/// <summary>
/// Internal function that implements the path-finding algorithm.
/// </summary>
/// <param name="pGrid">Grid to search.</param>
/// <param name="startPos">Starting position.</param>
/// <param name="targetPos">Ending position.</param>
/// <param name="distance">The type of distance, Euclidean or Manhattan.</param>
/// <param name="ignorePrices">If true, will ignore tile price (how much it "cost" to walk on).</param>
/// <returns>List of grid nodes that represent the path to walk.</returns>
private static List <Node> _ImpFindPath(PGrid pGrid, PPoint startPos, PPoint targetPos, DistanceType distance = DistanceType.Euclidean, bool ignorePrices = false)
{
Node startNode = pGrid.nodes[startPos.x, startPos.y];
Node targetNode = pGrid.nodes[targetPos.x, targetPos.y];
List <Node> openSet = new List <Node>();
HashSet <Node> closedSet = new HashSet <Node>();
openSet.Add(startNode);
while (openSet.Count > 0)
{
Node currentNode = openSet[0];
for (int i = 1; i < openSet.Count; i++)
{
if (openSet[i].fCost < currentNode.fCost || openSet[i].fCost == currentNode.fCost && openSet[i].hCost < currentNode.hCost)
{
currentNode = openSet[i];
}
}
openSet.Remove(currentNode);
closedSet.Add(currentNode);
if (currentNode == targetNode)
{
return(RetracePath(pGrid, startNode, targetNode));
}
foreach (Node neighbour in pGrid.GetNeighbours(currentNode, distance))
{
if (!neighbour.walkable || closedSet.Contains(neighbour))
{
continue;
}
int newMovementCostToNeighbour = currentNode.gCost + GetDistance(currentNode, neighbour) * (ignorePrices ? 1 : (int)(10.0f * neighbour.price));
if (newMovementCostToNeighbour < neighbour.gCost || !openSet.Contains(neighbour))
{
neighbour.gCost = newMovementCostToNeighbour;
neighbour.hCost = GetDistance(neighbour, targetNode);
neighbour.parent = currentNode;
if (!openSet.Contains(neighbour))
{
openSet.Add(neighbour);
}
}
}
}
return(null);
}
/// <summary>
/// Retrace path between two points.
/// </summary>
/// <param name="pGrid">Grid to work on.</param>
/// <param name="startNode">Starting node.</param>
/// <param name="endNode">Ending (target) node.</param>
/// <returns>Retraced path between nodes.</returns>
private static List <Node> RetracePath(PGrid pGrid, Node startNode, Node endNode)
{
List <Node> path = new List <Node>();
Node currentNode = endNode;
while (currentNode != startNode)
{
path.Add(currentNode);
currentNode = currentNode.parent;
}
path.Reverse();
return(path);
}
/// <summary>
/// Find a path between two points.
/// </summary>
/// <param name="pGrid">Grid to search.</param>
/// <param name="startPos">Starting position.</param>
/// <param name="targetPos">Ending position.</param>
/// <param name="distance">The type of distance, Euclidean or Manhattan.</param>
/// <param name="ignorePrices">If true, will ignore tile price (how much it "cost" to walk on).</param>
/// <returns>List of points that represent the path to walk.</returns>
public static List <PPoint> FindPath(PGrid pGrid, PPoint startPos, PPoint targetPos, DistanceType distance = DistanceType.Euclidean, bool ignorePrices = false)
{
// find path
List <Node> nodes_path = _ImpFindPath(pGrid, startPos, targetPos, distance, ignorePrices);
// convert to a list of points and return
List <PPoint> ret = new List <PPoint>();
if (nodes_path != null)
{
foreach (Node node in nodes_path)
{
ret.Add(new PPoint(node.gridX, node.gridY));
}
}
return(ret);
}
