Introduction:

(In general) 3D Flocking is:

• Discovering/balancing as many group characteristics of a particular creature that exhibits
  flock (or flock like) behavior as possible, in order to accurately represent groups of it.
• A problem of enforcing conditions that are required for flocking to occur.
• And of course a problem of 3D math.

Understanding the problem(s):

• Q: What conditions are necessary for a flock to occur?
  • A: Proximity.
    The units must *consistantly* be close enough to see each other such that they can take what
    the other nearby units are doing into account. If we just let a bunch of flockers go, they
    will eventually (1) Go off into the distance and (2) Split into subflocks that will most
    likely never re-unite (illustrated below.)
    
  • Solution:
    Keeping proximity

Solving the problem(s):

• Keeping proximity:
  • Migration rule: If a flocker can't see any other flockers, then it is oriented towards
    a waypoint in a set of way points that have been setup.
  • Sphere containment rule.
• Accurate behavior:
  • Average heading rule: keep each unit facing the same direction as it's neighbor flockers.
  • Average position rule: Direct each unit's orientation towards the center of it's neigbor
    flockers.
  • Seperation rule: Direct each unit's orientation away from neighbor flockers that are too close
    (aka. Probably going to be occupying the same space in short order--because we moved into them,
    they into us, or both.)
• Wild flipping:
  • This is one of the harder things to see when you don't know why it's happening and have not
    encountered it before.
• Distorted frames:
  • Re-determine a mutually orthogonal frame of basis axis-vectors, for each flocking unit consistantly.
    This can be done every frame of the game, or in a seperate thread every on a fixed time interval. The process
    for doing this is the same process that one might use to determine the basis axis-vectors of a camera, referred to
    as the Frenet frame.