/* Alignment
* Align the heading of an agent based on those of its neighbors. The
* force is calculated by generating an average heading vector. We then
* subtract the agent's heading to get the steering force for the agent.
*
* We assume that neighbors represents all of the visible neighbors of the
* provided agent.
*/
private static Vector2 ComputeAlignment(Agent agent, List<Flockable> neighbors)
{
// A running sum of the given agent's neighbors headings.
Vector2 headingSum = new Vector2();
int divisor = 0;
Vector2 weightedHeading;
// For each of the given agents neighbors...
foreach (Flockable otherAgent in neighbors)
{
// Ensure that our agent was not counted among its neighbors.
if (agent.Equals(otherAgent) == false)
{
// Add our neighbors heading to our running sum
weightedHeading = Vector2.Multiply(otherAgent.getHeading(), otherAgent.getFlockingWeight());
headingSum = Vector2.Add(headingSum, weightedHeading);
// Necessary as we allow our given boid to be included in the neighbors.
divisor += otherAgent.getFlockingWeight();
}
}
// The average of the neighbor headings.
// Zero vector in the event that provided agent has no neighbors.
Vector2 averageHeading = new Vector2();
if (divisor > 0) // Avoid divide by zero erros.
{
// Basic math.
averageHeading = Vector2.Divide(headingSum, (float) divisor);
// Subtract the provided agent's heading to produce the steering force.
// If this is puzzling the most effective way to think about this is to draw a
// picture of the current heading and the average heading.
averageHeading = Vector2.Subtract(averageHeading, agent.getHeading());
}
// Return steering force necessary to achieve alignment with peers.
return averageHeading;
}
