EpPathFinding.cs

A jump point search algorithm for grid based games in C#

Original Project

This project is forked from EpPathFinding.cs And inspired by PathFinding.js by Xueqiao Xu and the article by D. Harabor.

Basic Usage

The usage and the demo has been made very similar to PathFinding.js for ease of usage.

You first need to build a grid-map. (For example: width 64 and height 32):

BaseGrid searchGrid = new StaticGrid(64, 32);

By default, every nodes in the grid will NOT allow to be walked through. To set whether a node at a given coordinate is walkable or not, use the SetWalkableAt function.

For example, in order to set the node at (10 , 20) to be walkable, where 10 is the x coordinate (from left to right), and 20 is the y coordinate (from top to bottom):

searchGrid.SetWalkableAt(10, 20, true);
 
// OR
 
searchGrid.SetWalkableAt(new GridPos(10,20),true);  

You may also use in a 2-d array while instantiating the StaticGrid class. It will initiate all the nodes in the grid with the walkability indicated by the array. (true for walkable otherwise not walkable):

bool [][] movableMatrix = new bool [width][];
for(int widthTrav=0; widthTrav< 64; widthTrav++)
{
   movableMatrix[widthTrav]=new bool[height];
   for(int heightTrav=0; heightTrav < 32;  heightTrav++)
   { 
      movableMatrix[widthTrav][heightTrav]=true; 
   }  
}

Grid searchGrid = new StaticGrid(64,32, movableMatrix);

In order to search the route from (10,10) to (20,10), you need to create JumpPointParam class with grid and start/end positions. (Note: both the start point and end point must be walkable):

GridPos startPos=new GridPos(10,10); 
GridPos endPos = new GridPos(20,10);  
JumpPointParam jpParam = new JumpPointParam(searchGrid,startPos,endPos ); 

You can also set/change the start and end positions later. (However the start and end positions must be set before the actual search):

JumpPoinParam jpParam = new JumpPointParam(searchGrid);
jpParam.Reset(new GridPos(10,10), new GridPos(20,10)); 

To find a path, simply run FindPath function with JumpPointParam object created above:

List<GridPos> resultPathList = JumpPointFinder.FindPath(jpParam); 

JumpPointParam class can be used as much as you want with different start/end positions unlike PathFinding.js:

jpParam.Reset(new GridPos(15,15), new GridPos(20,15));
resultPathList = JumpPointFinder.FindPath(jpParam); 

Advanced Usage

Find the path even the end node is unwalkable

When instantiating the JumpPointParam, you may pass in additional parameter to make the search able to find path even the end node is unwalkable grid:

Note that it automatically sets to ALLOW as a default when the parameter is not specified.

JumpPointParam jpParam = new JumpPointParam(searchGrid,EndNodeUnWalkableTreatment.ALLOW);

If iAllowEndNodeUnWalkable is DISALLOW the FindPath will return the empty path if the end node is unwalkable:

JumpPointParam jpParam = new JumpPointParam(searchGrid,EndNodeUnWalkableTreatment.DISALLOW);   

DiagonalMovement.Always (Cross Adjacent Point)

In order to make search able to walk diagonally across corner of two diagonal unwalkable nodes:

JumpPointParam jpParam = new JumpPointParam(searchGrid,EndNodeUnWalkableTreatment.ALLOW,DiagonalMovement.Always);   

DiagonalMovement.IfAtLeastOneWalkable (Cross Corner)

When instantiating the JumpPointParam, to make the search able to walk diagonally when one of the side is unwalkable grid:

JumpPointParam jpParam = new JumpPointParam(searchGrid,EndNodeUnWalkableTreatment.ALLOW,DiagonalMovement.IfAtLeastOneWalkable);   

DiagonalMovement.OnlyWhenNoObstacles

To make it unable to walk diagonally when one of the side is unwalkable and rather go around the corner:

JumpPointParam jpParam = new JumpPointParam(searchGrid,EndNodeUnWalkableTreatment.ALLOW,DiagonalMovement.OnlyWhenNoObstacles);   

DiagonalMovement.Never

To make it unable to walk diagonally:

// Special thanks to Nil Amar for the idea!
JumpPointParam jpParam = new JumpPointParam(searchGrid,EndNodeUnWalkableTreatment.ALLOW,DiagonalMovement.Never);   

Heuristic Functions

The predefined heuristics are Heuristic.EUCLIDEAN (default), Heuristic.MANHATTAN, and Heuristic.CHEBYSHEV.

To use the MANHATTAN heuristic:

JumpPointParam jpParam = new JumpPointParam(searchGrid,EndNodeUnWalkableTreatment.ALLOW, DiagonalMovement.Always, Heuristic.MANHATTAN); 

You can always change the heuristics later with SetHeuristic function:

jpParam.SetHeuristic(Heuristic.MANHATTAN);

Dynamic Grid

For my grid-based game, I had much less walkable grid nodes than un-walkable grid nodes. So above StaticGrid was wasting too much memory to hold un-walkable grid nodes. To avoid the memory waste, I have created DynamicGrid, which allocates the memory for only walkable grid nodes.

(Please note that there is trade off of memory and performance. This degrades the performance to improve memory usage.)

BaseGrid seachGrid = new DynamicGrid();  

You may also use a List of walkable GridPos, while instantiating the DynamicGrid class. It will initiate only the nodes in the grid where the walkability is true:

List<GridPos> walkableGridPosList= new List<GridPos>();
for(int widthTrav=0; widthTrav< 64; widthTrav++)
{
   movableMatrix[widthTrav]=new bool[height];
   for(int heightTrav=0; heightTrav < 32;  heightTrav++)
   {
      walkableGridPosList.Add(new GridPos(widthTrav, heightTrav));
   }
}

BaseGrid searchGrid = new DynamicGrid(walkableGridPosList);  

Rest of the functionality like SetWalkableAt, Reset, etc. are same as StaticGrid.

Dynamic Grid With Pool

In many cases, you might want to reuse the same grid for next search. And this can be extremely useful when used with PartialGridWPool, since you don't have to allocate the grid again.

NodePool nodePool = new NodePool();
BaseGrid seachGrid = new DynamicGridWPool(nodePool);  

Rest of the functionality like SetWalkableAt, Reset, etc. are same as DynamicGrid.

Partial Grid With Pool

As mentioned above, if you want to search only partial of the grid for performance reason, you can use PartialGridWPool. Just give the GridRect which shows the portion of the grid you want to search within.

NodePool nodePool = new NodePool();
...
BaseGrid seachGrid = new PartialGridWPool(nodePool, new GridRect(1,3,15,30);  

Rest of the functionality like SetWalkableAt, Reset, etc. are same as DynamicGridWPool.

IterationType

You may use recursive function or loop function to find the path. This can be simply done by setting IterationType flag in JumpPointParam:

Note that the default is IterationType.LOOP, which uses loop function.

// To use recursive function
JumpPointParam jpParam = new JumpPointParam(...);
jpParam.IterationType = IterationType.RECURSIVE;  

To change back to loop function

// To change back to loop function 
jpParam.IterationType = IterationType.LOOP; 

Extendability

You can also create a sub-class of BaseGrid to create your own way of Grid class to best support your situation.

License

The MIT License

Copyright (c) 2013 Woong Gyu La <[email protected]>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.