Issue link: https://digital.copcomm.com/i/48986
Gaming n n n n and triple counters, whereby he deflects and dodges all these blows and sends counter- attacks [on multiple characters] in one swift move." The daunting task of programming AI for these complex ensemble fights and endless counterattacking fell to AI programmer Tim Hanagan and his team of coders. "There were so many challenges involved in increasing the crowd combat from 10 or 12 to about 30. First, we had to optimize the performance of all the various systems so that these large-scale fights could run at a consistent 30 frames per second," he says. "The second was managing the positioning of so many enemies, to pre- vent the fights from feeling too cramped." From a visual standpoint, the group had to allow the player to see clearly and assess each situation. Most of these challenges were ad- capacity to support more than 30 combatants in some areas, Hanagan cautions that pushing the crowd beyond that number only made the gameplay confusing. Batman is also armed with a new "context- sensitive mechanic," which allows him to in- tegrate his immediate environment into his fighting—improvising with a nearby railing, brick wall, pillar, or street lamp—to subdue as- sailants. These context-sensitive moves require code that could rapidly sample the local area to identify whether the surrounding geometry could be used within the current combat move, notes Hanagan. The problem with all systems like this, however, is trying to make sure that the developers balance the accuracy of the checks with the need for fast run-time performance. "You always want to minimize the number of line checks performed, but at the same time, character wants to interact with an item in the world, then a positional marker embedded in the animation tells the system how the charac- ter should be aligned. Of course, much of this complex interac- tion with Gotham's urban jungle (as Batman or Catwoman) involves scaling walls and ledges, climbing through sewers and ventila- tion ducts, trying to gain a precarious foothold or handhold on a cornice, gargoyle, crack, or crevice. For aligning hands to walls and ledges, Rocksteady used some of the Unreal Engine's built-in arm IK. However, the team tackled most of the challenge by building the environ- ments to standard grid sizes and then animat- ing to those sizes. So for a wall climb, there are separate animations for 128-, 256-, and 384- unit height walls, and if the animations don't quite match up to the real wall, then the artists would use a blend to shift the entire character. "For aligning the character to the floor, we dynamically calculate a virtual floor plane that approximates the actual floor geometry under- neath the character. A standard two-bone leg IK then skews the animation to fit the plane. In some situations, where leg IK is insufficient (like Catwoman crawling on the ceiling), we rotated the entire character to fit the virtual plane," says Rennie. Developers used Epic Games' Unreal Engine 3 and Autodesk's 3ds Max for the textures, geometry, and lighting. dressed through the studio's custom character collision system. Implemented within the Unreal engine, this character collision system replaces the existing stock Unreal system with one that's much faster, more efficient, and streamlined. Hanagan explains: "It uses the navigation mesh data to allow faster collision queries against an approximation of the real-level ge- ometry. This was a major contributing factor in allowing us to support so many active char- acters at once." The team additionally implemented a real- time path-smoothing system to improve the look and realism of the paths the AI take when traversing levels. In addition, they developed a character scripting system within the Unreal Kismet scripting editor to allow animators to implement complicated scripted events with- out any code support—all this while still al- lowing for a high level of player interaction. While the character collision system has the you don't want to end up performing a wall animation on a 10 cm-wide lamppost, or end up slamming a thug's head into what should be a railing but, in reality, is the space between two railing-high benches," he says. In building this robust combat system, Rennie contends that the most important thing wasn't any particular piece of technol- ogy, but the animators, gameplay coders, and tech artists all sharing the same studio space and collaborating closely. Beyond this close collaboration, Rocksteady's artists relied on the studio's own animation blending system, which harnesses all the standard tools and techniques. This includes cross-blending, time warping, additive animation, motion extrac- tion, and mirroring. A particular focus was placed on automatically aligning animations. For example, if two characters are interacting with each other, the system will automatically blend them into the correct position based on their relative positions in the animation. If a Dark Knight Rising Indeed, Rocksteady's commitment to story- telling, high production values, and acting— both animated and mocapped—has delivered the studio to the forefront of the industry's leaders, and Arkham City to the forefront of contenders for Game of the Year. At this year's Comic-Con, Hamill, Conroy, and Dini held court on a panel that was one of the conven- tion's biggest draws, no small feat considering the presence of Peter Jackson and Steven Spiel- berg pushing Tintin. And it's all by design, too, for the seeds of Arkham City were laid, like Chekov's gun, in secret plans hidden in a backroom of warden Sharp's office two years ago in Arkham Asylum. Who knows what little bread crumbs have been dropped for future sequels in Gotham's mean streets. Only Rocksteady knows. What's certain is that the developer's achievements left fans waiting with bated breath for this sequel, and if Rocksteady holds fast to its resolve of pushing the bar higher and higher, The Guinness Book of Records may find itself passing the mantle again…and again. n Martin McEachern is an award-winning writer and contributing editor for reached at martinmceachern@hotmail.com. December 2011/January 2012 47 He can be Computer Graphics W orld.