streamlined 2D to 3D skybox rendering process. This method enabled us to create diverse sky appearances enriched with colors and depth that change with the time of day (TOD).
Courtesy of Kuro Games
To address the absence of real-time volumetric clouds, we included animations of clouds forming and dispersing to add dynamic cloud movements.
Courtesy of Kuro Games
Additionally, we introduced a unique weather condition called Retroact Rain, where the sky takes on the appearance of an inverted ocean. We developed a complete set of Etheric Sea and Retroact Rain effects based on the weather system to facilitate these special weather changes.
Courtesy of Kuro Games
Entering the Tacet field, players will notice the sky becomes muted with stationary clouds, and activating the central cords will cause the Etheric Sea to accumulate gradually. These visual elements are not only part of the game's natural environment but also play a role in performances, where we can manipulate the suspension of raindrops within a scene.

This weather system has been integrated throughout the game's open world, combat, performance, and mission pipelines for various development teams. It provides a consistent visual framework and minimizes redundant work on visual effects.

Going forward, we plan to continuously enhance the game's visual appeal with each update, showcasing the artistic talents of our team and expanding the depiction of Wuthering Waves' unique atmospheric phenomena.

How did you manage to render a large number of trees on mobile, similar to the PC version, without compromising performance?

Li:
To achieve this, we employed platform-specific categorization and optimization strategies. On PC and consoles, we use actual 3D model trees for the foreground, billboards for the mid-ground, and imposters for the background. For mobile platforms, we optimize further by using billboards for the foreground and imposters for both the mid-ground and background.

Billboards play a crucial role in our optimization process. They essentially replace the original 3D model trees with multi-layered tree leaves that always face the camera, significantly reducing the polygon count—typically to about 30% to 40% of that of model trees—while still achieving a similar visual effect.

However, using billboards comes with its own challenges, particularly regarding shadows. Since billboards face the camera, their shadows can rotate with the camera movement, which can be problematic for the realism of the scene. To address this, we adjusted the billboards to face the light source during shadow rendering, which effectively resolved the issue.
Courtesy of Kuro Games
For the imposters, we implemented a dynamic loading and unloading system that manages the imposter slices efficiently. This system, combined with a dynamic Texture Array, allows for the batch rendering of distant trees and ensures high efficiency in rendering.

Could you elaborate on the design and technical implementation of the mini-games, like 2D side-scrolling platformers and puzzles, within the main gameplay of Wuthering Waves?

Li:
Our aim was to enrich the game world and maintain a fresh and engaging gameplay experience. The side-scrolling format, in particular, was chosen to enhance the parkour elements within the game.

From a technical standpoint, significant customization was required, particularly concerning camera positions, character control, and scene setup.

For the camera, we redesigned the camera position and implemented new following mechanics. Regarding character control, we made adjustments to fit the side-scrolling dynamics. In a 3D environment, characters exhibit angular velocity when turning, which can lead to control lag in a 2D side-scrolling context. To counteract this, we increased the characters' turning angles.

For scene design, the transition from 3D to 2D imposed certain constraints, such as a predefined player path and limited camera movement. This necessitated a tailored approach to scene creation.

If there's an opportunity to upgrade to UE5 for Wuthering Waves, what aspects of the game would you focus on enhancing or improving?

Li:
One primary area we'd focus on is integrating Lumen. In an open-world game like Wuthering Waves, with its varied terrains and dynamic weather and lighting conditions, baked lighting often falls short. A dynamic GI solution would allow us to render more realistic environments, significantly enhancing player immersion. Lumen's excellent GI capabilities and user-friendliness make it an attractive option for us.

Another area we'd look into is upgrading the Niagara system, including GPU particle baking. The current limitations of mobile hardware, such as computation speed, power consumption, and compatibility, restrict our ability to support large-scale, visually impressive particle effects. With Niagara's enhanced performance and functionality in UE5, we could provide a more engaging combat experience.

Lastly, we would focus on improvements in multi-threading across game, render, and RHI processes. For a fast-paced action game like Wuthering Waves, maintaining a smooth frame rate is crucial. Optimizing multi-threading would further improve the frame rate, ensuring smoother visuals and gameplay.

Could you share some insights and experiences on developing high-quality ASG games?

Li:
Developing high-quality ASG games requires a strong focus on the game concept and IP settings. The artwork needs to be cohesive and to achieve this; we establish various evaluation processes during implementation. These processes help us continuously refine and improve the overall visual effect to ensure it meets player expectations.

Another crucial aspect is the gaming experience across different platforms. We strive to guarantee a solid base experience on mobile, with identical graphic details, gameplay, and other elements. We pay close attention to player feedback on mobile platforms, particularly focusing on their comfort during gameplay. This insight was a key takeaway from the initial technical test of Wuthering Waves.

For the PC version, we incorporate advanced features. As you can see in our previous test, we optimized texture density, mesh density, and even the design itself. This allows us to achieve detailed visuals on 2K displays while maintaining high recognizability on mobile devices.

Thank you for your time. Where can everyone go to learn more?

Li:
Thank you for having us! Please visit the game's official website and YouTube channel for all of the latest updates. You can also find Wuthering Waves on the Epic Games Store here.

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