private List <AStarNode> GetAdjacentWalkableNodes(AStarNode fromNode)
{
List <AStarNode> walkableNodes = new List <AStarNode>();
IEnumerable <Point> nextLocations = IsWalkableFrom(fromNode);
foreach (var location in nextLocations)
{
int x = location.X;
int y = location.Y;
// Stay within the grid's boundaries
if (x < 0 || x >= this.width || y < 0 || y >= this.height)
{
continue;
}
AStarNode node = this.nodes[x, y];
//float traversalCost = GetTraversal(fromNode.Location, location, Finish.Location); //1;
float traversalCost = GetTraversal(fromNode, node, Finish);
//node.ParentNode = fromNode;
if (node.Location == this.Finish.Location)
{
float gTemp = fromNode.G + traversalCost;
if (gTemp < node.G)
{
node.ParentNode = fromNode;
node.G = fromNode.G + traversalCost;
node.F = node.G + node.H;
walkableNodes.Add(node);
continue;
}
}
// Ignore non-walkable nodes
if (!node.IsWalkable)
{
continue;
}
// Ignore already-closed nodes
if (node.State == AStarNodeState.Closed)
{
continue;
}
/*
* {
* float gTemp = fromNode.G + traversalCost;
* if (gTemp < node.G)
* {
* node.ParentNode = fromNode;
* walkableNodes.Add(node);
* }
* }
*/
// Already-open nodes are only added to the list if their G-value is lower going via this route.
if (node.State == AStarNodeState.Open)// || node.State == AStarNodeState.Closed)
{
float gTemp = fromNode.G + traversalCost;
if (gTemp < node.G)
{
node.ParentNode = fromNode;
node.G = fromNode.G + traversalCost;
node.F = node.G + node.H;
walkableNodes.Add(node);
}
}
else
{
// If it's untested, set the parent and flag it as 'Open' for consideration
node.ParentNode = fromNode;
node.G = fromNode.G + traversalCost;
node.F = node.G + node.H;
node.State = AStarNodeState.Open;
walkableNodes.Add(node);
}
}
return(walkableNodes);
}
float GetTraversal(AStarNode from, AStarNode to, AStarNode destination)
{
// Prefer reading order, meaning U, L, R, D (N, W, E, S)
// This should also work for eight-direction or diagonals, though current intent is four cardinal directions.
float _ret = to.Cost;
/*
* float diffX = to.Location.X - from.Location.X;
* float diffY = to.Location.Y - from.Location.Y;
*
* if (diffX < 0 && diffY < 0) // up and left
* _ret -= 3f;
*
* else if (diffX == 0 && diffY < 0) // up
* _ret -= 2f;
*
* else if (diffX > 0 && diffY < 0) // up and right
* _ret += 1f;
*
* else if (diffX < 0 && diffY == 0) // left
* _ret += 0f;
*
* else if (diffX > 0 && diffY == 0) // right
* _ret += 1f;
*
* else if (diffX < 0 && diffY > 0) // down and left
* _ret += 2f;
*
* else if (diffX == 0 && diffY > 0) // down
* _ret += 3f;
*
* else if (diffX > 0 && diffY > 0) // down and right
* _ret += 4f;
*/
/*
* if (to.Location.Y < from.Location.Y) // Up / North
* {
* //_ret += 1.0f;
* _ret -= 0.5f;
* //_ret *= 1.0f; // No change in cost if up
* }
*
* else if (to.Location.Y == from.Location.Y) // Down / South
* {
* //_ret += 4.0f;
* _ret += 0f;
* //_ret *= 1.003f; // Even hight increase in cost if down
* }
*
* else if (to.Location.Y > from.Location.Y) // Down / South
* {
* //_ret += 4.0f;
* _ret += 0.5f;
* //_ret *= 1.003f; // Even hight increase in cost if down
* }
*
* if (to.Location.X < from.Location.X) // Left / West
* {
* //_ret += 2.0f;
* _ret -= 0.5f;
* //_ret *= 1.001f; // Slight increase in cost if left
* }
*
* else if (to.Location.X == from.Location.X) // Down / South
* {
* //_ret += 4.0f;
* _ret += 0f;
* //_ret *= 1.003f; // Even hight increase in cost if down
* }
*
* else if (to.Location.X > from.Location.X) // Right / East
* {
* //_ret += 3.0f;
* _ret += 0.5f;
* //_ret *= 1.002f; // Slightly higher increase in cost if right
* }
*/
return(_ret);
}