public IEnumerable <PathfindCell> GetGlobalPath(Vector2 globalFrom, Vector2 globalTo)
{
var fromId = _astar.GetClosestPoint(globalFrom / TILE_SIZE);
var toId = _astar.GetClosestPoint(globalTo / TILE_SIZE);
var idPath = _astar.GetIdPath(fromId, toId);
var offset = new Vector2(TILE_SIZE / 2f, TILE_SIZE);
return(idPath.Select(x => new PathfindCell(x, _astar.GetPointWeightScale(x), _astar.GetPointPosition(x) * TILE_SIZE + offset)));
}
//Calculates the Minimum Spanning Tree (MST) for given points and returns an `AStar2D` graph using Prim's algorithm.
// https://en.wikipedia.org/wiki/Prim%27s_algorithm
// https://en.wikipedia.org/wiki/Minimum_spanning_tree
public static AStar2D MST(List <Vector2> pointsList)
{
var result = new AStar2D();
var firstPoint = pointsList.LastOrDefault();
//Start from an arbitrary point in the list of points
result.AddPoint(result.GetAvailablePointId(), firstPoint);
pointsList.Remove(firstPoint);
//Loop through all points, erasing them as we connect them.
while (pointsList.Any())
{
var currentPosition = Vector2.Zero;
var minPosition = Vector2.Zero;
var minDistance = float.PositiveInfinity;
foreach (int point1Id in result.GetPoints())
{
//Compare each point added to the Astar2D graph to each remaining point to find the closest one
var point1Position = result.GetPointPosition(point1Id);
foreach (var point2Position in pointsList)
{
var distance = point1Position.DistanceTo(point2Position);
if (minDistance > distance)
{
//We use the variables to store the coordinates of the closest point.
//We have to loop over all points to ensure it's the closest.
currentPosition = point1Position;
minPosition = point2Position;
minDistance = distance;
}
}
}
//Connect the point closest to the "current position" with our new point
var pointId = result.GetAvailablePointId();
result.AddPoint(pointId, minPosition);
result.ConnectPoints(result.GetClosestPoint(currentPosition), pointId);
pointsList.Remove(minPosition);
}
return(result);
}
