A* Pathfinding Project  4.0.8
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XPath Class Reference

Extended Path. More...

Detailed Description

Extended Path.

This is the same as a standard path but it is possible to customize when the target should be considered reached. Can be used to for example signal a path as complete when it is within a specific distance from the target.

Note
More customizations does make it slower to calculate than an ABPath but not by very much.
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
See Also
Pathfinding.PathEndingCondition

Public Member Functions

 XPath ()
 
- Public Member Functions inherited from ABPath
 ABPath ()
 Default constructor.
 

Static Public Member Functions

static new XPath Construct (Vector3 start, Vector3 end, OnPathDelegate callback=null)
 
- Static Public Member Functions inherited from ABPath
static ABPath Construct (Vector3 start, Vector3 end, OnPathDelegate callback=null)
 Construct a path with a start and end point.
 

Public Attributes

PathEndingCondition endingCondition
 Ending Condition for the path.
 
- Public Attributes inherited from ABPath
bool calculatePartial
 Calculate partial path if the target node cannot be reached.
 
GraphNode endNode
 End node of the path.
 
Vector3 endPoint
 End point of the path.
 
Vector3 originalEndPoint
 End Point exactly as in the path request.
 
Vector3 originalStartPoint
 Start Point exactly as in the path request.
 
Int3 startIntPoint
 Start point in integer coordinates.
 
GraphNode startNode
 Start node of the path.
 
Vector3 startPoint
 Start point of the path.
 
- Public Attributes inherited from Path
OnPathDelegate callback
 Callback to call when the path is complete.
 
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.
 
ITraversalProvider traversalProvider
 Provides additional traversal information to a path request.
 
List< Vector3 > vectorPath
 Holds the (possibly post processed) path as a Vector3 list.
 

Protected Member Functions

override void CalculateStep (long targetTick)
 Calculates the path until completed or until the time has passed targetTick.
 
override void CompletePathIfStartIsValidTarget ()
 The start node need to be special cased and checked here if it is a valid target.
 
override bool EndPointGridGraphSpecialCase (GraphNode endNode)
 Applies a special case for grid nodes.
 
override void Reset ()
 Reset all values to their default values.
 
- Protected Member Functions inherited from ABPath
override void Cleanup ()
 Always called after the path has been calculated.
 
override void Initialize ()
 Initializes the path.
 
override void Prepare ()
 Prepares the path.
 
void UpdateStartEnd (Vector3 start, Vector3 end)
 Sets the start and end points.
 
void Setup (Vector3 start, Vector3 end, OnPathDelegate callbackDelegate)
 
- 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.
 
virtual void OnEnterPool ()
 Called when the path enters the pool.
 
void PrepareBase (PathHandler pathHandler)
 Prepares low level path variables for calculation.
 
virtual void ReturnPath ()
 Calls callback to return the calculated path.
 
virtual void Trace (PathNode from)
 Traces the calculated path from the end node to the start.
 

Private Member Functions

void ChangeEndNode (GraphNode target)
 Changes the endNode to target and resets some temporary flags on the previous node.
 

Additional Inherited Members

- Protected Attributes inherited from ABPath
int[] endNodeCosts
 Saved original costs for the end node.
 
PathNode partialBestTarget
 Current best target for the partial path.
 
- Package Functions inherited from ABPath
override string DebugString (PathLog logMode)
 Returns a debug string for this path.
 
override uint GetConnectionSpecialCost (GraphNode a, GraphNode b, uint currentCost)
 May be called by graph nodes to get a special cost for some connections.
 
- Package Attributes inherited from Path
float duration
 How long it took to calculate this path in milliseconds.
 
Path next
 Internal linked list implementation.
 
- Properties inherited from ABPath
virtual bool hasEndPoint [get]
 Determines if a search for an end node should be done.
 

Constructor & Destructor Documentation

XPath ( )

Member Function Documentation

override void CalculateStep ( long  targetTick)
protectedvirtual

Calculates the path until completed or until the time has passed targetTick.

Usually a check is only done every 500 nodes if the time has passed targetTick. Time/Ticks are got from System.DateTime.UtcNow.Ticks.

Basic outline of what the function does for the standard path (Pathfinding.ABPath).

while the end has not been found and no error has ocurred
check if we have reached the end
if so, exit and return the path
open the current node, i.e loop through its neighbours, mark them as visited and put them on a heap
check if there are still nodes left to process (or have we searched the whole graph)
if there are none, flag error and exit
pop the next node of the heap and set it as current
check if the function has exceeded the time limit
if so, return and wait for the function to get called again

Reimplemented from ABPath.

void ChangeEndNode ( GraphNode  target)
private

Changes the endNode to target and resets some temporary flags on the previous node.

Also sets endPoint to the position of target.

override void CompletePathIfStartIsValidTarget ( )
protectedvirtual

The start node need to be special cased and checked here if it is a valid target.

Reimplemented from ABPath.

static new XPath Construct ( Vector3  start,
Vector3  end,
OnPathDelegate  callback = null 
)
static
override bool EndPointGridGraphSpecialCase ( GraphNode  closestWalkableEndNode)
protectedvirtual

Applies a special case for grid nodes.

Assume the closest walkable node is a grid node. We will now apply a special case only for grid graphs. In tile based games, an obstacle often occupies a whole node. When a path is requested to the position of an obstacle (single unwalkable node) the closest walkable node will be one of the 8 nodes surrounding that unwalkable node but that node is not neccessarily the one that is most optimal to walk to so in this special case we mark all nodes around the unwalkable node as targets and when we search and find any one of them we simply exit and set that first node we found to be the 'real' end node because that will be the optimal node (this does not apply in general unless the heuristic is set to None, but for a single unwalkable node it does). This also applies if the nearest node cannot be traversed for some other reason like restricted tags.

Returns
True if the workaround was applied. If this happens the endPoint, endNode, hTarget and hTargetNode fields will be modified.

Image below shows paths when this special case is applied. The path goes from the white sphere to the orange box.

Image below shows paths when this special case has been disabled

Reimplemented from ABPath.

override void Reset ( )
protectedvirtual

Reset all values to their default values.

All inheriting path types must implement this function, resetting ALL their variables to enable recycling of paths. Call this base function in inheriting types with base.Reset ();

Reimplemented from ABPath.

Member Data Documentation

PathEndingCondition endingCondition

Ending Condition for the path.

The ending condition determines when the path has been completed. Can be used to for example signal a path as complete when it is within a specific distance from the target.

If ending conditions are used that are not centered around the endpoint of the path you should also switch the heuristic to None to make sure that optimal paths are still found. This has quite a large performance impact so you might want to try to run it with the default heuristic and see if the path is optimal in enough cases.


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