/** Rule of Cohesion.
** @param bj Pointer to the boid
** @return The velocity vector for Cohesion
**/
vector Cohesion(Boid* bj){
vector c = NullVector();
It itb = flock->getIter();
List boids = flock->getBoids();
Boid* tmp;
for (itb = boids.begin(); itb!=boids.end(); itb++) {
tmp = &(*itb);
float d = 1 + Norm(Diff(bj->getPos(), tmp->getPos()));
if (bj->getID() != tmp->getID() && d < 20)
c = Add(c, Mult(tmp->getPos(),1/(2*d*d)));
}
c = Mult(c,(float(1)/float(boids.size()-1)));
return Diff(c,bj->getPos());
}
/** Rule of Alignment.
** @param bj Pointer to the boid
** @return The velocity vector for Alignment
**/
vector Alignment(Boid* bj) {
vector mspeed = NullVector();
It itb = flock->getIter();
List boids = flock->getBoids();
Boid* tmp;
for (itb = boids.begin(); itb!=boids.end(); itb++) {
tmp = &(*itb);
float d = 1 + Norm(Diff(bj->getPos(), tmp->getPos()));
if (bj->getID() != tmp->getID() && d < 20)
mspeed = Add (mspeed, Mult(tmp->getSpeed(),1/(d*d)));
}
mspeed = Mult(mspeed,(float(1)/float(boids.size()-1)));
return Diff(mspeed,bj->getSpeed());
}
