Gravy.PathFinder 0.1.1-alpha

Path Finder

A simple to use collection of various path finding algorithms.

This is a work in progress. All API's are subject to change significantly.

Goals

The goal of this project is to provide a variety of easy to use and well performing path finding algorithms that can be used with little modification of a projects existing code.

Why?

A* and other graph solvers are well documented, and honestly pretty "easy" to implement right? Well as I found out, not exactly. Yes they are well documented, but actually implementing them with good performance is another story. Also, most implementations I found were very specific to the project they were implemented in, and did not allow for much " configuration" of how the solver would perform. This project was born from that frustration.

Installing

Install from NuGet

via .NET CLI

dotnet add package Gravy.PathFinder --version 0.1.1-alpha

via PackageReference

<PackageReference Include="Gravy.PathFinder" Version="0.1.1-alpha"/>

WARNING Until v1 is release, the API is subject to breaking changes.

Usage

PathFinder uses the term "Graph" to represent any network of connected nodes. A 2d or 3d map is also a graph, with each position on the map being nodes in the graph connected by traversing through the map. A Graph could represent anything though, for example persons in a social network, with friendships allowing traversal through the graph.

View the Api Documentation for a complete reference.

Simple Usage

You can either update the "nodes" of your graph to implement ITraversableNode , or create a INodeTraverser .

To find a path, use one of the included solvers.

using PathFinder.Solvers.Generic;

YourNode fromNode = YourGraph.GetNode();
YourNode toNode = YourGraph.GetNode();

// just get a path using A*
var state = AStar.Solve(fromNode, toNode, out IList path);
if (state == SolverState.Success)
    UsePath(path);

// create a greedy solver and run it manually
// giving time every 100 ticks for other work
// to be completed.
var solver = new Greedy(fromNode, toNode, new YourNodeTraverser());
solver.MaxTicks = 20000;
while (solver.State == SolverState.Incomplete) {
    solver.Start(100); // run 100 ticks
    DoOtherWork();
}
if (solver.State == SolverState.Success)
    MoveEntity(entity, solver.Path)

For an example of ITraversableNode, see SimpleWorld.Map.Position .

For examples of INodeTraverser, see Traversers .

Note: When implementing, it is important to make sure EstimatedCostTo /EstimatedCost returns the best case cost for the best performance.

*Note 2: You must implement either a INodeTraverser, or implement ITraversableNode on your existing graph. If no traverser is given to a solver, and the nodes do not implement ITraversableNode, then the solver will throw an exception.

Solver Types

All Generic solvers implement IGraphSolver .

Solvers.Generic.AStar

An implementation of the traditional A* algorithm with an adjustable greed factor.

The greed factor determines how exhaustive the search will be. Greed factors closer to zero will check more possible nodes, while greater than zero will favor reducing the estimated. A greed factor of one is equivalent to the standard A* method.

Solvers.Generic.Greedy

The greedy solvers traverses a graph ignoring any travel costs and attempts to reduce the remaining distance only. This can be useful to determine if a path is even possible, or in very open graphs with little to no obstacles or movement costs.

Solvers.Generic.BreadthFirst

An exhaustive graph searcher, or crawler. Starts at node and searches every found node until the destination is found. This is really only useful in graphs when an estimation function is impossible, as the A* algorithm with greed ⇐ 1 will always find the best path, at a fraction of the cost of Breadth First.

Node Traversers

All of the generic solvers can be given an INodeTraverser to replace or augment the graphs own traversal methods. An example of when to use an INodeTraverser could be to implement custom traversal patterns in a game on the entities themselves.

Future Plans

• Writing more documentation/guides to using.
• Adding "Dynamic" algorithms which modify their running parameters based on a set of configurable metrics (time to solve, distance remaining, etc).
• Adding "Spatially aware" path finding algorithms (Hierarchical, clustered, ray tracing, etc).
• Adding Thread Safety to the solvers (or maybe thread safe alternatives at the cost of performance).
• Testing in Unity and MonoGame.

License

The MIT License (MIT) Copyright © 2021 Kevin Gravier

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.