Practical Game AI Programming: C# Unity Companion Code from Packt

What the Repository Contains and Who It Is For

PacktPublishing/Practical-Game-AI-Programming is the official code companion for the Packt book 'Practical Game AI Programming.' The README describes it as holding all supporting project files necessary to work through the book from start to finish.

The audience is developers learning Unity3D game AI who are following the book chapter by chapter. The code is not designed for dropping into an existing game; it is structured as discrete per-chapter Unity projects that demonstrate individual techniques in isolation.

The repository contains chapters 3 through 10. Chapters 1 and 2 are absent from the repository, which the README does not explain. Readers expecting all chapters will find eight of the ten covered.

Algorithms and Techniques Across Chapters 3 Through 10

The README lists the subject matter without mapping each topic to a specific chapter. The covered algorithms and techniques include: working with animations, pruning strategies for decision trees, Theta algorithms for generating short and realistic-looking game paths, handling AI behaviour when many characters share a scene, possibility maps, Forward Chaining Plans, the Rete Algorithm, wall distance calculations, and map preprocessing.

Theta pathfinding is notable because it produces paths that do not snap to a navigation grid, making AI movement appear less mechanical than standard A* on tile-based maps. The Rete Algorithm applies to rule-based AI systems and is less commonly covered in introductory game development tutorials.

The README does not specify which chapters contain which algorithms. Readers need the book to know where to look, as the repository offers no index or per-chapter README.

Setting Up Unity3D and Opening the Projects

The README recommends installing a game engine that uses C#. It specifically names Unity3D, noting that a free version is available. Each chapter folder starts with a number followed by an application name, for example Chapter03.

To use the examples, install Unity from Unity's official website, open the Unity Hub, and add each chapter folder as an existing project. The repository provides no build scripts, no Makefile, and no command-line setup. All compilation happens inside the Unity editor after the project is opened.

The README does not specify a minimum Unity version. Because the last push was on 2023-01-24, and Unity releases major editor versions annually with deprecation cycles for older APIs, some examples may produce warnings or errors on current Unity releases. The `Transform.LookAt` and `Vector3.MoveTowards` methods used in the code are long-standing Unity APIs and are unlikely to break, but other methods in later chapters have not been verified against current releases.

A C# Movement and Targeting Example from the Repository

The README includes a C# snippet that illustrates the pattern used in the examples. The code shows a NPC soldier facing a player and moving toward a building while firing backward:

if (playerPosition == "triggerM")
{

  transform.LookAt(playerSoldier); // Face the direction of the   player

 transform.position = Vector3.MoveTowards
  (transform.position,
 buildingPosition.position, walkBack);

 backwardsFire();

}

The snippet demonstrates the two Unity API calls that appear repeatedly in the book's movement chapters: `Transform.LookAt` to orient an agent toward a target, and `Vector3.MoveTowards` to step the agent's position toward a destination at a fixed speed. The `backwardsFire()` call is project-specific and defined elsewhere in the chapter's scripts.

This example is a C# method body, not a standalone Unity script. It runs inside a MonoBehaviour's Update loop, which the book explains in context.

What the Repository Does Not Provide

The README is minimal: it names the book, lists the topics covered, shows one code snippet, and links three related Packt products. There are no per-chapter READMEs, no explanation of project dependencies beyond Unity3D, no screenshots, and no troubleshooting section.

The repository has no GitHub releases and no versioning. The book covers which Unity version was used for each example, but that information is not replicated in the repository. Engineers who want to understand a technique without reading the book will find the code alone insufficient.

There are no tests. The examples are self-contained Unity scenes, not libraries with testable interfaces, so there is no way to verify correctness outside the Unity editor.

Maintenance Status: Last Push January 2023

The last push to this repository was on 2023-01-24. The repository is not archived and has not been deleted, but it receives no updates. Three years is significant for a Unity project: Unity deprecated its legacy Input Manager in favour of the Input System package, updated its NavMesh API, and changed editor scripting patterns in ways that may affect how chapter examples compile.

The MIT licence means the code is free to use, modify, and redistribute. Readers who need to update an example for a newer Unity version are legally free to do so and to share their changes, though the repository shows no sign of accepting pull requests.

Packt publishes a DRM-free PDF for purchasers of the print or Kindle edition, available at the link in the README. That download does not include updated code.

Comparison with Unity's Own Game AI Resources

Unity Technologies publishes its own sample projects through the Unity Asset Store and the official documentation, including NavMesh tutorials and ML-Agents for machine learning-driven characters. Those resources are updated alongside each Unity editor release and are guaranteed to compile without modification, unlike this companion repository.

The advantage of the Packt repository is its algorithm depth. Unity's official NavMesh documentation covers pathfinding at a high level. The book, and by extension this repository, goes into lower-level techniques such as the Rete Algorithm and Forward Chaining Plans that Unity does not document. For developers who want to understand these algorithms in a working C# and Unity context, the book-and-repository combination is more specific than Unity's general tutorials.

Editorial conclusion

This repository suits a reader who has already purchased or is working through 'Practical Game AI Programming' and wants to run the Unity3D examples from chapters 3 through 10. It is not a standalone learning resource: without the book, the code is unexplained. The last push was on 2023-01-24, meaning Unity API changes in the intervening years may require manual fixes to compile. Check that each chapter folder opens without import errors in your version of Unity before building on any example.

Frequently asked questions

Official sources

1. Official README
2. Project repository