A* Pathfinding Project  3.8
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FloodPath Class Reference

Floods the area completely for easy computation of any path to a single point. More...

Detailed Description

Floods the area completely for easy computation of any path to a single point.

This path is a bit special, because it does not do anything useful by itself. What it does is that it calculates paths to all nodes it can reach, it floods the graph. This data will remain stored in the path. Then you can call a FloodPathTracer path, that path will trace the path from it's starting point all the way to where this path started flooding and thus generating a path extremely quickly.
It is very useful in for example TD (Tower Defence) games where all your AIs will walk to the same point, but from different places, and you do not update the graph or change the target point very often, what changes is their positions and new AIs spawn all the time (which makes it hard to use the MultiTargetPath).

With this path type, it can all be handled easily.

  • At start, you simply start ONE FloodPath and save the reference (it will be needed later).
  • Then when a unit is spawned or needs its path recalculated, start a FloodPathTracer path from it's position. It will then find the shortest path to the point specified when you called the FloodPath extremely quickly.
  • If you update the graph (for example place a tower in a TD game) or need to change the target point, you simply call a new FloodPath (and store it's reference).
From 3.2 and up, path traversal data is now stored in the path class. So you can now use other path types in parallel with this one.

Here follows some example code of the above list of steps:

public static FloodPath fpath;
public void Start () {
fpath = FloodPath.Construct (someTargetPosition, null);

When searching for a new path to someTargetPosition from let's say transform.position, you do

FloodPathTracer fpathTrace = FloodPathTracer.Construct (transform.position,fpath,null);
seeker.StartPath (fpathTrace,OnPathComplete);

Where OnPathComplete is your callback function.
Another thing to note is that if you are using NNConstraints on the FloodPathTracer, they must always inherit from Pathfinding.PathIDConstraint.
The easiest is to just modify the instance of PathIDConstraint which is created as the default one.

A* Pro Feature:
This is an A* Pathfinding Project Pro feature only. This function/class/variable might not exist in the Free version of the A* Pathfinding Project or the functionality might be limited
The Pro version can be bought here

Public Member Functions

 FloodPath ()
 Default constructor.
override void CalculateStep (long targetTick)
 Opens nodes until there are none left to search (or until the max time limit has been exceeded)
GraphNode GetParent (GraphNode node)
bool HasPathTo (GraphNode node)
override void Initialize ()
 Initializes the path.
override void Prepare ()
 Called before the path is started.
override void Reset ()
 Reset all values to their default values.
- Public Member Functions inherited from Path
void AdvanceState (PathState s)
 Threadsafe increment of the state.
uint CalculateHScore (GraphNode node)
 Estimated cost from the specified node to the target.
bool CanTraverse (GraphNode node)
 Returns if the node can be traversed.
void Claim (System.Object o)
 Claim this path (pooling).
virtual void Cleanup ()
 Always called after the path has been calculated.
virtual string DebugString (PathLog logMode)
 Returns a string with information about it.
void Error ()
 Aborts the path because of an error.
void ForceLogError (string msg)
 Logs an error and calls Error().
virtual uint GetConnectionSpecialCost (GraphNode a, GraphNode b, uint currentCost)
 May be called by graph nodes to get a special cost for some connections.
Int3 GetHTarget ()
PathState GetState ()
 Returns the state of the path in the pathfinding pipeline.
uint GetTagPenalty (int tag)
 Returns penalty for the given tag.
float GetTotalLength ()
 Total Length of the path.
uint GetTraversalCost (GraphNode node)
bool IsDone ()
 Returns if this path is done calculating.
void Log (string msg)
 Appends a message to the errorLog.
void LogError (string msg)
 Appends msg to errorLog and logs msg to the console.
virtual void OnEnterPool ()
 Called when the path enters the pool.
void Release (System.Object o, bool silent=false)
 Releases a path claim (pooling).
void ReleaseSilent (System.Object o)
 Releases the path silently (pooling).
virtual void ReturnPath ()
 Calls callback to return the calculated path.
IEnumerator WaitForPath ()
 Waits until this path has been calculated and returned.

Static Public Member Functions

static FloodPath Construct (Vector3 start, OnPathDelegate callback=null)
static FloodPath Construct (GraphNode start, OnPathDelegate callback=null)

Public Attributes

Vector3 originalStartPoint
bool saveParents = true
 If false, will not save any information.
GraphNode startNode
Vector3 startPoint
- Public Attributes inherited from Path
OnPathDelegate callback
 Callback to call when the path is complete.
float duration
 The duration of this path in ms.
int enabledTags = -1
 Which graph tags are traversable.
Heuristic heuristic
 Determines which heuristic to use.
float heuristicScale = 1F
 Scale of the heuristic values.
OnPathDelegate immediateCallback
 Immediate callback to call when the path is complete.
NNConstraint nnConstraint = PathNNConstraint.Default
 Constraint for how to search for nodes.
List< GraphNodepath
 Holds the path as a Node array.
int searchedNodes
 Number of nodes this path has searched.
int searchIterations
 The number of frames/iterations this path has executed.
List< Vector3 > vectorPath
 Holds the (perhaps post processed) path as a Vector3 list.

Protected Member Functions

void Setup (Vector3 start, OnPathDelegate callback)
void Setup (GraphNode start, OnPathDelegate callback)
- Protected Member Functions inherited from Path
void DebugStringPrefix (PathLog logMode, System.Text.StringBuilder text)
 Writes text shared for all overrides of DebugString to the string builder.
void DebugStringSuffix (PathLog logMode, System.Text.StringBuilder text)
 Writes text shared for all overrides of DebugString to the string builder.
bool HasExceededTime (int searchedNodes, long targetTime)
virtual void Trace (PathNode from)
 Traces the calculated path from the end node to the start.

Protected Attributes

Dictionary< GraphNode, GraphNodeparents
- Protected Attributes inherited from Path
PathNode currentR
 The node currently being processed.
bool hasBeenReset
 True if the Reset function has been called.
Int3 hTarget
 Target to use for H score calculations.
GraphNode hTargetNode
 Target to use for H score calculation.
int[] internalTagPenalties
 The tag penalties that are actually used.
int[] manualTagPenalties
 Tag penalties set by other scripts.
float maxFrameTime
 The max number of milliseconds per iteration (frame, in case of non-multithreading)


override bool FloodingPath [get]
- Properties inherited from Path
System.DateTime callTime [get, set]
 When the call was made to start the pathfinding for this path.
PathCompleteState CompleteState [get, set]
 Current state of the path.
bool error [get]
 If the path failed, this is true.
string errorLog [get]
 Log messages with info about eventual errors.
virtual bool FloodingPath [get]
 True for paths that want to search all nodes and not jump over nodes as optimizations.
PathHandler pathHandler [get, set]
 Data for the thread calculating this path.
ushort pathID [get, set]
 ID of this path.
bool recycled [get, set]
 True if the path is currently recycled (i.e in the path pool).
int[] tagPenalties [get, set]
 Penalties for each tag.

Additional Inherited Members

- Package Functions inherited from Path
void PrepareBase (PathHandler pathHandler)
 Prepares low level path variables for calculation.
- Package Attributes inherited from Path
Path next
 Internal linked list implementation.
bool pooled
 True if the path is currently pooled.

Constructor & Destructor Documentation

FloodPath ( )

Default constructor.

Do not use this. Instead use the static Construct method which can handle path pooling.

Member Function Documentation

override void CalculateStep ( long  targetTick)

Opens nodes until there are none left to search (or until the max time limit has been exceeded)

Implements Path.

static FloodPath Construct ( Vector3  start,
OnPathDelegate  callback = null 
static FloodPath Construct ( GraphNode  start,
OnPathDelegate  callback = null 
GraphNode GetParent ( GraphNode  node)
bool HasPathTo ( GraphNode  node)
override void Initialize ( )

Initializes the path.

Sets up the open list and adds the first node to it

Implements Path.

override void Prepare ( )

Called before the path is started.

Called right before Initialize

Implements Path.

override void Reset ( )

Reset all values to their default values.

All inheriting path types (e.g ConstantPath, RandomPath, etc.) which declare their own variables need to override this function, resetting ALL their variables to enable recycling of paths. If this is not done, trying to use that path type for pooling might result in weird behaviour. The best way is to reset to default values the variables declared in the extended path type and then call this base function in inheriting types with base.Reset ().
This function should not be called manually.

Reimplemented from Path.

void Setup ( Vector3  start,
OnPathDelegate  callback 
void Setup ( GraphNode  start,
OnPathDelegate  callback 

Member Data Documentation

Vector3 originalStartPoint
Dictionary<GraphNode, GraphNode> parents
bool saveParents = true

If false, will not save any information.

Used by some internal parts of the system which doesn't need it.

GraphNode startNode
Vector3 startPoint

Property Documentation

override bool FloodingPath

The documentation for this class was generated from the following file: