/// <summary>
/// Initializes a discrete grid using the information provided.
/// </summary>
/// <param name="startPoint">The point to start the route at</param>
/// <param name="endPoint">The point to end the route at</param>
/// <param name="field">The field that needs to be discretised</param>
/// <param name="gridSize">The size of the grid to be palced placed over <paramref name="field"/></param>
/// <param name="movingObject">The object that will be moving.</param>
/// <returns>A GridSquare array, initialized to represent <paramref name="field"/>.</returns>
///
/// Produces a GridSquare array that is set up for use by <see cref="FindPath"/>.
///
/// Uses the ObjectClearance and <paramref name="movingObject" />'s <see cref="IPositionedObject.Size"/> property to determine the
/// apparent size of opponents, and marks the squares that contain them as <see cref="SquareType.Obstacle"/>.
///
/// Marks the square that contains <paramref name="endPoint" /> as <see cref="SquareType.Destination"/>.
///
/// Marks the square that contains <paramref name="startPoint" /> as <see cref="SquareType.Origin"/>.
///
/// Works in parallel as far as possible, using the Microsoft Task Parallel Library (http://msdn.microsoft.com/en-us/library/dd460717.aspx).
protected GridSquare[] InitGrid(PointF startPoint, PointF endPoint, Field field, Size gridSize, IPositionedObject movingObject)
{
var playersize = (movingObject.Size + new Size(ObjectClearance, ObjectClearance)).Scale(Resolution).Scale(2.0f).Ceiling();
var clearance = Math.Max(playersize.Width, playersize.Height); // The amount to increase an obstacle's size by to allow for the player's size
var grid = new GridSquare[gridSize.Height * gridSize.Width];
// Initialize the grid
Parallel.For(0, grid.Length, i => {
grid[i] = new GridSquare
{
Location = PointExtensions.FromIndex(i, gridSize.Width)
};
});
Parallel.ForEach(from p in field.Players where p.Team == Team.Opposition select p, player =>
{
var centerGridPoint = player.Position.Scale(Resolution).Floor();
var minX = Math.Max(0, centerGridPoint.X - playersize.Width - clearance);
var maxX = Math.Min(centerGridPoint.X + playersize.Width + clearance, gridSize.Width);
var minY = Math.Max(0, centerGridPoint.Y - playersize.Height - clearance);
var maxY = Math.Min(centerGridPoint.Y + playersize.Height + clearance, gridSize.Height);
for (var i = minX; i < maxX; i++)
{
for (var j = minY; j < maxY; j++)
{
if (i < 0 || j < 0)
{
continue;
}
var gridPoint = new Point(i, j);
grid[gridPoint.ToIndex(gridSize.Width)].Type = SquareType.Obstacle;
}
}
});
var gridEndPoint = endPoint.Scale(Resolution).Floor();
grid[gridEndPoint.ToIndex(gridSize.Width)].Type = SquareType.Destination;
var gridStartPoint = startPoint.Scale(Resolution).Floor();
grid[gridStartPoint.ToIndex(gridSize.Width)].Type = SquareType.Origin;
return(grid);
}
/// <summary>
/// Calculates the heuristic score for the given square.
/// </summary>
/// <param name="square">The square to calculate the heuristic for </param>
/// <param name="endPoint">The current point to aim for </param>
/// <returns>
/// \f$+\infty\f$ if the square is an obstacle
///
/// CalculateLength(square.Location, endPoint) otherwise
/// </returns>
protected float CalculateHeuristic(GridSquare square, PointF endPoint)
{
return(square.Type == SquareType.Obstacle ? float.PositiveInfinity : CalculateLength(square.Location, endPoint));
}
/// <summary>
/// Reconstructs a path from the given cameFrom information.
/// </summary>
/// <param name="cameFrom">The list of 'came from' details produced by the A* algorithm</param>
/// <param name="currentSquare">The current square to examine</param>
/// <returns>The shortest Route to the destination</returns>
///
/// A recursive algorithm that reconstructs the path that has been produced by the A* algorithm
protected Route ReconstructPath(Dictionary <GridSquare, GridSquare> cameFrom, GridSquare currentSquare)
{
if (cameFrom.ContainsKey(currentSquare))
{
var path = ReconstructPath(cameFrom, cameFrom[currentSquare]);
path.Path.Add(new LineSegment(cameFrom[currentSquare].Location, currentSquare.Location));
return(path);
}
return(new Route());
}
