public Vector2 computeAlignment(NPC member)
{
Vector2 v = new Vector2();
int neighbourCount = 0;
foreach (NPC npc in Members)
{
if (npc != member)
{
float distSq = (npc.Position - member.Position).LengthSquared();
if (distSq < flockDist * flockDist)
{
v += npc.ComponentPhysics.Velocity;
++neighbourCount;
}
}
}
if (neighbourCount == 0 || v.LengthSquared() == 0)
return v;
v /= neighbourCount;
v.Normalize();
return v * alignmentWeight;
}
/// <summary>
/// Calculates current position based on velocity and acceleration
/// </summary>
/// <param name="time">Time elapsed (in seconds) since the last update of position</param>
/// <param name="position">New position</param>
public void UpdatePosition(double time, out Vector2 position, NPC flockingEntity = null)
{
UpdatePosition(time, flockingEntity);
position = this.position;
}
/// <summary>
/// Calculates current position based on velocity and acceleration
/// </summary>
/// <param name="time">Time elapsed (in seconds) since the last update of position</param>
public void UpdatePosition(double time, NPC flockingEntity = null)
{
// Steering
if (isSteering)
{
updatePositionSteering(time, flockingEntity);
}
else
{
updatePositionKinematic(time, flockingEntity);
}
// Calculates position
position += velocity * (float)time;
}
/// <summary>
/// Position update if kinematic
/// </summary>
/// <param name="time">Time since last update call</param>
private void updatePositionKinematic(double time, NPC flockingEntity = null)
{
// If stopping
if (isStopping)
{
// Stop
velocity = Vector2.Zero;
}
else
{
// Move at max speed in direction of the target
velocity = movementDirection;
velocity *= maxVelocity;
}
}
/// <summary>
/// Position update if steering
/// </summary>
/// <param name="time">Time since last update call</param>
private void updatePositionSteering(double time, NPC flockingEntity = null)
{
// If stopping
if (isStopping)
{
// Acceleration opposes last movement
acceleration = velocity * -friction;
// Capped by max acceleration
if (acceleration.Length() > maxAcceleration)
{
if(acceleration.LengthSquared() > 0)
acceleration.Normalize();
acceleration *= maxAcceleration;
}
// Update velocity
int signX = Math.Sign(velocity.X), signY = Math.Sign(velocity.Y);
velocity += acceleration * (float)time;
if (Math.Sign(velocity.X) != signX || Math.Abs(velocity.X) < 25)
{
velocity.X = 0;
}
if (Math.Sign(velocity.Y) != signY || Math.Abs(velocity.Y) < 25)
{
velocity.Y = 0;
}
if (flockingEntity != null && flockingEntity.flock != null)
{
float mult = 1;
if (maxVelocity == maxVelocityRun)
{
mult = maxVelocityRun / maxVelocityWalk;
}
velocity += flockingEntity.flock.computeAlignment(flockingEntity) * mult;
velocity += flockingEntity.flock.computeCohesion(flockingEntity) * mult;
velocity += flockingEntity.flock.computeSeparation(flockingEntity) * mult;
}
// Capped by max velocity
if (velocity.Length() > maxVelocity)
{
if(velocity.LengthSquared() > 0)
velocity.Normalize();
velocity *= maxVelocity;
}
}
else
{
// Accelerate fully in the direction of the target
acceleration = movementDirection;
acceleration *= maxAcceleration;
velocity += acceleration * (float)time;
if (flockingEntity != null && flockingEntity.flock != null)
{
float mult = 1;
if (maxVelocity == maxVelocityRun)
{
mult = maxVelocityRun / maxVelocityWalk;
}
velocity += flockingEntity.flock.computeAlignment(flockingEntity) * mult;
velocity += flockingEntity.flock.computeCohesion(flockingEntity) * mult;
velocity += flockingEntity.flock.computeSeparation(flockingEntity) * mult;
}
// Capped by max velocity
if (velocity.Length() > maxVelocity)
{
if (velocity.LengthSquared() > 0)
velocity.Normalize();
velocity *= maxVelocity;
}
}
}
/// <summary>
/// Sets the position to target
/// </summary>
/// <param name="targetPosition">Desired position</param>
public void SetTarget(Vector2 targetPosition, NPC flockingEnt = null)
{
this.targetPosition = targetPosition;
}
