// the following is for the main body of the A* algorithm
void ObtainPathbyVector(Vector2 Start, Vector2 End)
{
// the following line of code assigns the starting node from the grid to the nodes script
Node start = World.GetNodeFromWorld(Start);
// the code underneath assigns the end node from the grid to the nodes script
Node end = World.GetNodeFromWorld(End);
// this is to store all available points
List <Node> OpenPoints = new List <Node>();
HashSet <Node> ClosePoints = new HashSet <Node>();
// the following code adds the start point to the openlist
OpenPoints.Add(start);
// the loop below is executed until there are no open points left
while (OpenPoints.Count > 0)
{
// the following line of code is used to initialise a current position
Node CurrentPosition = OpenPoints[0];
// for loop to run through f.cost is compared to openpoints
for (int i = 0; i < OpenPoints.Count; i++)
{
// the following if statement checks whether the openpoints Fcos is smaller than the Fcos of the current position,
// or the openpoints Fcos is equal to the Fcos of the current position
if (OpenPoints[i].GetFcos < CurrentPosition.GetFcos || OpenPoints[i].GetFcos == CurrentPosition.GetFcos)
{
// the following if statement checks whether the Hcos of the openpoints is smaller than
// the Hcos of the current position
if (OpenPoints[i].Hcos < CurrentPosition.Hcos)
{
//so now the current position will equal to whatever the most efficient path is
CurrentPosition = OpenPoints[i];
}
}
}
// will store the most efficient path
ClosePoints.Add(CurrentPosition);
// removes the currentposition and moves on
OpenPoints.Remove(CurrentPosition);
// checks whether the current position is equal to the destination node
if (CurrentPosition == end)
{
PathGeneration(start, end);
//exits the loop
return;
}
foreach (Node sidenode in World.NeighbourOfPoint(CurrentPosition))
{
// the following code gets access to unwalkable areas
if (!sidenode.Walkable || ClosePoints.Contains(sidenode))// we say this because firstly we dont need to have access to unwalkable areas
//secondly there may be times where one of our side nodes has already been added to our closed list so we want to ignore those sidenodes
{
// the continues ignores nodes that have already been added to the closed list and moves on
continue;
}
// will calculate any distances
int MovementCost = CurrentPosition.Gcos + GetMoveCost(CurrentPosition, sidenode);
// checks if this sidenode is good or not
if (MovementCost < sidenode.Gcos || !OpenPoints.Contains(sidenode))
{
// makes the Gcos value of the side node equal to movementcost
sidenode.Gcos = MovementCost;
// is where the value of Hcos is calculated
sidenode.Hcos = GetMoveCost(sidenode, end);
// need this parent to back track our path
sidenode.Parent = CurrentPosition;
// checks whether the open points dont contain sidenode
if (!OpenPoints.Contains(sidenode))
{
// adds new points to the list
OpenPoints.Add(sidenode);
}
}
}
}
}
