Image courtesy of Netmarble

Ni no Kuni: Cross Worlds pushes the boundaries of what a mobile MMORPG can be

Jimmy Thang |
July 6, 2022

The world’s biggest online game publisher, Netmarble has banded together with top development studios to become a global gaming force to be reckoned with.
Developed by Netmarble in collaboration with Level-5, Ni no Kuni: Cross Worlds is an MMORPG that pushes the boundaries of mobile gaming. With cutting-edge graphics based on artwork by beloved animation company Studio Ghibli, it features fantastic character work and diverse environments with numerous biomes, all topped off with superb animation befitting a top-notch anime.  

To see how the team pulled off these incredible feats, we reached out to Netmarble to delve into how various Unreal Engine tools like Sequencer, Animation Blueprints, Material Editor, Live Coding, and more were instrumental to the game’s development. The team also shares how they wanted to design a story-driven MMORPG experience and delve into how they implemented the game’s smooth net code.
 

For those unfamiliar with the game, what can you tell us about Ni no Kuni: Cross Worlds?
 
Creative Director Yong Tack Oh:
Ni no Kuni: Cross Worlds is based on a game series called Ni no Kuni made in collaboration by Level-5 and Studio Ghibli. This game is an MMORPG where numerous players can venture into the fantastical and beautiful world of Ni no Kuni. Not only that, they can create unforgettable experiences inside and outside the game.

Did the team have any influences coming into the project?
 
Oh:
Almost everyone working in the entertainment industry recognizes Studio Ghibli for their spectacular animated films. It's a great honor for us, as game developers, to be able to make a game based on Studio Ghibli's legacy. On top of that, our active cooperation with Level-5 while working on the project has touched our hearts.
Image courtesy of Netmarble
The game leverages Studio Ghibli's esteemed art style beautifully to create what many are saying is one of the most beautiful mobile games made to date. Can you talk about the work that went into nailing the game's visuals?
 
General Art Director Nam Ho Choi:
Our goal was to depict a beautiful world in warm, rich colors where players can expect exciting things to happen. We also focused on creating dynamic facial expressions and unique personalities for our characters so that they convey an anime sensibility. To achieve this goal, we approached this project not just as a game, but as an animated film that focused on expressing vividness across the entire project—from settings to characters.
 
Senior Character Concept Artist Hwan Kwon: The process of refining the visuals was the process of creation itself. Our experts in various fields did their best to design, render, modify, and create the scenes we imagined. Before finalizing, we reflected on whether this was the best work we could do. It was hard work, but I believe our efforts led to good results.

With expressive movements and slick cutscenes, Cross Worlds features animation befitting a world-class anime. Can you talk about the work that went into that?
 
Senior Animation Artist Ki Beom Lee:
In order for characters to clearly express their emotions, facial expressions that matched their personalities were constructed as part of the pose asset, and were used for cutscenes and dialogue to maintain consistent quality.
 
We utilized Unreal Engine's Sequencer and Animation Blueprints when making cutscenes. With these tools as the foundation, we also utilized the in-game Animation Sequence and other tools such as bone control to edit various essential resources. This helped us focus on producing dedicated animations used exclusively for the cutscenes.
 
Video Production Manager Kyo Jin Lee: In order to improve the quality of various secondary animations (dynamic animations, trailing, etc.), bone control nodes were used to correct any discontinuity between animations that occurred during production. It was also used to add rich secondary animations to various other objects.
 
In the case of the story cutscenes, we tried to strengthen them by checking the key points provided by the planning team. We took the feeling of the completed scene into consideration, and created scenes appropriate for the story with the right cut composition and emotionally resonant scenery.
Image courtesy of Netmarble
The game features diverse and detailed landscapes that range from peaceful grasslands to snow-covered fields. Can you talk about how the team executed designing the game's varied environments?
 
Senior Game Concept Designer Myung Sin Koo:
Due to the nature of mobile MMORPG games, it is difficult to show the scale of the landscape. To address this issue, we separated the matte painting or viewpoint space from the play space. This way, instead of focusing on the quality of small assets, we focused on environmental elements, levels, and the skyline of the wider field.
 
We were able to build a rich environment using various lighting and fog effects provided by Unreal Engine, and we tried to highlight the different locations by setting the main color lights differently for each field. It took a lot of effort to balance saturation and brightness so that they wouldn't be overwhelming to players.
 
These detailed tasks could be viewed in real-time in Unreal Engine, making it intuitive and efficient.

Cross Worlds has been praised for its fun and intuitive gameplay. Can you talk about your design philosophy there?
 
Oh:
MMORPGs, by design, often prioritize the fun experiences that players have together—to the detriment of the story elements that shape the world.
 
We wanted to deliver a complete story like a traditional JRPG, even though we were developing Ni no Kuni: Cross Worlds as an MMORPG.
 
While the majority of recent MMORPGs encourage players to build social relationships centered on competition, our systems and content have been designed to promote cooperation.
Image courtesy of Netmarble
Can you elaborate on your approach to the game's combat system?
 
Oh:
When we were developing the combat system, the most important thing  was how hits felt. Since an MMORPG has to receive the results of the decision from the server and express it on the client, there is inevitably a time difference while information is exchanged. To create precise action combat within this environment, we applied various techniques that we developed in our previous works. Furthermore, we have adopted non-targeting combat to deliver a refreshing feeling similar to hack-and-slash games.

New to the series, Ni no Kuni: Cross Worlds allows players to choose their own class that includes Witch, Rogue, Engineer, and more. Can you talk about your approach to designing them?
 
Oh:
When designing the five classes of Ni no Kuni: Cross Worlds, we used the main protagonists of Ni no Kuni: Revenant Kingdom as reference. We wanted each character to have their own unique look and personality. The more challenging content of Ni no Kuni: Cross Worlds doesn't require classes to have a specific role, such as a tank or healer. This is because we didn't want casual gamers who were captivated by the visuals of Ni no Kuni: Cross Worlds to experience disappointment when the class they picked didn't suit their playstyle.
 
Special care has been taken so that players can immerse themselves in the game as agents of action rather than observers. For example, if you play the game, you will find that the main character's dialogue is extremely restricted. If the main character speaks and acts against the will of the player, the role of the player changes to an observer, hindering game immersion.
 
However, the fact that the main character does not say a lot of lines is a big limitation in developing the JRPG story emphasized earlier. To solve this problem, we needed someone to lead the story on behalf of the player and this is where a charming character named Cluu was born. We could have made a compromise and moved on, but we chose not to do so.
Image courtesy of Netmarble
In addition to the various classes, Cross Worlds features robust character customization options that allow players to tweak height, clothing, hairstyle, and even individual eye color. Can you talk about the work that went in there?
 
Senior 3D Modeling Manager Kyung Hwan Han:
Body shape customization was done by adjusting the scale of the bones used in the skin rig. In addition, various hair assets were added to give players more options. The color of irises and outfits can be changed, and specific UV sections can be dyed in monotone. Various texture mask maps were added with dyeable material so that they could be dyed with a predetermined palette color.

What made Unreal Engine a good fit for the game?
 
Lead Client Programmer Tae Woo Kim:
Ni no Kuni's rendering uses traditional cartoon cel-shading. Furthermore, its sensibility relies on warm, Ghibli-inspired visuals.

Unreal Engine's Material Editor tool is powerful and has an intuitive UI and enables fast iteration, empowering us to reach our current visuals more quickly.

It’s also the only engine we’ve seen that can pull off massive battlefields where hundreds of characters are concentrated.

Even without modifying the engine, using these tools can lead to remarkable performance improvements. Since the full source code is provided, anyone can understand exactly how these optimizations work and quickly apply them.

There are many additional advantages to using Unreal Engine, such as the convenience of multi-platform support, strong UDN support, and plugin features.
Image courtesy of Netmarble
Did the team have any favorite UE tools or features?
 
Lead Client Programmer Tae Woo Kim:
Blueprint Editor, Sequencer, Persona, BehaviorTree, Material Editor, and Unreal Insights are all easy-to-use tools.
 
Each tool's preview feature greatly speeds up the development process.
 
In addition, the many debug tools are really useful. Among them, Blueprint Debugging, Collision Analyzer, and Visual Logger are all very helpful.
 
Specific features for each game can be easily extended with plugins, commandlets, or the Editor Utility Widget. For example, we created a plugin with editing tools for Familiar Adventure.
 
Thanks to Live Coding, fast iteration is possible. Being able to check the code after modifying it greatly improves productivity.

Considering Netmarble leveraged Unreal Engine for Lineage 2: Revolution, were there any ways that experience helped benefit Ni no Kuni: Cross Worlds?
 
Tae Woo Kim:
We were familiar with almost all of Unreal Engine’s tools because Lineage 2 Revolution also used UE.
 
We simply upgraded to a newer version of the engine to get additional functions that Epic Games has since added.
 
Ni no Kuni: Cross Worlds was built upon what we learned from working on Lineage 2: Revolution, and we saved a lot of time by going back to how we implemented features in that game. This allowed us to focus on quickly expanding and improving Ni no Kuni’s features.
Image courtesy of Netmarble
Considering how Ni no Kuni: Cross Worlds runs so smoothly, can you talk about how you optimized the game for mobile?
 
Tae Woo Kim:
In addition to the basic optimization techniques, we heavily utilized the Significance Manager and URO (Update Rate Optimization) functions provided by Unreal Engine.
 
Significance Manager, was used to determine the importance of each object, and it helped us determine the appropriate actions to take. The key areas of optimization were: 
  • Ignore unnecessary ticks
  • Show detail differences by the field of view and distance
  • Ignore certain animations and particles that spawn outside the field of view
  • Immediately change certain materials outside the field of view without storing
  • Group mini-map objects
  • Bypass frequent spawn/despawn of actors through caching
  • Check and inspect files through caching
  • Prevent creation of duplicate outline components, creating only on demand

Ni no Kuni: Cross Worlds has been praised for its smooth net code. Can you delve into how the team executed there?
 
Lead Server Programmer Hyun Koo Kim:
  1. Use the Unreal Engine pathfinder module even for the server.
  • When an NPC moves, the movement may be distorted if the pathfinder logic is different between the client and server.
  • To solve this problem, servers also import and use Unreal Engine's pathfinder module.
 
  1. Adaptive Sync Control Manager, which adjusts the movement synchronization cycle according to the number of users.
  • In the beginning, we collected and sent moving packets frame by frame for fear of performance issues.
  • Then, during development, we contemplated how to speed up the synchronization of movement during PVP.
  • We eventually came up with a solution where packets are sent immediately when there are few users, since it won't affect performance. When there are many users, the packets are collected, then sent to avoid performance issues.
 
  1. Object Retention System during Public/Instance World transition.
  • If the NPC that was in the public world was also used in the instance world, the previous object had to be recreated. This led to a rough spawn transition.
  • To solve this problem, the server delivered recycling information and the client recycled objects based on that info to ensure a smooth transition.
 
  1. Thread pool dedicated to outgoing packets.
  • Due to the nature of MMORPGs, many users will gather in one space. This situation causes the server to broadcast packets for movement and combat synchronization to many users.
  • In other words, from the server's point of view, there is less reception but more transmission. To solve this problem, we created a send-only thread pool to allow a large amount of packets to be sent.
 
  1. Predetermined Skill System
  • Mobile games suffer from unstable networks and are greatly influenced by network latency.
  • During development, we did not encounter this issue in the PC environment. However, when we tested in a mobile environment, we found out that the combat system did not feel as satisfying.
  • To resolve this issue, the server pre-determined damage at the beginning of the skill and sent the result packet to the client. The client would then reflect the result in the hit frame.
 
Thanks for your time. Where can people learn more about Ni no Kuni: Cross Worlds?

Oh:
You can find more info at https://ninokuni.netmarble.com/en.

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