/// <summary>
/// Should the force be calculated?
/// </summary>
/// <returns>
/// A <see cref="Vector3"/>
/// </returns>
protected override Vector3 CalculateForce()
{
if (_path == null)
{
return(Vector3.zero);
}
// our goal will be offset from our path distance by this amount
float pathDistanceOffset = (int)_direction * _predictionTime * Vehicle.Speed;
// predict our future position
Vector3 futurePosition = Vehicle.PredictFuturePosition(_predictionTime);
// measure distance along path of our current and predicted positions
float nowPathDistance = _path.mapPointToPathDistance(Vehicle.Position);
float futurePathDistance = _path.mapPointToPathDistance(futurePosition);
// are we facing in the correction direction?
bool rightway = ((pathDistanceOffset > 0) ? (nowPathDistance < futurePathDistance) : (nowPathDistance > futurePathDistance));
// find the point on the path nearest the predicted future position
// XXX need to improve calling sequence, maybe change to return a
// XXX special path-defined object which includes two Vector3s and a
// XXX bool (onPath,tangent (ignored), withinPath)
mapReturnStruct tStruct = new mapReturnStruct();
_path.mapPointToPath(futurePosition, ref tStruct);
// no steering is required if (a) our future position is inside
// the path tube and (b) we are facing in the correct direction
if ((tStruct.outside < 0) && rightway)
{
// all is well, return zero steering
return(Vector3.zero);
}
else
{
// otherwise we need to steer towards a target point obtained
// by adding pathDistanceOffset to our current path position
float targetPathDistance = nowPathDistance + pathDistanceOffset;
Vector3 target = _path.mapPathDistanceToPoint(targetPathDistance);
// return steering to seek target on path
return(Vehicle.GetSeekVector(target));
}
}