Learning Game AI Programming with Lua

Book Image

Learning Game AI Programming with Lua

By : David Young

Book Image

Learning Game AI Programming with Lua

By: David Young

Overview of this book

Learning Game AI Programming with Lua

Learning Game AI Programming with Lua

Credits

About the Author

About the Author

About the Reviewers

About the Reviewers

www.PacktPub.com

www.PacktPub.com

Preface

Free Chapter

Getting Started with AI Sandbox

Getting Started with AI Sandbox

Introduction to AI sandbox

Creating and Moving Agents

Creating and Moving Agents

Creating a new sandbox project

Setting up the file structure

Extending the SandboxApplication class

Running your sandbox for the first time

Creating a new Decoda project

Configuring Decoda's run executable

Creating a sandbox Lua script

Shooting blocks

Creating an agent Lua script

Agent properties

Agents' movement

Agent-steering forces

Avoiding blocks and agents

Creating a group of followers

Summing steering forces

Character Animations

Character Animations

Skeletons and meshes

Attaching meshes to bones

Animation clips

Manipulating animations

Animation blending

Animation state machine (ASM)

Building a weapon animation state machine

Building a soldier animation state machine

Updating animation state machines

Playing with states

Mind Body Control

Mind Body Control

Creating a body

Adding callbacks to the animation state machine

Getting our soldier to shoot

Getting our soldier to run

Creating a brain

Direct animation control

A simple, finite state machine

Indirect animation control

Running the obstacle course

Navigation

Creating a navigation mesh

Pathfinding on a navigation mesh

The path information

Adding random pathfinding to our soldier

Creating additional navigation meshes

Decision Making

Decision Making

Creating userdata

Creating actions

Creating evaluators

Decision structures

Building a decision tree

Creating a decision tree agent

Finite state machines

Building a finite state machine

Creating a finite state machine agent

Strengths of finite state machines

Pitfalls of finite state machines

Creating a behavior tree object

Building a behavior tree

Creating a behavior tree agent

Strengths of behavior trees

Pitfalls of behavior trees

Knowledge Representation

Knowledge Representation

Knowledge sources

Creating soldier knowledge sources

Constructing a soldier blackboard

Updating decision evaluators

Updating behavior actions

Perception

Managing events

Creating agent senses

Agent visibility

Agent sighting events

Handling new agent sightings

Agent auditory senses

Auditory events

Handling auditory events

Decaying blackboard events

Decaying auditory events

Team communications

Updating agent behaviors

Tactics

Constructing an influence map

Drawing influence maps

Accessing influences

Clearing influences

Spreading influences

Influence map layers

Updating the influence map

Soldier tactics

Scoring team influences

Scoring dangerous areas

Index

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Creating a behavior tree object

Creating a behavior tree object is simple, as it primarily consists of a root node, evaluation function, and update function:

BehaviorTree.lua:

require "BehaviorTreeNode"

BehaviorTree = {};

local _EvaluateSelector;
local _EvaluateSequence;

function BehaviorTree.SetNode(self, node)
    tree.node_ = node;
end

function BehaviorTree.new()
    local tree = {};
    
    -- The BehaviorTree's data members.
    tree.currentNode_ = nil;
    tree.node_ = nil;
    
    return tree;
end

Behavior tree helper functions

Four primary evaluators are used to process the behavior tree structure: selector evaluation, sequence evaluation, actual node evaluation, and finally, a continue evaluation function that continues where a sequence's child finishes:

BehaviorTree.lua:

local EvaluateSelector;
local EvaluateSequence;

Selector evaluation

As selectors only return false if all child nodes have executed without returning true, we can iterate over all children and return the first...