Replanning and flow fields

using RecursiveAI.OnePath;
 
var yard = new Grid(16, 8);
using GridReplanner replanner = yard.CreateReplanner(new Cell(0, 0), new Cell(15, 0));
GridPath first = replanner.Replan();
Console.WriteLine($"open yard:   cost {first.Cost:F4}, {first.Cells.Length} cells");
 
yard.SetRect(7, 0, 1, 7, AreaCosts.Wall);   // a wall appears, open only at the bottom row
GridPath detour = replanner.Replan();
Console.WriteLine($"after wall:  cost {detour.Cost:F4}, {detour.Cells.Length} cells");
 
replanner.MoveStart(new Cell(4, 5));        // the unit has moved along
GridPath onward = replanner.Replan();
Console.WriteLine($"moved start: cost {onward.Cost:F4}, {onward.Cells.Length} cells");
 
// One flow field serves every unit heading for the same goal.
using GridFlowField toGoal = yard.CreateFlowField(new Cell(15, 0));
foreach (var unit in new[] { new Cell(0, 0), new Cell(3, 6), new Cell(12, 2) })
{
    toGoal.TryGetNext(unit, out Cell next);
    Console.WriteLine($"unit at ({unit.X},{unit.Y}): cost to goal {toGoal.GetCost(unit):F4}, next step ({next.X},{next.Y})");
}

open yard:   cost 15.0000, 16 cells
after wall:  cost 21.3848, 17 cells
moved start: cost 14.7279, 12 cells
unit at (0,0): cost to goal 21.3848, next step (0,1)
unit at (3,6): cost to goal 15.3137, next step (4,6)
unit at (12,2): cost to goal 3.8284, next step (13,1)