Jordan and Tom's Flocking Project - Zombie Flockalypse

Click here to load the demo
You may also view the source code here
Note that the demo does require Java. We've fought long and hard with processing.js and decided to bail after user input disappeared.

Zombie Flockalypse is a single player top down shooter, where your objective is to rescue at least 50 humans in 2 minutes.
The zombies and humans are controlled by flocking systems to determine their movement.

Player Controls:

WASD for standard up,left,down,right movement.
Mouse to aim and click to shoot zombies.
F to get nearby humans to follow you. Lasts 10 seconds unless you hit it again.

Game logic:

Zombies and humans are randomly dispersed around the city when the game starts.
Zombies are green, humans are gray, the player is a light blue.
Your objective is to get at least 50 humans to follow you into the "Safe Room", a blue box that the zombies have a hard time getting into.
Note that the humans may randomly walk into the safe zone on their own, but it's easier for them to know where to go if you beckon them to follow with 'F'.
If a zombie is killed, a new 'boid' will spawn on the edge of town. 80% chance to be human, 20% to be another zombie.
If a human is killed or saved, a new human will spawn on the edge of town.
If the player kills a human, he will suffer a speed loss due to grief
If a human is touched by a zombie, he or she turns into one.
If a player is touched by a zombie, they are killed and will respawn in the Safe Room.

The zombies and players are controlled by flocking AIs which blend weighted "force vectors" into the velocity they use on their next frame update. Zombies are forced to have a slightly slower max velocity than humans and both are slower than the player's max speed. Because we're blending a lot of vectors with weights, it's sometimes possible for a zombie to "jump the wall" and get into the safe room, effectively ruining everyone's day.
All of the available behaviors that we've coded and added should be visible in game. The grouping AI for humans has been tuned very low to prevent them from forming death packs when zombies get too close.
In blending the behaviors, we often came across instances where something would mess up hard. For instance, the humans would group up too much and cohesion/grouping vectors would negate their fleeing vectors and the poor guys looked like they were panicing before getting munched by zombies. It looks sort of cool, but they jittered around too much and it took away from the possiblity of actually winning the game. Also, if the group distance is too large, the humans would tend to sit and spin in a circle with each other until they were eaten.
The wall avoidance behavior was also tricky. It was tweaked so it was stronger the close you were to the wall. We ran into issues where zombies would run so hard during a chase that they'd manage to break the wall avoidance and "jump the wall". As both players and boids are limited to the edges of the level, this really only comes up in the safe room. Suffice it to say, the zombie needs to be chasing a human really hard to break into it. It's still possible as we're not doing collision math on walls, we're just giving a "push" vector away from a wall the closer they get.
As we're blending behaviors, the limits we set aren't exactly "hard" limits. Cohesion should keep zombies and players about 25 pixels away from each other.
Predator and prey also works on a limited level. Both are at 100 pixels. Zombies won't chase and Humans won't run when they aren't in each other's range.
Finally, humans will only follow players if the player is within 75 pixels.

Flocking AIs for Zombies:

Cohesion - don't get too close to other zombies.
Predator - chase the nearest human(or player). If the prey gets too far away, it gives up.
Obstacle avoidance - Zombies will avoid walls - namely the edges of the level and the safe room.
Does not have any form of Grouping as these are mindless zombies.

Flocking AIs for Humans:

Cohesion - avoid getting too grouped up with other humans.
Prey - avoid zombies like the plague
Grouping - Form packs with nearby humans (small enough radius so they don't all create one giant pack).
Following - if the player hits 'F', the humans will follow the player for 10 seconds, unless he gets too far away.
Wall avoidance - the edges of the level.

Performance:
Performance doesn't seem to be much of a problem with zombies + humans = 100 boids on any modern CPU. It slightly chops on my 5 year old home computer, but that could just be fun with 64-bit java (Tom). Above those numbers, the game can run, but it become unplayable. Zombies will win and the player can't keep up.
Tom thinks there might be something useful in gridding the level to queue up boids that are local as none of the behaviors are global. Right now, each boid update is comparing itself to every other boid for checks, making the update process n^2. Gridding might help, but maintaining a grid with 100 boids on it will probably counterbalance any gain. Right now, we just "if away" anything out of range as we check each boid against the updating boid.