Lua Game Development Cookbook

Table of Contents

Lua Game Development Cookbook

Credits

About the Author

About the Reviewer

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Preface

What this book covers

What you need for this book

Who this book is for

Sections

Getting ready

How to do it…

How it works…

There's more…

See also

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. Basics of the Game Engine

Introduction

Preparing a basic file structure for the game engine

Getting ready

How to do it…

How it works…

Making a stack

Getting ready

How to do it…

How it works…

Making a queue

Getting ready

How to do it…

How it works…

Making a prioritized queue

Getting ready

How to do it…

How it works…

Extending ipairs for use in sparse arrays

Getting ready

How to do it…

How it works…

Creating Lua modules

Getting ready

How to do it…

A module that returns a table as an interface

A module in the form of an object

A module in the form of a singleton object

How it works…

Handling errors with pcall, xpcall, and assert

Getting ready

How to do it…

How it works…

Using Lua with existing projects written in C/C++

Getting ready

How to do it…

Initializing the Lua state

Creating a Lua module in C/C++

Passing variables from C/C++ into the Lua environment

Passing variables from the Lua environment to C/C++

Making the C++ class accessible from Lua with Lutok2

How it works…

Getting LuaSDL for libSDL 1.2

Getting ready

How to do it…

There's more…

Designing the main application loop with LuaSDL

Getting ready

How to do it…

How it works…

2. Events

Introduction

Processing input events with LuaSDL

Getting ready

How to do it…

Event handling with the if-then-else chain

Event handling with an associative array

How it works…

See also

Using the keyboard input

Getting ready

How to do it…

Normal keys

Modifier keys

How it works…

See also

Using the relative mouse position

Getting ready

How to do it…

There's more…

Using the absolute mouse position

How to do it…

Using timers

Getting ready

How to do it…

How it works…

There's more…

3. Graphics – Common Methods

Introduction

Creating a window in libSDL

Getting ready

How to do it…

How it works…

Creating surfaces

Getting ready

How to do it…

How it works…

There's more…

Surfaces manipulation

Getting ready

How to do it…

How it works…

Using colors

Getting ready

How to do it…

How it works…

Cursor manipulation

Getting ready

How to do it…

How it works…

See also

Initializing the graphics mode with OpenGL

Getting ready

How to do it…

How it works…

Getting OpenGL information

Getting ready

How to do it…

Getting the OpenGL version

Getting the graphic card vendor

Getting the graphic card name

Getting the extensions list

How it works…

Using OpenGL extensions with GLEW and Lua

Getting ready

How to do it…

How it works…

Loading images with SDL_image

Getting ready

How to do it…

How it works…

Creating textures

Getting ready

How to do it…

How it works…

There's more…

Loading and using bitmap fonts

Getting ready

How to do it…

How it works…

There's more…

See also

Loading and using TrueType fonts

Getting ready

How to do it…

How it works…

See also

Displaying the text

Getting ready

How to do it…

How it works…

See also

Creating texture atlas with the rover-design pattern

Getting ready

How to do it…

How it works…

Using tiles and tilesets in the game

Getting ready

How to do it…

How it works…

See also

4. Graphics – Legacy Method with OpenGL 1.x–2.1

Introduction

Drawing primitives in immediate mode

Getting ready

How to do it…

Drawing points

Drawing lines

Drawing line strips

Drawing line loops

Drawing triangles

Drawing triangle strips

Drawing triangle fans

Drawing quads

Drawing quad strips

Drawing polygons

How it works…

See also

Setting up blending

Getting ready

How to do it…

Additive blending

Subtractive blending

Alpha blending

How it works…

Moving, rotating, and scaling objects

Getting ready

How to do it…

How it works…

The identity matrix

The translation matrix

The scale matrix

The rotation matrix

There's more…

See also

Setting up the orthogonal and perspective cameras

Getting ready

How to do it…

The orthogonal mode

The perspective mode

How it works…

There's more…

See also

Setting up materials

Getting ready

How to do it…

How it works…

There's more…

See also

Setting up lighting

Getting ready

How to do it…

How it works…

There's more…

See also

Using display lists

Getting ready

How to do it…

How it works…

See also

Setting up the vertex buffer

Getting ready

How to do it…

How it works…

There's more…

5. Graphics – Modern Method with OpenGL 3.0+

Introduction

Loading and using GLSL shaders

Getting ready

How to do it…

How it works…

See also

Using uniform variables with shaders

Getting ready

How to do it…

Writing into uniform variables

Reading from uniform variables

How it works…

Writing a vertex shader

Getting ready

How to do it…

How it works…

There's more…

See also

Writing a fragment (pixel) shader

Getting ready

How to do it…

How it works…

There's more…

See also

Drawing primitives using vertex buffers

Getting ready

How to do it…

Vertex positions

Vertex colors

Vertex texture coordinates

How it works…

There's more…

See also

Rendering to texture

Getting ready

How to do it…

The render buffer with the color attachment

The render buffer with the depth attachment

How it works…

See also

Applying highlights and shadows to the scene

Getting ready

How to do it…

Vertex shader

Fragment shader

How it works…

See also

Bumpmapping

Getting ready

How to do it…

Vertex shader

Fragment shader

How it works…

There's more…

See also

6. The User Interface

Introduction

Drawing a simple window

Getting ready

How to do it…

How it works…

Moving the window

Getting ready

How to do it…

How it works…

Using the window hierarchy

Getting ready

How to do it…

Child window rendering

Event propagation

How it works…

See also

Showing the part of the window with the stencil test and window content scrolling

Getting ready

How to do it…

How it works…

See also

Window controls and interaction

Getting ready

How to do it…

Button

Edit box

How it works…

There's more…

See also

7. Physics and Game Mechanics

Introduction

Using Box2D with Lua

Getting ready

How to do it…

How it works...

Using vector math

Getting ready

How to do it…

How it works…

Choosing the correct vector scaling for the physics engine

Getting ready

How to do it…

How it works…

Creating static and dynamic objects

Getting ready

How to do it…

How it works…

There's more…

Setting up object properties

Getting ready

How to do it…

Movement damping

Object gravity scale

Fixed rotation

Object sleeping

Object mass and rotational inertia

Friction

Restitution

Density

How it works…

Moving objects

Getting ready

How to do it…

The continual force

Impulses

Object velocity information

How it works…

Setting up bullets

Getting ready

How to do it…

How it works…

Running the physics simulation

Getting ready

How to do it…

The fixed-time step

The dynamic-time step

How it works…

There's more…

Detecting object collision

Getting ready

How to do it…

How it works…

The beginContact callback

The endContact callback

The preSolve callback

The postSolve callback

There's more…

Setting up object collision filtering

Getting ready

How to do it…

How it works…

There's more…

Setting up object joints

Getting ready

How to do it…

Revolute joint

The prismatic joint

The distance joint

The rope joint

The weld joint

The pulley joint

The wheel joint

The gear joint

The motor joint

The mouse joint

The friction joint

How it works…

See also

8. Artificial Intelligence

Introduction

A simple pathfinding algorithm for a maze

Getting ready

How to do it…

Maze generation

Maze solving

How it works…

Pathfinding for tile-based environments with obstacles

Getting ready

How to do it…

How it works…

Heuristic

There's more…

See also

Using a fuzzy logic for decision making

Getting ready

How to do it…

A fuzzy set

A linguistic variable

A rule

A solver

A usage

How it works…

9. Sounds and Networking

Introduction

Initializing the audio subsystem

Getting ready

How to do it…

How it works…

Playing sound samples

Getting ready

How to do it…

How it works…

There's more…

See also

Playing background music

Getting ready

How to do it…

How it works…

See also

Network communication with ZeroMQ

Getting ready

How to do it…

How it works…

Creating a basic client-server architecture

Getting ready

How to do it…

The server part

The client part

How it works…

Sending messages to many hosts at once

Getting ready

How to do it…

The publisher part

The subscriber part

How it works…

Communication between threads

Getting ready

How to do it…

How it works…

Index

Lua Game Development Cookbook

Lua Game Development Cookbook

Copyright © 2015 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: July 2015

Production reference: 1200715

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham B3 2PB, UK.

ISBN 978-1-84951-550-4

www.packtpub.com

Credits

Author

Mário Kašuba

Reviewers

Victor Andrade de Oliveira

Anthony Zhang

Commissioning Editor

Sarah Cullington

Acquisition Editor

Kevin Colaco

Content Development Editor

Govindan K

Technical Editor

Vivek Arora

Copy Editors

Merilyn Pereira

Laxmi Subramanian

Project Coordinator

Sanjeet Rao

Proofreader

Safis Editing

Indexer

Rekha Nair

Graphics

Jason Monteiro

Abhinash Sahu

Production Coordinator

Manu Joseph

Cover Work

Manu Joseph

About the Author

Mário Kašuba achieved a master's degree in applied informatics at Slovak Technical University in Bratislava, where he used the Lua language in 3D robotics simulations and developed various multimedia applications along with a few computer games.

Currently, he is the co-owner and chief information officer of an IT Academy company, while he also leads courses on C/C++, PHP, Linux, Databases, Typo3, Silverstripe CMS, VMware virtualization, and the Microsoft Windows Server operating system.

He also works as the head web developer and system administrator for the web portal http://www.rodinka.sk/.

I would like to acknowledge the support provided by my family, friends, and colleagues. I am particularly grateful to the members of the Lua users community who helped me with the reviewing process. I would also like to thank the staff at Packt Publishing for their guidance and valuable support.

About the Reviewer

Victor Andrade de Oliveira is a Brazilian computer engineer who graduated from the Institute for Higher Studies of the Amazon (IESAM) with a vast knowledge of the Lua language and has worked for more than 5 years in the development of interactive and embedded applications for Ginga—the middleware of the Japanese-Brazilian Digital TV System (ISDB-TB) and ITU-T Recommendation for IPTV services.

Anthony Zhang is a programmer, electronics hobbyist, and digital artist who has an unhealthy obsession with robotics. If you want to hear him talk for hours on end, ask him something about AI, physical computing, obscure processor functionality, and computer graphics. These days, you'll find him working on video games, doing ridiculous things with microcontrollers, and attempting to add LEDs where they don't belong.

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Preface

Game development is one of the most complex processes in the world as it requires a wide set of skills such as programming, math, physics, art, sound engineering, management, marketing, and many more. Even with modern technologies, it may take from a few hours to several years to create a game. This depends on the game complexity and tools available.

Computer games are usually based on a mix of simple concepts, which are turned into an enjoyable experience. The first step in making a good game is a game prototype. These can be made with the help of various game engines. However, learning how to use a game engine to the full extent may require you to study how it actually works. This way you have to rely on the available documentation and features that the game engine provides. Many game engines today provide a scripting language as a tool to implement certain game mechanics or to extend the game engine itself with new features.

The Lua programming language is gaining popularity in the game industry mainly due to its simplicity and efficiency. Most of the time, it's used only for simple tasks such as NPC dialogs, user interface, or custom game events. However, with additional Lua modules, you can create your own full-fledged game engine that can use almost all the capabilities of the modern computer hardware.

In this book, you'll find a set of recipes with solutions to the most common problems you may encounter while creating games with the Lua language.

The best way to learn something is to play with it. Therefore, each recipe is paired with simple demo applications that will help you understand the topic covered. You may even use these demo samples to create your own game prototype in no time.

All sample applications are available in the digital content of this book.

What this book covers

Chapter 1, Basics of the Game Engine, covers important algorithms and the basic design of a game engine written in the Lua programming language, as well as LuaSDL multimedia module preparation, which is the main part of all the recipes in this book.

Chapter 2, Events, deals with handling input events that are an important part of any game engine.

Chapter 3, Graphics – Common Methods, contains basic concepts used in computer graphics. You'll learn how to initialize the graphics mode, use basic OpenGL functions, load images, create textures, and draw text on the screen.

Chapter 4, Graphics – Legacy Method with OpenGL 1.x-2.1, explains how to use the intermediate mode of OpenGL, which is intended for use on older GPUs. Even when this mode is currently deprecated, it holds important information that is vital when using modern versions of OpenGL. It may be used as a precursor to more advanced topics in Chapter 5, Graphics – Modern Method with OpenGL 3.0+.

Chapter 5, Graphics – Modern Method with OpenGL 3.0+, covers the basics of using the GLSL shading language with the Lua language to draw various scenes. You'll also learn how to use per-pixel lighting, render into textures and apply surface effects with normal maps.

Chapter 6, The User Interface, covers the implementation of the custom user interface from simple windows to window controls.

Chapter 7, Physics and Game Mechanics, explains how to prepare and use the LuaBox2D module with the Lua language for physics simulation. The Box2D library is quite popular in modern side-scrolling games mainly because it offers great flexibility.

Chapter 8, Artificial Intelligence, deals with pathfinding algorithms and fuzzy logic. You'll learn how pathfinding works in games with simple maze or even tiled environments. More advanced topics cover decision making with fuzzy logic. In combination with pathfinding algorithms, you can create intelligent game opponents that won't jump into a lava lake at the first opportunity.

Chapter 9, Sounds and Networking, covers how to initialize the sound card, play sounds, and music. The second part covers network communication with the high-performance ZeroMQ library. It contains many improvements over traditional socket communication and it's used by companies such as AT&T, Cisco, EA, Zynga, Spotify, NASA, Microsoft, and CERN.

What you need for this book

Sample demonstrations for recipes require the Microsofts Windows or Linux operating systems. Unfortunately, Mac OS is not currently supported.

If you intend to build binary Lua modules from this book, you'll need the C/C++ compiler along with the recent version of the CMake building system. Additionally, Linux users will need to install development packages for the XOrg display server in order to include the graphical output.

However, it's not necessary to do so as binary Lua modules are included in code files for this book.

The recipes in Chapter 5, Graphics – Modern Method with OpenGL 3.0+, require a graphic card released after 2010 with support for OpenGL 3.3.

Who this book is for

This book is for all programmers and game enthusiasts who want to stop dreaming about creating a game, and actually create one from scratch.

The reader should know the basics of programming and using the Lua language. Knowledge of the C/C++ programming language is not necessary, but it's strongly recommended in order to write custom Lua modules extending game engine capabilities or to rewrite parts of the Lua code into a more efficient form.

Algebra and matrix operations are required in order to understand advanced topics in Chapter 4, Graphics – Legacy Method with OpenGL 1.x-2.1 and Chapter 5, Graphics – Modern Method with OpenGL 3.0+.

Sample demonstrations are coupled with binary libraries for Windows and Linux operating systems for convenience.

Sections

In this book, you will find several headings that appear frequently (Getting ready, How to do it, How it works, There's more, and See also).

To give clear instructions on how to complete a recipe, we use these sections as follows:

Getting ready

This section tells you what to expect in the recipe, and describes how to set up any software or any preliminary settings required for the recipe.

How to do it…

This section contains the steps required to follow the recipe.

How it works…

This section usually consists of a detailed explanation of what happened in the previous section.

There's more…

This section consists of additional information about the recipe in order to make the reader more knowledgeable about the recipe.

See also

This section provides helpful links to other useful information for the recipe.

Conventions

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: We can include other contexts through the use of the include directive.

A block of code is set as follows:

local sum_of_numbers = 0

local iterations = 3

for i=1,iterations do

  sum_of_numbers = sum_of_numbers + 1/iterations

  print((%f):format(sum_of_numbers))

end

-- is the result equal to 1?

print(Sum equals to 1?, sum_of_numbers == 1)