Programming advanced AI is only part of the equation for game developers - players have to actually appreciate the intelligence of their enemies in order for it to have value; for it to be fun. Today, we’re looking at how animation and audio are being used to accentuate great AI.
Because intelligent characters have to look clever too…
Alex Champandard: AI coder, author and blogger (http://aigamedev.com)
Remco Straatman: Lead AI programmer, Killzone 2
Louis Gascoigne: Software Engineer, Dead Space, EA Redwood Shores
Owen O’Brien: Senior Producer, Mirror’s Edge, DICE
Alex Champandard: There’s a lot of research in academia that focuses on better animation, including motion planning and parametric animations. Games like Full Spectrum warrior use motion planning, the process of connecting animation clips together to reach a goal, whereas titles like Splinter Cell and GTA 4 use continuous parametric animations to feel more responsive. The interface between the AI and animation is problematic because it requires finding a balance between responsiveness and motion quality; compromising either results in problems for the game.
We’re only at the infancy of animation in the games industry, but now we have the computation power, the budgets to acquire the motion capture, and the research to back us up, it’s going to be an exciting few years.
(Further reading here)
Remco Straatman: The coupling of animation and AI is very important: animation is the clearest way for NPCs to express their intentions. We tied the AI and animations together in numerous ways: the alertness of the NPC influences their movement animations, the facial animations of NPCs change based on their state and their current action. NPCs use gestures and speech as part of their behavior.
We’re also making more use of special movement animations such as jumping over things, climbing up things, using ladders etc. These allow the NPCs to make better use of the terrain. Special animations are also tied in with specific behaviors, such as fleeing from grenades with the classic Hollywood desperation dive at the end.
Louis Gascoigne: For realistic story-based games it may be that the most critical thing to get right is the intersection of AI, animation and audio. The only way the player can appreciate the tactics of a sophisticated AI unit is if the player can see, hear, and understand the decisions being made.
In Dead Space because the Necromorphs do not speak this was particularly challenging as many of the clichés like, “Take cover!” can’t be used. The team struggled a bit with some of the cooler AI features like vent usage. In the end we ended up having audio logs, video logs, and graffiti in the environment that pointed out that the Necromorphs were moving using the vents. It happens to show up enough in the game that people recognize it fairly early.
Also, the Swarm enemies in Dead Space use a flocking behavior which looks quite nice in the final product.
Owen O’Brien: I think animation is absolutely key to the believability of AI characters. More important in fact than the amount of actual “intelligence” they have. Even people who should know better perceive well-animated enemies as more intelligent, even if the underlying AI decision making system is identical. It’s just human nature - a good animation will imbue even the most basic AI with a humanity that the player will then subconsciously extrapolate to more intelligent behaviour.
Come back tomorrow for the next part…