//this method calculates all a target's neighbors and stores them in
//the neighbor vector. After you have called this method use the begin,
//next, and end methods to iterate through the vector.
public IEnumerable <T> CalculateNeighbors(Vector2D searcherPos, double QueryRadius)
{
//create the query box that is the bounding box of the target's query
//area
var topLeft = searcherPos - new Vector2D(QueryRadius, QueryRadius);
var bottomRight = searcherPos + new Vector2D(QueryRadius, QueryRadius);
var queryBox = new InvertedBox(topLeft, bottomRight);
//iterate through each cell and test to see if its bounding box overlaps
//with the query box. If it does and it also contains entities then
//make further proximity tests.
var i = 0;
while (i < _cells.Count)
{
var members = _cells[i].Members.Values.ToList();
//test to see if this cell contains members and if it overlaps the
//query box
if (_cells[i].BoundingBox.Overlap(queryBox) && members.Any())
{
int j = 0;
//add any entities found within query radius to the neighbor list
while (j < members.Count)
{
var target = members[j];
if (target != null && (target.Pos - searcherPos).LengthSquared() < QueryRadius * QueryRadius)
{
yield return(target);
}
j++;
}
}
i++;
}
}
public bool Overlap(InvertedBox box)
{
return(this.Left < box.Right && this.Right > box.Left &&
this.Top < box.Bottom && this.Bottom > box.Top);
}
public Cell(Vector2D topleft, Vector2D botright)
{
Members = new ConcurrentDictionary <int, T>();
BoundingBox = new InvertedBox(topleft, botright);
}
