//------------------------------ Pursuit ---------------------------------
//
// this behavior creates a force that steers the agent towards the
// evader
//------------------------------------------------------------------------
public Vector2D Pursuit(MovingEntity evader)
{
//if the evader is ahead and facing the agent then we can just seek
//for the evader's current position.
Vector2D ToEvader = evader.Pos - m_parentMovingEntity.Pos;
double RelativeHeading = m_parentMovingEntity.Heading().Dot(evader.Heading());
if ((ToEvader.Dot(m_parentMovingEntity.Heading()) > 0) && (RelativeHeading < -0.95)) //acos(0.95)=18 degs
{
return Seek(evader.Pos);
}
//Not considered ahead so we predict where the evader will be.
//the lookahead time is propotional to the distance between the evader
//and the pursuer; and is inversely proportional to the sum of the
//agent's velocities
double LookAheadTime = ToEvader.Length() /
(m_parentMovingEntity.MaxSpeed + evader.Speed());
//now seek to the predicted future position of the evader
return Seek(evader.Pos + evader.Velocity * LookAheadTime);
}
private void RenderVehicle(MovingEntity objVehicle, Graphics objGraphics, Pen objPen)
{
PointF pntLeft,pntFront,pntRight;
if (UseSmoothing)
{
Vector2D SmoothedPerp = objVehicle.SmoothedHeading().Perp();
pntLeft = (PointF)(objVehicle.Pos + (SmoothedPerp * objVehicle.BRadius));
pntFront = (PointF)(objVehicle.Pos + (objVehicle.SmoothedHeading() * (objVehicle.BRadius * 2)));
pntRight = (PointF)(objVehicle.Pos - (SmoothedPerp * objVehicle.BRadius));
}
else
{
pntLeft = (PointF)(objVehicle.Pos + (objVehicle.Side() * objVehicle.BRadius));
pntFront = (PointF)(objVehicle.Pos + (objVehicle.Heading() * (objVehicle.BRadius * 2)));
pntRight = (PointF)(objVehicle.Pos - (objVehicle.Side() * objVehicle.BRadius));
}
PointF[] points = new PointF[4];
points[0] = pntLeft;
points[1] = pntFront;
points[2] = pntRight;
points[3] = pntLeft;
objGraphics.DrawPolygon(objPen, points);
}
//------------------------- Offset Pursuit -------------------------------
//
// Produces a steering force that keeps a vehicle at a specified offset
// from a leader vehicle
//------------------------------------------------------------------------
public Vector2D OffsetPursuit(MovingEntity leader, Vector2D offset)
{
//calculate the offset's position in world space
Vector2D WorldOffsetPos = Utils.PointToWorldSpace(offset,
leader.Heading(),
leader.Side(),
leader.Pos);
Vector2D ToOffset = WorldOffsetPos - m_parentMovingEntity.Pos;
//the lookahead time is propotional to the distance between the leader
//and the pursuer; and is inversely proportional to the sum of both
//agent's velocities
double LookAheadTime = ToOffset.Length() /
(m_parentMovingEntity.MaxSpeed + leader.Speed());
//now Arrive at the predicted future position of the offset
return Arrive(WorldOffsetPos + leader.Velocity * LookAheadTime, (int)Deceleration.fast);
}
private void renderDetectionBox(MovingEntity objVehicle, Graphics objGraphics, Pen objPen)
{
List<Vector2D> points = new List<Vector2D>();
points.Add(new Vector2D(0, objVehicle.BRadius));
points.Add(new Vector2D(objVehicle.Steering().DBoxLength(), objVehicle.BRadius));
points.Add(new Vector2D(objVehicle.Steering().DBoxLength(), -objVehicle.BRadius));
points.Add(new Vector2D(0, -objVehicle.BRadius));
if (UseSmoothing)
{
points = Utils.WorldTransform(points, objVehicle.Pos, objVehicle.SmoothedHeading(), objVehicle.SmoothedHeading().Perp());
}
else
{
points = Utils.WorldTransform(points, objVehicle.Pos, objVehicle.Heading(), objVehicle.Side());
}
objGraphics.DrawLine(objPen, (PointF)points[0], (PointF)points[1]);
objGraphics.DrawLine(objPen, (PointF)points[1], (PointF)points[2]);
objGraphics.DrawLine(objPen, (PointF)points[2], (PointF)points[3]);
}
