// Splits our level up into a grid of nodes.
private void InitializeSearchNodes(PlaygroundScene map)
{
searchNodes = new SearchNode[levelWidth, levelHeight];
// creates a search node for each of the tiles in our map
for (int x = 0; x < levelWidth; x++)
{
for (int y = 0; y < levelHeight; y++)
{
//Create a search node to represent this tile.
SearchNode node = new SearchNode();
node.Position = new Point(x, y);
// Player can only walk on grass tiles.
//node.Walkable = map.movedata[y, x] == 0;
node.Walkable = map.GetIndex(x, y) == 0;
// only store nodes that can be walked on.
if (node.Walkable == true)
{
node.Neighbors = new SearchNode[4];
searchNodes[x, y] = node;
}
}
}
// for each of the search nodes connects it to each of its neighbours.
for (int x = 0; x < levelWidth; x++)
{
for (int y = 0; y < levelHeight; y++)
{
SearchNode node = searchNodes[x, y];
//only want to look at the nodes that are walkable
if (node == null || node.Walkable == false)
{
continue;
}
// An array of all of the possible neighbors this node could have.
Point[] neighbors = new Point[]
{
new Point (x, y - 1), // The node above the current node
new Point (x, y + 1), // The node below the current node.
new Point (x - 1, y), // The node left of the current node.
new Point (x + 1, y), // The node right of the current node
};
// loop through each of the possible neighbors
for (int i = 0; i < neighbors.Length; i++)
{
Point position = neighbors[i];
// Check if neighbor is part of the level.
if (position.X < 0 || position.X > levelWidth - 1 ||
position.Y < 0 || position.Y > levelHeight - 1)
{
continue;
}
SearchNode neighbor = searchNodes[position.X, position.Y];
// Keeps a reference to the nodes that can be walked on.
if (neighbor == null || neighbor.Walkable == false)
{
continue;
}
// Store a reference to the neighbor.
node.Neighbors[i] = neighbor;
}
}
}
}
// Splits our level up into a grid of nodes.
private void InitializeSearchNodes(PlaygroundScene map)
{
searchNodes = new SearchNode[levelWidth, levelHeight];
// creates a search node for each of the tiles in our map
for (int x = 0; x < levelWidth; x++)
{
for (int y = 0; y < levelHeight; y++)
{
//Create a search node to represent this tile.
SearchNode node = new SearchNode();
node.Position = new Point(x, y);
// Player can only walk on grass tiles.
//node.Walkable = map.movedata[y, x] == 0;
node.Walkable = map.GetIndex(x, y) == 0;
// only store nodes that can be walked on.
if (node.Walkable == true)
{
node.Neighbors = new SearchNode[4];
searchNodes[x, y] = node;
}
}
}
// for each of the search nodes connects it to each of its neighbours.
for (int x = 0; x < levelWidth; x++)
{
for (int y = 0; y < levelHeight; y++)
{
SearchNode node = searchNodes[x, y];
//only want to look at the nodes that are walkable
if (node == null || node.Walkable == false)
{
continue;
}
// An array of all of the possible neighbors this node could have.
Point[] neighbors = new Point[]
{
new Point(x, y - 1), // The node above the current node
new Point(x, y + 1), // The node below the current node.
new Point(x - 1, y), // The node left of the current node.
new Point(x + 1, y), // The node right of the current node
};
// loop through each of the possible neighbors
for (int i = 0; i < neighbors.Length; i++)
{
Point position = neighbors[i];
// Check if neighbor is part of the level.
if (position.X < 0 || position.X > levelWidth - 1 ||
position.Y < 0 || position.Y > levelHeight - 1)
{
continue;
}
SearchNode neighbor = searchNodes[position.X, position.Y];
// Keeps a reference to the nodes that can be walked on.
if (neighbor == null || neighbor.Walkable == false)
{
continue;
}
// Store a reference to the neighbor.
node.Neighbors[i] = neighbor;
}
}
}
}
// Use the parent field of the search nodes to trace a path from the end node to the start node.
private List<Vector2> FindFinalPath(SearchNode startNode, SearchNode endNode)
{
closedList.Add(endNode);
SearchNode parentTile = endNode.Parent;
// Trace back through the nodes using the parent fieldsto find the best path.
while (parentTile != startNode)
{
closedList.Add(parentTile);
parentTile = parentTile.Parent;
}
List<Vector2> finalPath = new List<Vector2>();
// Reverse the path and transform into world space.
for (int i = closedList.Count - 1; i >= 0; i--)
{
finalPath.Add(new Vector2(closedList[i].Position.X * 48,
closedList[i].Position.Y * 48));
}
return finalPath;
}
// Finds the optimal path from one point to another.
public List <Vector2> FindPath(Point startPoint, Point endPoint)
{
// Only try to find a path if the start and end points are different.
if (startPoint == endPoint)
{
return(new List <Vector2>());
}
//clear previous nodes
ResetSearchNodes();
//Store references to the start and end nodes for convenience.
SearchNode startNode = searchNodes[startPoint.X, startPoint.Y];
SearchNode endNode = searchNodes[endPoint.X, endPoint.Y];
//Find estimated distance
startNode.InOpenList = true;
startNode.DistanceToGoal = Heuristic(startPoint, endPoint);
startNode.DistanceTraveled = 0;
openList.Add(startNode);
//loop through all the open nodes
while (openList.Count > 0)
{
//Find the smallest/best value
SearchNode currentNode = FindBestNode();
//if no path can be found then terminate
if (currentNode == null)
{
break;
}
//return the path
if (currentNode == endNode)
{
// Trace our path back to the start.
return(FindFinalPath(startNode, endNode));
}
//check the nodes neighbors
for (int i = 0; i < currentNode.Neighbors.Length; i++)
{
SearchNode neighbor = currentNode.Neighbors[i];
//checks it neighbor is walkable
if (neighbor == null || neighbor.Walkable == false)
{
continue;
}
//get new value for neighbor node
float distanceTraveled = currentNode.DistanceTraveled + 1;
// An estimate of the distance from this node to the end node.
float heuristic = Heuristic(neighbor.Position, endPoint);
// If the neighbouring node is not in either the Open List or the Closed List :
if (neighbor.InOpenList == false && neighbor.InClosedList == false)
{
// (1) Set the neighbouring node’s G value to the G value we just calculated.
neighbor.DistanceTraveled = distanceTraveled;
// (2) Set the neighbouring node’s F value to the new G value + the estimated
// distance between the neighbouring node and goal node.
neighbor.DistanceToGoal = distanceTraveled + heuristic;
// (3) Set the neighbouring node’s Parent property to point at the Active Node.
neighbor.Parent = currentNode;
// (4) Add the neighbouring node to the Open List.
neighbor.InOpenList = true;
openList.Add(neighbor);
}
// Else if the neighbouring node is in either the Open List or the Closed List :
else if (neighbor.InOpenList || neighbor.InClosedList)
{
if (neighbor.DistanceTraveled > distanceTraveled)
{
neighbor.DistanceTraveled = distanceTraveled;
neighbor.DistanceToGoal = distanceTraveled + heuristic;
neighbor.Parent = currentNode;
}
}
}
// Remove the Active Node from the Open List and add it to the Closed List
openList.Remove(currentNode);
currentNode.InClosedList = true;
}
// No path could be found.
return(new List <Vector2>());
}
