/**
* Determine the distance between two neighbor Cells
* as used by the AStar algorithm.
*
* @param cell1 any Cell
* @param cell2 any of cell1's neighbors
* @return Float - the distance between the two neighbors
*/
public float getDistanceBetween(AStarCell cell1, AStarCell cell2)
{
//if the cells are on top or next to each other, return 1
if (cell1.getX() == cell2.getX() || cell1.getY() == cell2.getY())
{
return(1);//*(mapHeight+mapWith);
}
else
{ //if they are diagonal to each other return diagonal distance: sqrt(1^2+1^2)
return(SQRT2); //*(mapHeight+mapWith);
}
}
public List <Point> calcShortestPath(int startX, int startY, int goalX, int goalY)
{
AStarCell startCell = map.getCell(startX, startY);
AStarCell goalCell = map.getCell(goalX, goalY);
//Check if the start cell is also an obstacle (if it is, it is impossible to find a path)
if (AStarCell.isObstacle(startCell))
{
UnityEngine.Debug.Log("start is null");
return(null);
}
//Check if the goal cell is also an obstacle (if it is, it is impossible to find a path there)
if (AStarCell.isObstacle(goalCell))
{
UnityEngine.Debug.Log("end is null");
return(null);
}
startCell.reset();
startCell.setDistanceFromStart(0);
closedList.Clear();
openList.Clear();
openList.Add(startCell);
//while we haven't reached the goal yet
while (openList.Count() != 0)
{
//get the first Cell from non-searched Cell list, sorted by lowest distance from our goal as guessed by our heuristic
AStarCell current = openList[0];
// check if our current Cell location is the goal Cell. If it is, we are done.
if (current.getX() == goalX && current.getY() == goalY)
{
return(reconstructPath(current));
}
//move current Cell to the closed (already searched) list
openList.Remove(current);
closedList.Add(current);
//go through all the current Cells neighbors and calculate if one should be our next step
foreach (AStarCell neighbor in map.getNeighborList(current))
{
bool neighborIsBetter;
//if we have already searched this Cell, don't bother and continue to the next one
if (closedList.Contains(neighbor))
{
continue;
}
// calculate how long the path is if we choose this neighbor as the next step in the path
float neighborDistanceFromStart = (current.getDistanceFromStart() + AStarMap.getDistanceBetween(current, neighbor));
//add neighbor to the open list if it is not there
if (!openList.Contains(neighbor))
{
neighbor.reset();
openList.Add(neighbor);
neighborIsBetter = true;
//if neighbor is closer to start it could also be better
}
else if (neighborDistanceFromStart < current.getDistanceFromStart())
{
neighborIsBetter = true;
}
else
{
neighborIsBetter = false;
}
// set neighbors parameters if it is better
if (neighborIsBetter)
{
neighbor.setPreviousCell(current);
neighbor.setDistanceFromStart(neighborDistanceFromStart);
neighbor.setHeuristicDistanceFromGoal(heuristic.getEstimatedDistanceToGoal(
neighbor.getX(), neighbor.getY(), goalCell.getX(), goalCell.getY()));
// csharp List.Sort use QuickSort, which is unstable,
// but in java implement ArrayList.sort use MergeSort, which is stable,
// so here use MergeSort to generate the same result as in java implement
MergeSortClass.MergeSort(openList);
}
}
}
UnityEngine.Debug.Log("path is null");
return(null);
}
public List <AStarCell> getNeighborList(AStarCell cell)
{
List <AStarCell> neighborList = new List <AStarCell>();
bool downWalkable = false;
if (cell.getY() > 0)
{// down
AStarCell neighbor = getCell(cell.getX(), (cell.getY() - 1));
if (!AStarCell.isObstacle(neighbor))
{
neighborList.Add(neighbor);
downWalkable = true;
}
}
bool rightWalkable = false;
if (cell.getX() < (widthInCells - 1))
{// right
AStarCell neighbor = getCell(cell.getX() + 1, cell.getY());
if (!AStarCell.isObstacle(neighbor))
{
neighborList.Add(neighbor);
rightWalkable = true;
}
}
bool upWalkable = false;
if (cell.getY() < (heightInCells - 1))
{// up
AStarCell neighbor = getCell(cell.getX(), cell.getY() + 1);
if (!AStarCell.isObstacle(neighbor))
{
neighborList.Add(neighbor);
upWalkable = true;
}
}
bool leftWalkable = false;
if (cell.getX() > 0)
{// left
AStarCell neighbor = getCell(cell.getX() - 1, cell.getY());
if (!AStarCell.isObstacle(neighbor))
{
neighborList.Add(neighbor);
leftWalkable = true;
}
}
if (downWalkable || rightWalkable)
{
if (cell.getX() < (widthInCells - 1) && cell.getY() > 0)
{// down right
AStarCell neighbor = getCell(cell.getX() + 1, cell.getY() - 1);
if (!AStarCell.isObstacle(neighbor))
{
neighborList.Add(neighbor);
}
}
}
if (upWalkable || rightWalkable)
{
if (cell.getX() < (widthInCells - 1) && cell.getY() < (heightInCells - 1))
{ // up right
AStarCell neighbor = getCell(cell.getX() + 1, cell.getY() + 1);
if (!AStarCell.isObstacle(neighbor))
{
neighborList.Add(neighbor);
}
}
}
if (upWalkable || leftWalkable)
{
if (cell.getX() > 0 && cell.getY() < (heightInCells - 1))
{// up left
AStarCell neighbor = getCell(cell.getX() - 1, cell.getY() + 1);
if (!AStarCell.isObstacle(neighbor))
{
neighborList.Add(neighbor);
}
}
}
if (downWalkable || leftWalkable)
{
if (cell.getX() > 0 && cell.getY() > 0)
{// down left
AStarCell neighbor = getCell(cell.getX() - 1, cell.getY() - 1);
if (!AStarCell.isObstacle(neighbor))
{
neighborList.Add(neighbor);
}
}
}
return(neighborList);
}