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Unity 5.x Game AI Programming Cookbook
Unity 5.x Game AI Programming Cookbook

Unity 5.x Game AI Programming Cookbook: Build and customize a wide range of powerful Unity AI systems with over 70 hands-on recipes and techniques

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Profile Icon Jorge Palacios Profile Icon Jorge Elieser P Garrido
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Profile Icon Jorge Palacios Profile Icon Jorge Elieser P Garrido
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Paperback Feb 2025 278 pages 1st Edition
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€36.99
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Unity 5.x Game AI Programming Cookbook

Chapter 2. Navigation

In this chapter, we will cover the following recipes:

  • Representing the world with grids
  • Representing the world with Dirichlet domains
  • Representing the world with points of visibility
  • Representing the world with a self-made navigation mesh
  • Finding your way out of a maze with DFS
  • Finding the shortest path in a grid with BFS
  • Finding the shortest path with Dijkstra
  • Finding the best-promising path with A*
  • Improving A* for memory: IDA*
  • Planning navigation in several frames: time-sliced search
  • Smoothing a path

Introduction

In this chapter, we will learn path-finding algorithms for navigating complex scenarios. Game worlds are usually complex structures; whether a maze, an open world, or everything in between. That's why we need different techniques for approaching these kinds of problems.

We'll learn some ways of representing the world using different kinds of graph structures, and several algorithms for finding a path, each aimed at different situations.

It is worth mentioning that path-finding algorithms rely on techniques such as Seek and Arrive, learnt in the previous chapter, in order to navigate the map.

Representing the world with grids

A grid is the most used structure for representing worlds in games because it is easy to implement and visualize. However, we will lay the foundations for advanced graph representations while learning the basis of graph theory and properties.

Getting ready

First, we need to create an abstract class called Graph, declaring the virtual methods that every graph representation implements. It is done this way because, no matter how the vertices and edges are represented internally, the path-finding algorithms remain high-level, thus avoiding the implementation of the algorithms for each type of graph representation.

This class works as a parent class for the different representations to be learned in the chapter and it's a good starting point if you want to implement graph representations not covered in the book.

The following is the code for the Graph class:

  1. Create the backbone with the member values:
    using UnityEngine;
    using System.Collections;
    using System...

Representing the world with Dirichlet domains

Also called a Voronoi polygon, a Dirichlet domain is a way of dividing space into regions consisting of a set of points closer to a given seed point than to any other. This graph representation helps in distributing the space using Unity's primitives or existing meshes, thus not really adhering to the definition, but using the concept as a means to an end. Dirichlet domains are usually mapped using cones for delimiting the area of a given vertex, but we're adapting that principle to our specific needs and tool.

Representing the world with Dirichlet domains

Example of a Voronoi Diagram or Voronoi Polygon

Getting ready

Before building our new Graph class, it's important to create the VertexReport class, make some modifications to our Graph class, and add the Vertex tag in the project:

  1. Prepend the VertexReport class to the Graph class specification, in the same file:
    public class VertexReport
    {
        public int vertex;
        public GameObject obj;
        public VertexReport(int vertexId...

Representing the world with points of visibility

This is another widely-used technique for world representation based on points located throughout the valid area of navigation, whether manually placed or automated via scripting. We'll be using manually-placed points connected automatically via scripting.

Getting ready

Just like the previous representation, it's important to have several things in order before continuing:

  • Having the Edge class prepended to the Graph class in the same file
  • Defining the GetEdges function in the Graph class
  • Having the Vertex class

Note

The vertex objects in the scene must have a collider component attached to them, as well as the Vertex tag assigned. It's recommended for them to be unitary Sphere primitives.

How to do it...

We'll be creating the graph representation class as well as a custom Vertex class:

  1. Create the VertexVisibility class deriving from Vertex:
    using UnityEngine;
    using System.Collections.Generic;
    
    public class VertexVisibility : Vertex...

Representing the world with a self-made navigation mesh

Sometimes, a custom navigation mesh is necessary for dealing with difficult situations such as different types of graphs, but placing the graph's vertices manually is troublesome because it requires a lot of time to cover large areas.

We will learn how to use a model's mesh in order to generate a navigation mesh based on its triangles' centroids as vertices, and then leverage the heavy lifting from the previous recipe we learned.

Getting ready

This recipe requires some knowledge of custom editor scripting and understanding and implementing the points of visibility in the graph representation. Also, it is worth mentioning that the script instantiates a CustomNavMesh game object automatically in the scene and requires a prefab assigned, just like any other graph representation.

Finally, it's important to create the following class, deriving from GraphVisibility:

using UnityEngine;
using System.Collections;
using System...

Finding your way out of a maze with DFS

The Depth-First Search (DFS) algorithm is a path-finding technique suitable for low-memory devices. Another common use is to build mazes with a few modifications to the list of nodes visited and discovered, however the main algorithm stays the same.

Getting ready

This is a high-level algorithm that relies on each graph's implementation of the general functions, so the algorithm is implemented in the Graph class.

It is important to

How to do it...

Even though this recipe is only defining a function, please take into consideration the comments in the code to understand the indentation and code flow for effectively:

  1. Declare the GetPathDFS function:
    public List<Vertex> GetPathDFS(GameObject srcObj, GameObject dstObj)
    {
        // next steps
    }
  2. Validate if input objects are null:
    if (srcObj == null || dstObj == null)
        return new List<Vertex>();
  3. Declare and initialize the variables we need for the algorithm:
    Vertex src = GetNearestVertex(srcObj.transform...

Introduction


In this chapter, we will learn path-finding algorithms for navigating complex scenarios. Game worlds are usually complex structures; whether a maze, an open world, or everything in between. That's why we need different techniques for approaching these kinds of problems.

We'll learn some ways of representing the world using different kinds of graph structures, and several algorithms for finding a path, each aimed at different situations.

It is worth mentioning that path-finding algorithms rely on techniques such as Seek and Arrive, learnt in the previous chapter, in order to navigate the map.

Representing the world with grids


A grid is the most used structure for representing worlds in games because it is easy to implement and visualize. However, we will lay the foundations for advanced graph representations while learning the basis of graph theory and properties.

Getting ready

First, we need to create an abstract class called Graph, declaring the virtual methods that every graph representation implements. It is done this way because, no matter how the vertices and edges are represented internally, the path-finding algorithms remain high-level, thus avoiding the implementation of the algorithms for each type of graph representation.

This class works as a parent class for the different representations to be learned in the chapter and it's a good starting point if you want to implement graph representations not covered in the book.

The following is the code for the Graph class:

  1. Create the backbone with the member values:

    using UnityEngine;
    using System.Collections;
    using System.Collections...

Representing the world with Dirichlet domains


Also called a Voronoi polygon, a Dirichlet domain is a way of dividing space into regions consisting of a set of points closer to a given seed point than to any other. This graph representation helps in distributing the space using Unity's primitives or existing meshes, thus not really adhering to the definition, but using the concept as a means to an end. Dirichlet domains are usually mapped using cones for delimiting the area of a given vertex, but we're adapting that principle to our specific needs and tool.

Example of a Voronoi Diagram or Voronoi Polygon

Getting ready

Before building our new Graph class, it's important to create the VertexReport class, make some modifications to our Graph class, and add the Vertex tag in the project:

  1. Prepend the VertexReport class to the Graph class specification, in the same file:

    public class VertexReport
    {
        public int vertex;
        public GameObject obj;
        public VertexReport(int vertexId, GameObject obj...

Representing the world with points of visibility


This is another widely-used technique for world representation based on points located throughout the valid area of navigation, whether manually placed or automated via scripting. We'll be using manually-placed points connected automatically via scripting.

Getting ready

Just like the previous representation, it's important to have several things in order before continuing:

  • Having the Edge class prepended to the Graph class in the same file

  • Defining the GetEdges function in the Graph class

  • Having the Vertex class

Note

The vertex objects in the scene must have a collider component attached to them, as well as the Vertex tag assigned. It's recommended for them to be unitary Sphere primitives.

How to do it...

We'll be creating the graph representation class as well as a custom Vertex class:

  1. Create the VertexVisibility class deriving from Vertex:

    using UnityEngine;
    using System.Collections.Generic;
    
    public class VertexVisibility : Vertex
    {
        void Awake...

Representing the world with a self-made navigation mesh


Sometimes, a custom navigation mesh is necessary for dealing with difficult situations such as different types of graphs, but placing the graph's vertices manually is troublesome because it requires a lot of time to cover large areas.

We will learn how to use a model's mesh in order to generate a navigation mesh based on its triangles' centroids as vertices, and then leverage the heavy lifting from the previous recipe we learned.

Getting ready

This recipe requires some knowledge of custom editor scripting and understanding and implementing the points of visibility in the graph representation. Also, it is worth mentioning that the script instantiates a CustomNavMesh game object automatically in the scene and requires a prefab assigned, just like any other graph representation.

Finally, it's important to create the following class, deriving from GraphVisibility:

using UnityEngine;
using System.Collections;
using System.Collections.Generic...

Finding your way out of a maze with DFS


The Depth-First Search (DFS) algorithm is a path-finding technique suitable for low-memory devices. Another common use is to build mazes with a few modifications to the list of nodes visited and discovered, however the main algorithm stays the same.

Getting ready

This is a high-level algorithm that relies on each graph's implementation of the general functions, so the algorithm is implemented in the Graph class.

It is important to

How to do it...

Even though this recipe is only defining a function, please take into consideration the comments in the code to understand the indentation and code flow for effectively:

  1. Declare the GetPathDFS function:

    public List<Vertex> GetPathDFS(GameObject srcObj, GameObject dstObj)
    {
        // next steps
    }
  2. Validate if input objects are null:

    if (srcObj == null || dstObj == null)
        return new List<Vertex>();
  3. Declare and initialize the variables we need for the algorithm:

    Vertex src = GetNearestVertex(srcObj.transform...
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Key benefits

  • *Empower your agent with decision making capabilities using advanced minimaxing and Negamaxing techniques
  • Discover how AI can be applied to a wide range of games to make them more interactive.
  • *Instigate vision and hearing abilities in your agent through collider based and graph based systems

Description

Unity 5 comes fully packaged with a toolbox of powerful features to help game and app developers create and implement powerful game AI. Leveraging these tools via Unity’s API or built-in features allows limitless possibilities when it comes to creating your game’s worlds and characters. This practical Cookbook covers both essential and niche techniques to help you be able to do that and more. This Cookbook is engineered as your one-stop reference to take your game AI programming to the next level. Get to grips with the essential building blocks of working with an agent, programming movement and navigation in a game environment, and improving your agent's decision making and coordination mechanisms - all through hands-on examples using easily customizable techniques. Discover how to emulate vision and hearing capabilities for your agent, for natural and humanlike AI behaviour, and improve them with the help of graphs. Empower your AI with decision-making functions through programming simple board games such as Tic-Tac-Toe and Checkers, and orchestrate agent coordination to get your AIs working together as one.

Who is this book for?

This book is intended for those who already have a basic knowledge of Unity and are eager to get more tools under their belt to solve AI and gameplay-related problems.

What you will learn

  • * Use techniques such as A*and A*mbush to empower your agents with path finding capabilities.
  • * Create a representation of the world and make agents navigate it
  • * Construct decision-making systems to make the agents take different actions
  • * Make different agents coordinate actions and create the illusion of technical behavior
  • * Simulate senses and apply them in an awareness system
  • * Design and implement AI in board games such as Tic-Tac-Toe and Checkers
  • * Implement efficient prediction mechanism in your agents with algorithms such as N-Gram predictor and naïve Bayes classifier
  • * Understand and analyze how the influence maps work.
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Last updated date : Feb 11, 2025
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Product Details

Last updated date : Feb 11, 2025
Publication date : Mar 31, 2016
Length: 278 pages
Edition : 1st
Language : English
ISBN-13 : 9781783553570
Vendor :
Unity Technologies
Tools :

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Table of Contents

9 Chapters
1. Behaviors – Intelligent Movement Chevron down icon Chevron up icon
2. Navigation Chevron down icon Chevron up icon
3. Decision Making Chevron down icon Chevron up icon
4. Coordination and Tactics Chevron down icon Chevron up icon
5. Agent Awareness Chevron down icon Chevron up icon
6. Board Games AI Chevron down icon Chevron up icon
7. Learning Techniques Chevron down icon Chevron up icon
8. Miscellaneous Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon
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