protected override Vector2 CalculateForce()
{
if (_menace == null || (Vehicle.Position - _menace.Position).sqrMagnitude > _sqrSafetyDistance)
{
return(Vector2.zero);
}
// offset from this to menace, that distance, unit vector toward menace
var position = Vehicle.PredictFutureDesiredPosition(_predictionTime);
var offset = _menace.Position - position;
var distance = offset.magnitude;
var roughTime = distance / _menace.Speed;
var predictionTime = ((roughTime > _predictionTime)
? _predictionTime
: roughTime);
var target = _menace.PredictFuturePosition(predictionTime);
// This was the totality of SteerToFlee
var desiredVelocity = position - target;
return(desiredVelocity - Vehicle.DesiredVelocity);
}
protected override Vector2 CalculateForce()
{
if (_quarry == null)
{
enabled = false;
return(Vector2.zero);
}
var force = Vector2.zero;
var offset = _quarry.Position - Vehicle.Position;
var distance = offset.magnitude;
var radius = Vehicle.Radius + _quarry.Radius + _acceptableDistance;
if (!(distance > radius))
{
return(force);
}
var unitOffset = offset / distance;
// how parallel are the paths of "this" and the quarry
// (1 means parallel, 0 is pependicular, -1 is anti-parallel)
var parallelness = Vector2.Dot(Vehicle.Forward, _quarry.Forward);
// how "forward" is the direction to the quarry
// (1 means dead ahead, 0 is directly to the side, -1 is straight back)
var forwardness = Vector2.Dot(Vehicle.Forward, unitOffset);
var directTravelTime = distance / Vehicle.Speed;
// While we could parametrize this value, if we care about forward/backwards
// these values are appropriate enough.
var f = OpenSteerUtility.IntervalComparison(forwardness, -0.707f, 0.707f);
var p = OpenSteerUtility.IntervalComparison(parallelness, -0.707f, 0.707f);
float timeFactor = 0; // to be filled in below
// Break the pursuit into nine cases, the cross product of the
// quarry being [ahead, aside, or behind] us and heading
// [parallel, perpendicular, or anti-parallel] to us.
switch (f)
{
case +1:
switch (p)
{
case +1: // ahead, parallel
timeFactor = 4;
break;
case 0: // ahead, perpendicular
timeFactor = 1.8f;
break;
case -1: // ahead, anti-parallel
timeFactor = 0.85f;
break;
}
break;
case 0:
switch (p)
{
case +1: // aside, parallel
timeFactor = 1;
break;
case 0: // aside, perpendicular
timeFactor = 0.8f;
break;
case -1: // aside, anti-parallel
timeFactor = 4;
break;
}
break;
case -1:
switch (p)
{
case +1: // behind, parallel
timeFactor = 0.5f;
break;
case 0: // behind, perpendicular
timeFactor = 2;
break;
case -1: // behind, anti-parallel
timeFactor = 2;
break;
}
break;
}
// estimated time until intercept of quarry
var et = directTravelTime * timeFactor;
var etl = (et > _maxPredictionTime) ? _maxPredictionTime : et;
// estimated position of quarry at intercept
var target = _quarry.PredictFuturePosition(etl);
force = Vehicle.GetSeekVector(target, _slowDownOnApproach);
#if ANNOTATE_PURSUIT
Debug.DrawRay(Vehicle.Position, force, Color.blue);
Debug.DrawLine(Quarry.Position, target, Color.cyan);
Debug.DrawRay(target, Vector2.up * 4, Color.cyan);
#endif
return(force);
}