Next month's Star Wars Republic Commando will take you behind the scenes of the Clone Wars as the leader of an elite squad of combat specialists. In our latest designer diary, John Hancock tells us about developing the unique AI that will drive you and your team to victory.
Search and Destroy: Squad Gameplay With Less Work, More FunBy John A. Hancock, Senior Engineer, Squad AI
Director Tim Longo already discussed in his designer diary how our “One Touch Squad” control was designed to provide the player with all of the fun of a squad game without all the work. Less work for the player often meant more work for the development team, and creating AI for friendly characters is one of the biggest challenges in game development today. As such, creating a successful squad experience for Star Wars: Republic Commando was an immense challenge for the entire development team, involving cooperation from level designers, sound designers, artists, animators, and programmers, but it has been hugely rewarding.
In many squad-based first-person shooters, the squad spends much of its time following the player and is thus out of the player’s field of view, sometimes so much so that the player is hardly aware of the squad at all. One of the top design priorities for the squad for Star Wars: Republic Commando was to make sure that the player is constantly aware of the squad, usually keeping them in front of the player: leading the way, but not getting in the way.
To eliminate micromanagement, some games exclude squad control entirely and script everything. However, we wanted the player to have the ability to control the squad through commands and contextual actions. Our squad is almost never scripted; it is always reacting to the environment and to the player behavior.
Out of these requirements, our “Search and Destroy” command was born. Search and Destroy is our default squad stance and puts the squad into action: the squad charges ahead of the player, led by a set of objectives for a level specified by the level designer. In this mode, the squad moves towards its next objective, taking up cover positions, fighting enemies, backing up the player while he performs an action, never moving too far ahead, always present. To avoid getting in the way, the squad takes up cover positions in a battle, knows to duck if they cross the player’s line of fire, and moves aside if nudged by the player.
Our Search and Destroy mode provides the goal-directed behavior of scripted squad experiences, but without the brittleness of strict scripted control. The player can always choose to have the squad do something else. If a player prefers to lead the squad into battle, the player can use the “Form Up” stance to have the squad follow him. In Form Up, the squad won’t fire unless either fired upon by enemies or the player starts firing their weapon. The “Secure Area” stance can be used to command the squad to take up positions near a player-specified location. We also have a wide variety of context-specific maneuvers the player can use in addition to the always-available basic stances.
To implement our vision, we constantly had to invent new AI technologies for Republic Commando. Traditional AI architectures didn’t gracefully handle the number and variety of behaviors we needed the squad to display, so we had to create new ones. We worked on novel methods to make scripting less error-prone and brittle. We developed new algorithms to help our wide variety of AI to navigate efficiently and effectively. We developed the most elaborate AI-driven voice system that we know of, consisting of thousands of AI-triggered lines categorized into over 180 different categories or cues.
We’re proud that our squad system is something fundamentally different than what’s gone before. It fulfills our vision of less work and more fun, and we hope you enjoy playing the game as much as we enjoyed making it.