/// <summary>
/// Checks for intersection of the given spherical obstacle with a
/// volume of "likely future vehicle positions": a cylinder along the
/// current path, extending minTimeToCollision seconds along the
/// forward axis from current position.
///
/// If they intersect, a collision is imminent and this function returns
/// a steering force pointing laterally away from the obstacle's center.
///
/// Returns a zero vector if the obstacle is outside the cylinder.
/// </summary>
/// <param name="vehicle"></param>
/// <param name="minTimeToCollision"></param>
/// <returns></returns>
public override Vector3 CollisionAvoidance(VehicleActor vehicle, float minTimeToCollision)
{
// minimum distance to obstacle before avoidance is required
float minDistanceToCollision = minTimeToCollision * vehicle.Velocity;
float minDistanceToCenter = minDistanceToCollision + Radius;
// contact distance: sum of radii of obstacle and vehicle
float totalRadius = Radius + vehicle.BoundingSphereRadius;
// obstacle center relative to vehicle position
Vector3 localOffset = Position - vehicle.Position;
// distance along vehicle's forward axis to obstacle's center
float forwardComponent = Vector3.Dot(localOffset, vehicle.Forward);
Vector3 forwardOffset = vehicle.Forward * forwardComponent;
// offset from forward axis to obstacle's center
Vector3 offForwardOffset = localOffset - forwardOffset;
// test to see if sphere overlaps with obstacle-free corridor
bool inCylinder = offForwardOffset.Length() < totalRadius;
bool nearby = forwardComponent < minDistanceToCenter;
bool inFront = forwardComponent > 0;
// if all three conditions are met, steer away from sphere center
return(inCylinder && nearby && inFront ? offForwardOffset * -1 : Vector3.Zero);
}
/// <summary>
/// Check if a a specific vehicle has hit an obstacle, and return the point of collision. Returns Vector3.Zero if no collision detected.
/// </summary>
/// <param name="vehicle"></param>
/// <returns></returns>
public override Vector3 HasCollided(VehicleActor vehicle)
{
// contact distance: sum of radii of obstacle and vehicle
float totalRadius = Radius + vehicle.BoundingSphereRadius;
// obstacle center relative to vehicle position
Vector3 localOffset = Position - vehicle.Position;
// distance along vehicle's forward axis to obstacle's center
float forwardComponent = Vector3.Dot(localOffset, vehicle.Forward);
Vector3 forwardOffset = vehicle.Forward * forwardComponent;
// offset from forward axis to obstacle's center
Vector3 offForwardOffset = localOffset - forwardOffset;
// test to see if sphere overlaps with obstacle-free corridor
bool inCylinder = offForwardOffset.Length() < totalRadius;
// if inCylinder, return point of impact, else return zero
return(inCylinder ? offForwardOffset : Vector3.Zero);
}
public abstract Vector3 HasCollided(VehicleActor vehicle);
public abstract Vector3 CollisionAvoidance(VehicleActor vehicle, float minTimeToCollision);
/// <summary>
/// Check if a a specific vehicle has hit this obstacle, and return the point of collision. Returns Vector3.Zero if no collision detected.
/// </summary>
/// <param name="vehicle"></param>
/// <returns></returns>
public override Vector3 HasCollided(VehicleActor vehicle)
{
return(Vector3.Zero);
}
/// <summary>
/// Checks for intersection of the given cube obstacle with a
/// volume of "likely future vehicle positions": a cube along the
/// current path, extending minTimeToCollision seconds along the
/// forward axis from current position.
///
/// If they intersect, a collision is imminent and this function returns
/// a steering force pointing laterally away from the obstacle's center.
///
/// Returns a zero vector if the obstacle is outside the cube.
/// </summary>
/// <param name="vehicle"></param>
/// <param name="minTimeToCollision"></param>
/// <returns></returns>
public override Vector3 CollisionAvoidance(VehicleActor vehicle, float minTimeToCollision)
{
return(Vector3.Zero);
}