Olympus' Chosen is a multiplayer action-adventure game with a "souls-lite" design that invites players to traverse an open world and engage in combat with Greek mythology-inspired creatures alongside their companions. This game is being solo-developed and remains in development, with no definitive release date. Notably, the multiplayer component of Olympus' Chosen boasts dedicated server implementation via the Riptide network library.
Client-side Prediction, Server Reconciliation, and Entity Interpolation
In order to ensure seamless and equitable player versus player and player versus environment combat in Olympus' Chosen, I have incorporated a number of key technical features. These include client-side prediction, server reconciliation, and entity interpolation. In order to implement these features, I had to shift away from my previous physics-based character movement approach, as Unity's physics system is non-deterministic. Through the creation of a customized tick system, I have been able to effectively manage all aspects of client prediction and reconciliation within the foundational Player class.
For interpolation, the functionality can be found in the CharacterInterpolator and PlayerInterpolator classes.
Network Messaging
Custom Animation System
Furthermore, given the unique style of Olympus' Chosen, I was compelled to develop a custom animation system. This system was imperative for accurate prediction of other players' positions, particularly when initiating a root motion animation, as well as to ensure effective reconciliation. This was necessary as Unity's standard system struggles with halting and returning to a previous point mid-animation, particularly when returning to a finished animation.
To address this challenge, I utilized Animancer, a plugin available via the Unity Asset Store, which enabled me to manage the visual components of animation replaying. However, to achieve optimal results, significant custom functionality was required. In particular, I created two custom datatypes: Animation Info and Animation Action, which are the base for this system.
Animation Info
This class utilizes Unity’s scriptable objects system and stores a lot of information including the actual animation clip, the delta positions, and the Animation Actions.
Tools
Moreover, I designed a customized editor script that presents a timeline of an animation, simplifying the process of adding Animation Actions with ease.
Animation Action
This replaces Unity’s built in animation events system. That way we can fire off the same commands at the same point in the animations every time.
Additionally, I created a specialized testing scene that incorporates a DeltaPositionsRecorder class, which simplifies the process of recording and playback testing of delta positions on Animation Infos.
Perfect Sync
Furthermore, the development of this custom animation system was crucial for addressing lag compensation issues. This is achieved by the following, when a player initiates an animation and the "IsTimeSensitive" Boolean is activated, non-local players will skip to the same point in the animation as the server, based on the client's current ping and tick. This ensures that both the client and server remain perfectly synchronized during spatially critical animations involving other players or NPCs. As a result, the occurrence of mispredictions by clients is significantly reduced. Prior to implementing this system, I experienced a high number of mispredictions on moving targets, which posed a significant challenge that this solution successfully addressed.
Attacks and Combos
In addition, the game features three different types of attacks - light, heavy, and charge. To manage the information for each of these attacks, I developed an Attack scriptable object class that stores all necessary data. Within the Attack class, three other attacks can be stored to reflect the combo possibilities following a given attack, each corresponding to the type of attack the player attempts next.
Light Attack into a Light Attack
Light Attack into a Charge Attack
Combat Design
In many games, melee combat can often feel tedious or uninteresting, often due to issues with parrying and stun-locking. For this game, I aimed to avoid these pitfalls by adhering to a specific design principle - combat is like a dance. What I mean by this is that combat should have a give-and-take dynamic with an ebb and flow to it. When players engage in combat, they should be searching for openings to strike quickly, before retreating to safety and looking for their next opportunity. In most cases, fights shouldn't be determined by the first exchange, with the exception of particularly strong or weak enemies. I want to avoid a combat system where players simply wait for their enemies to attack, pressing a dodge, block, or parry button. This would be unappealing to our audience, who are more active and engaged players.
Additionally, I want our combat system to reward skill and practice, much like learning a dance. Players should be able to react more quickly and learn to recognize attack animations, allowing them to progress in the game. However, I also recognized that not all players in our audience are highly skilled at video games. Therefore, it is important that the combat system has a surface level that is relatively simple and easy to grasp, while still allowing for more advanced techniques to be mastered over time.