private List<Direction> _PathfinderAStar(Coords start, Coords endTopLeft, Coords endBottomRight, BitArray[] _passabilityMap, hFunction h)
{
// NOTE: Should later implemented a collision predictor mechanic to work in tandem
// with the path-finder to provide better agent behavior.
// NOTE: Consider returning the number of tiles scanned in case no path is found.
// This will alert a boxed-in creature of its predicament.
// NOTE: Introduce a flag for a straight-line initial check(for outdoors environmens and
// for when the goal is near).
Int32 rangeX = _passabilityMap.Length;
Int32 rangeY = _passabilityMap[0].Count;
NodeAStar?[,] nodeArray = new NodeAStar?[rangeX, rangeY];
NodeAStar startNode = new NodeAStar();
startNode.costSoFar = 0;
startNode.estimatedTotalCost = h(start);
nodeArray[start.X, start.Y] = startNode;
List<Coords> ListOpen = new List<Coords>();
ListOpen.Add(start);
while (ListOpen.Count > 0)
{
// I have to use this bool the way I've implemented the algo. Consider rewriting.
bool resortList = false;
Coords currentCoords = ListOpen.First();
// Check to see if goal is reached.
//if (currentCoords.Equals(endTopLeft))
if (StaticMathFunctions.CoordinateIsInBox(currentCoords, endTopLeft, endBottomRight))
{
break;
}
NodeAStar currentNode = nodeArray[currentCoords.X, currentCoords.Y].Value;
for (byte i = 0; i <= 3; ++i)
{
Direction currentDir = (Direction)(2 * i + 1);
Coords dirCoords = StaticMathFunctions.DirectionToCoords(currentDir);
Coords potential = currentCoords + dirCoords;
// check if move in dir is allowed
if (potential.X >= 0 && potential.X < rangeX && potential.Y >= 0 && potential.Y < rangeY // bounds check
&& _passabilityMap[potential.X][potential.Y]) // passability check
{
// Using the simplest cost function possible. Can be easily updated
// once tile walkability coefficients are added.
Coords newNodePosition = new Coords(CoordsType.General, currentCoords.X + dirCoords.X, currentCoords.Y + dirCoords.Y);
float accruedCost = currentNode.costSoFar + Constants.MovementCost[(byte)currentDir];
// Straight line correction
if (currentDir == nodeArray[currentCoords.X, currentCoords.Y].Value.connection)
{
accruedCost -= Constants.PathfinderStraightPathCorrection;
}
// Check to see if the node under examination is in the closed list.
//NodeAStar? oldNode = nodeArray[newNodePosition.X, newNodePosition.Y];
if (nodeArray[newNodePosition.X, newNodePosition.Y] != null)
{
// If node is in closed list, see if it needs updating.
if (nodeArray[newNodePosition.X, newNodePosition.Y].Value.costSoFar > accruedCost)
{
float expectedAdditionalCost =
nodeArray[newNodePosition.X, newNodePosition.Y].Value.estimatedTotalCost -
nodeArray[newNodePosition.X, newNodePosition.Y].Value.costSoFar;
NodeAStar nodeToAdd =
new NodeAStar(currentDir, accruedCost, accruedCost + expectedAdditionalCost);
nodeArray[newNodePosition.X, newNodePosition.Y] = nodeToAdd;
ListOpen.Add(newNodePosition);
resortList = true;
}
}
// Node is in open list. Process it.
else
{
float expectedAdditionalCost = h(newNodePosition);
NodeAStar nodeToAdd =
new NodeAStar(currentDir, accruedCost, accruedCost + expectedAdditionalCost);
nodeArray[newNodePosition.X, newNodePosition.Y] = nodeToAdd;
ListOpen.Add(newNodePosition);
resortList = true;
}
}
}
ListOpen.RemoveAt(0);
if (resortList)
{
ListOpen.Sort(
delegate(Coords c1, Coords c2)
{
float difference = nodeArray[c1.X, c1.Y].Value.estimatedTotalCost -
nodeArray[c2.X, c2.Y].Value.estimatedTotalCost;
Int32 returnValue = 0;
if (difference > 0)
{
returnValue = 1;
}
else if (difference < 0)
{
returnValue = -1;
}
return returnValue;
}
);
}
}
List<Direction> ListRoute = new List<Direction>();
// Return empty route if the open list is empty, i.e. there is no path to the target
// Ideally, the game logic should be fixed so that the search isn't even attempted
// if there is no path between the two points.
if (ListOpen.Count == 0)
{
return ListRoute;
}
Coords trackbackCoords = endTopLeft;
while (trackbackCoords != start)
{
Direction newDirection = nodeArray[trackbackCoords.X, trackbackCoords.Y].Value.connection;
ListRoute.Add(newDirection);
trackbackCoords = StaticMathFunctions.CoordsNeighboringInDirection(new Coords(CoordsType.Tile, trackbackCoords),
StaticMathFunctions.OppositeDirection(newDirection));
}
// Might be faster without reversing
//ListRoute.Reverse();
// We skip the reversal, so pick directions from the END of the list.
return ListRoute;
}
private List<Direction> _PathfinderAStar(Coords start, Coords endTopLeft, Coords endBottomRight, BitArray[] _passabilityMap, hFunction h)
{
// NOTE: Should later implemented a collision predictor mechanic to work in tandem
// with the path-finder to provide better agent behavior.
// NOTE: Consider returning the number of tiles scanned in case no path is found.
// This will alert a boxed-in creature of its predicament.
// NOTE: Introduce a flag for a straight-line initial check(for outdoors environmens and
// for when the goal is near).
Int32 rangeX = _passabilityMap.Length;
Int32 rangeY = _passabilityMap[0].Count;
NodeAStar?[,] nodeArray = new NodeAStar?[rangeX, rangeY];
NodeAStar startNode = new NodeAStar();
startNode.costSoFar = 0;
startNode.estimatedTotalCost = h(start);
nodeArray[start.X, start.Y] = startNode;
List<Coords> ListOpen = new List<Coords>();
ListOpen.Add(start);
while (ListOpen.Count > 0)
{
// I have to use this bool the way I've implemented the algo. Consider rewriting.
bool resortList = false;
Coords currentCoords = ListOpen.First();
// Check to see if goal is reached.
//if (currentCoords.Equals(endTopLeft))
if (StaticMathFunctions.CoordinateIsInBox(currentCoords, endTopLeft, endBottomRight))
{
break;
}
NodeAStar currentNode = nodeArray[currentCoords.X, currentCoords.Y].Value;
for (byte i = 0; i <= 5; ++i)
{
Direction currentDir = (Direction)(i);
//Coords dirCoords = StaticMathFunctions.DirectionToCoords(currentDir);
Coords potential = StaticMathFunctions.CoordsNeighboringInDirection(currentCoords, currentDir);
// check if move in dir is allowed
if (potential.X >= 0 && potential.X < rangeX && potential.Y >= 0 && potential.Y < rangeY // bounds check
&& _passabilityMap[potential.X][potential.Y]) // passability check
{
// Using the simplest cost function possible. Can be easily updated
// once tile walkability coefficients are added.
//Coords newNodePosition = new Coords(CoordsType.General, currentCoords.X + dirCoords.X, currentCoords.Y + dirCoords.Y);
Coords newNodePosition = potential;
float accruedCost = currentNode.costSoFar + 1;
// Straight line correction
if (currentDir == nodeArray[currentCoords.X, currentCoords.Y].Value.connection)
{
accruedCost -= Constants.PathfinderStraightPathCorrection;
}
// Check to see if the node under examination is in the closed list.
//NodeAStar? oldNode = nodeArray[newNodePosition.X, newNodePosition.Y];
if (nodeArray[newNodePosition.X, newNodePosition.Y] != null)
{
// If node is in closed list, see if it needs updating.
if (nodeArray[newNodePosition.X, newNodePosition.Y].Value.costSoFar > accruedCost)
{
float expectedAdditionalCost =
nodeArray[newNodePosition.X, newNodePosition.Y].Value.estimatedTotalCost -
nodeArray[newNodePosition.X, newNodePosition.Y].Value.costSoFar;
NodeAStar nodeToAdd =
new NodeAStar(currentDir, accruedCost, accruedCost + expectedAdditionalCost);
nodeArray[newNodePosition.X, newNodePosition.Y] = nodeToAdd;
ListOpen.Add(newNodePosition);
resortList = true;
}
}
// Node is in open list. Process it.
else
{
float expectedAdditionalCost = h(newNodePosition);
NodeAStar nodeToAdd =
new NodeAStar(currentDir, accruedCost, accruedCost + expectedAdditionalCost);
nodeArray[newNodePosition.X, newNodePosition.Y] = nodeToAdd;
ListOpen.Add(newNodePosition);
resortList = true;
}
}
}
ListOpen.RemoveAt(0);
if (resortList)
{
ListOpen.Sort(
delegate(Coords c1, Coords c2)
{
float difference = nodeArray[c1.X, c1.Y].Value.estimatedTotalCost -
nodeArray[c2.X, c2.Y].Value.estimatedTotalCost;
Int32 returnValue = 0;
if (difference > 0)
{
returnValue = 1;
}
else if (difference < 0)
{
returnValue = -1;
}
return returnValue;
}
);
}
}
List<Direction> ListRoute = new List<Direction>();
// Return empty route if the open list is empty, i.e. there is no path to the target
// Ideally, the game logic should be fixed so that the search isn't even attempted
// if there is no path between the two points.
if (ListOpen.Count == 0)
{
return ListRoute;
}
Coords trackbackCoords = endTopLeft;
while (trackbackCoords != start)
{
Direction newDirection = nodeArray[trackbackCoords.X, trackbackCoords.Y].Value.connection;
ListRoute.Add(newDirection);
trackbackCoords = StaticMathFunctions.CoordsNeighboringInDirection(new Coords(CoordsType.Tile, trackbackCoords),
StaticMathFunctions.OppositeDirection(newDirection));
}
// Might be faster without reversing
//ListRoute.Reverse();
// We skip the reversal, so pick directions from the END of the list.
return ListRoute;
}
