Blaster
About the Project
Blaster was the second project I started in order to learn as much of Unreal Engine 5 as I could, focusing on learning fundamental multiplayer mechanics and maintaining correct server authority whilst simultaneously filling gaps in my existing C++ and UE5 knowledge. To build these valuable skills, I followed a course on Udemy with the goal of understanding everything I was doing, making sure I wasn’t just blindly copying someone else’s work and learning nothing.
This turned out to be a very effective learning style and resulted in a multiplayer shooter game with multiple game modes, and a standalone, re-usable multiplayer plugin that seamlessly works with Steam. Finally, a big focus in this project was learning to code the right way, learning to write code that doesn’t just compile, but to craft clean, efficient, and maintainable code.
I would also like to thank Stephen Ulibarri for creating such a thought-out course.
Development Overview
Multiplayer Plugin
In an effort to understand exactly how my entire project worked and gain insight and experience into how multiplayer games work, I decided to learn how to code a multiplayer plugin first. This meant making my own multiplayer sessions subsystem which I based off of the game instance for persistent sessions, safe server travel, correct lifetime and easy access through the game instance.
Delegate and Async Communication
The subsystem also taught me how to create dynamic multicast delegates as well as their importance in cases where there could be delays in retrieving necessary information. For example when a player clicks the join button on the main menu, that calls a function on the subsystem that searches for suitable sessions through the online session interface, which broadcasts the result of that search once complete, a broadcast that is bound to by another function in the subsystem, which broadcasts the results with a custom delegate back to the menu that can correctly select and join a session.
Matchmaking and Session Filtering
The menu is where all of the match type information is stored and game mode selection takes place after the find session delegate has been broadcast. Here, all the search results are filtered through until one is found with a match type that matches the desired game mode, which is automatically joined. After this process, if no suitable session is found and joined, the join button is enabled allowing players to search again.
Steam Integration and Networking
Furthermore, I decided to make my plugin work using Steam and its network features, meaning my game doesn’t rely on peer to peer connections. This means that not only does it automatically use peoples steam usernames rather than needing separate account creation, as well as significantly more security for players and their IP addresses.
Finally, I ensured that this plugin was disconnected from any game specific logic making it fully re-usable with scalable architecture if required for future projects.
Lag Compensation
A big problem in multiplayer games, especially fast-paced shooters, is lag. This simply means a delay between the player’s local actions and the server receiving information about those actions because of network travel time. In shooters, this can mean lining up your crosshairs, clicking to take a shot, however the shot is delayed and the target has moved by the time it is fired. This leads to a very poor experience for the player and in extreme cases can make the game impossible to play.
Server-Side Rewind
However, there are a number of ways to reduce or even eliminate these issues, one of which is server-side rewind. This is where the player tells the server what time it requested an action, allowing the server to look back in time and see if it would have been successful had there been no delay. For firing a weapon, this means the server keeps a custom frame package containing time and location, as well as an array of hitboxes for every player every frame. This allows it to compare the player’s hit location with the hit boxes for the provided time of impact and check whether there was a valid target before applying damage.
Interpolation, Hit Validation and Scatter Replication
To make this system even more accurate the server doesn’t just compare the hit location to the frame package with the closest time, it interpolates the correct amount between the two closest frames to recreate the hitboxes as accurately as possible without relying on client information that could be faked by cheaters. In a further effort to stop cheaters, the hit location is also calculated by the server either with its own line trace or projectile path prediction depending on weapon types. Finally, this includes scatter replication for weapons like SMGs or shotguns, where calculating a different scatter direction could cause incorrect hit validation leading to a bad player experience.
Client-Side Prediction
Client-side prediction is another method to make the game more responsive by reacting to the player’s inputs immediately, and then allowing the server to correct it later if necessary. In Blaster this came in the form of playing fire effects and animations as soon as the input was received, as well as instantly updating the ammo count in the HUD, all to make the game feel more responsive for players. However since this is not controlled by the authoritative server, it is not used on anything that alters gameplay like damage to minimise the methods possible to cheat with.
Gameplay
Aside from basic movement, weapons were one of the most important mechanics in this project which meant they needed a lot of attention and variation. This meant perfecting the visual element of playing accurate animations depending on the held weapon and ensuring correct placement of both hands throughout those animations. It also meant that, considering how often they would be interacted with, they should all feel slightly different which led to multiple weapon types including hitscan and projectile, which was further developed to allow explosives. Furthermore, with differing damage between weapons and headshot recognition, as well as bullet scatter and velocity, every weapon feels unique and exciting.
Health and Shield
Now that players could be shot, they needed a measure of survival leading to the integration of a health system. This was represented on the HUD and adds layers of risk, skill and decision making to the gameplay, resulting in a more engaging experience for the player. To emphasize these values I decided to make health unable to regenerate, making it much more valuable but also making the game feel overly punishing. This led to the addition of shield. This is extra health that can be collected and refilled during combat leading to much faster game pacing and more strategic options for the player to weigh during combat.
Powerups
Next I wanted even more features that improved the pacing of the game whilst giving it more of a unique identity from every other multiplayer shooter game. I decided that powerups were the answer, a way to temporarily make a player much more powerful giving more options to attack, defend and plan strategy around. This included mechanics like super-jump, super-speed, and shield refill. These are all able to completely change a player’s odds in an encounter whilst being balanced with their temporary nature leading to a fun experience for the player. Finally these are not always available to increase their value and instead appear at spawners scattered around the map. These spawners trigger at random times and intervals, creating a random powerup to be picked up by the player. Also to ensure they are easily recognisable, each powerup is represented by a unique system that can be deciphered quickly in the heat of combat.
Weapon-Specific Ammo and Reloading
To bring back some resemblance of reality, I decided to add ammo. This meant that unlike many movies, players would run out of bullets eventually and have to choose when to reload their weapon before their magazine was empty and their reload was triggered automatically. This system was then expanded to include weapon specific ammo rather than a large generic pool which prompted strategic weapon usage in relation to how much ammo it had in reserve. Also, using a similar system of spawners to the powerups, reserve ammo could be randomly scattered around the map giving the player extra objectives while surviving. This also gave me extra options when it came to balancing the weapons, allowing me to alter their reload times and magazine capacities individually, which ultimately can be used to optimise gameplay pacing.
Game Modes
This game started out with just one game mode, Free-for-All. This was by far the easiest as anyone could just spawn anywhere, and shoot anyone. It was also the easiest to score as whoever got the most kills won. However being restricted to just one game mode felt repetitive and would lead to players losing interest in the game too quickly which led to the creation of a Team Deathmatch game mode. This added much more complexity to the spawning system as well as the scoring, however it added much more depth than just shooting mechanics. It fundamentally encouraged teamwork and coordination as a result of shared scoring and made a completely different experience from the same core mechanics. Finally I added a Capture the Flag game mode. This combined the team-based mechanics from Team Deathmatch with a much clearer single objective that encouraged teamwork and coordination even more, even adding the options for role differentiation. This truly changed the feel of the game once more and gave the player a broad range of options to decide what pacing they want, which makes them less likely to get bored of the game.