Ninja AI

April 9, 2008 11:41 pm Sir Haxington Game Development

I’m not talking about Ninja Gaiden or Tenchu Z. Nope, I’ve been seeing Ninja AI in many games I’ve been playing lately. Ninja AI are simply AI that move from one place to the next in a blink of an eye. That’s all good if you have some crazy robot that teleports itself around, or ghosts that phase from one place to the next, but it’s buggy and annoying when humanoid AI that are supposed to move around semi-realistically end up darting around, swapping from one animation to the next in a single frame.

The worst offender is when AI is in the middle of a run cycle and decides to do a 180 and run in the opposite direction. It’s 10 times worse when the AI is leaning forward. Why? Well, as shown above, the player has just undergone heavy fire, dispatched every bad guy in his vicinity and is now taken a second to line up his shot. His finger is on the trigger, ready to take down that last asshole. Now, if the AI is behaving semi-realistically and decides to turn around, he’ll transition into a stop pose, then blend into running the opposite direction. This gives the gamer a chance to anticipate the AI’s directional change, or at least take a pot shot and possibly still hit the target. Even if the player misses, he’ll have some idea of where the AI will end up, can line up his shot accordingly, fire, and take the guy down. What a great reward for playing the game with some skill.

Now, Ninja AI ruin this reward. Go back a few seconds but assume that AI in a Ninja AI. The player has endured a long fight and is about to end it with a final shot. The AI is in the open, and decides to turn around and find cover. The player lines up his shot and fires. Miss! On the frame the player decided to fire, the AI has done a complete 180 and it running full tilt in the other direction. Also, the AI was leaning forward, so his head is already 3 feet in the opposite direction. The player alters his aiming to fire, but its still 1-2 feet off, because he didn’t compensate for the huge amount of distance his target has traveled in a single frame. The AI is still headed for cover, but the player over compensates and misses again. By this time, the AI is back in cover, and the fight is drawn out.

Really, it’s just a case of poor animation blending and transitioning. Sometimes I see this happen when an AI is behind cover. He’ll pop from his “exposed” animation to his “behind cover” animation in a single frame. It’s annoying as hell.

Some people will argue that Ninja AI behavior is a good thing, because it potentially extends game play. Unfortunately, it extends crappy and frustrating gameplay. Not only do Ninja AI look bad, but they are frustrating and unrealistic to fight against. Really, the game developers can fairly easily remedy the problem (assuming they have animators, some sort of blending system, and time) by simply adding transitions and blends when the AI decides to alter course. I think it’s much rather to make the game a little shorter and reward the player for skill, rather than make the game longer, potentially piss the player off, and reward the player for firing sloppily.

Also, if developers couple Ninja AI with AI that have ass-loads of health, prepare for a night of controller throwing and TV shattering!