public Point2D.Double getDirectionFor(Task task) {
Point2D.Double loc = task.ownerLoc;
Point2D.Double tLoc = task.targetLoc;
Point2D.Double tVel = task.target.getVelocity();
double tSpeed = tVel == null ? 0 : tVel.distance(0, 0);
Point2D.Double diff = new Point2D.Double(tLoc.x - loc.x, tLoc.y - loc.y);
if (tSpeed == 0 || task.owner.par.topSpeed < tSpeed * 1.0001)
return PlanarMathUtils.normalize(diff);
// In this algorithm, the capture point is assumed to be where the pursuer would first be able
// to overtake the evader if the evader kept heading
// in its current direction... this is where the ratio of speeds is equal to the ratio of
// distances to this hypothetical point.
// The evader's distance to this point is dE, and the pursuer heads toward the evader's
// position plus its heading times dE*leadFactor.
double mu =
task.owner.par.topSpeed / tSpeed; // ratio of speeds is used several times in the formula
double dcosth =
(tVel.x * diff.x + tVel.y * diff.y)
/ tSpeed; // basic dot product formula for cosine... provides ||diff|| * cos of angle
// between diff and tVel
double dE =
(Math.abs(dcosth) - Math.sqrt(dcosth * dcosth - (1 - mu * mu) * diff.distanceSq(0, 0)))
/ (1 - mu * mu);
return unitVectorTo(
loc,
new Point2D.Double(
tLoc.x + tVel.x * leadFactor * dE / tSpeed,
tLoc.y + tVel.y * leadFactor * dE / tSpeed),
task.type.multiplier);
}
public int compare(Point2D.Double a, Point2D.Double b) {
return Double.compare(a.distanceSq(center), b.distanceSq(center));
}