CSCE 590E Spring 2007

Game Design II

By Jijun Tang

Announcements

We will meet in 2A21 on Wednesday Please bring laptops on Wednesday Please install Adobe Flash 8.0

professional trial version Think about group name and log

Design of Everyday Things

Norman’s five principles of design Visibility

Making the parts visible Mappings

Understandable relationships between controls and actions

Affordances The perceived uses of an object

Constraints Prevent the user from doing things they shouldn’t

Feedback Reporting what has been done and accomplished

System Components

Objects Pieces of a system

Attributes Properties determining what objects are

Behaviors Actions the objects can perform

Relationships How the behavior and attributes of objects affect

each other while the system operates

Positive Feedback

Amplify changes Leads to runaway behavior Difficult to make use of

From Bob Craig

Negative feedback

Counteracts changes Leads to goal seeking behaviors Most common form in systems

From Bob Craig

Game Saves

Save triggers: automatically saved at certain points Disadvantage: Player has little control

Save-anywhere Allow the player to save the state at any point in the game Disadvantage: System needs to save many different

variables, also may make it too easy for the player Save points:

Save only the accumulated points Disadvantage: Rather limited

Coded text saves to save a bit space Do you really want user to save?

Audiences

Target audience Group of expected consumers Age, gender income … What does your audience know? What does your audience demand?

Demographics Study of relevant economic and social statistics

about a given population Demographic variables

The relevant factors

Design Procedure

Waterfall method Development methodology Design and production are broken into phases

Iterative development Practice of producing things incrementally Refining and re-refining the product May iterate many cycles before get it right

Waterfall vs. Iterative

testing

Hats

Programming Teams

In the 1980s programmers developed the whole game (and did the art and sounds too!)

Now programmers write code to support designers and artists (content creators)

A Team Picture

Different Programs

Game code Anything related directly to the game

Game engine Any code that can be reused between

different games Tools

In house tools Plug-ins for off-the-shelf tools

Team Organization

Programmers often have a background in Computer Science or sciences

They usually specialize in some area (AI, graphics, networking) but know about all other areas

Teams usually have a lead programmer They sometimes have a lead for each of

the major areas

Skills and Personalities

Successful teams have a mix of personalities and skills: Experience vs. new ideas Methodical vs. visionary

But hard-working is always the key

Methodologies

A methodology describes the procedures followed during development to create a game

Every company has a methodology (way of doing things), even if they don't explicitly think about it

Methodologies: Code and Fix

Unfortunately very common Little or no planning Always reacting to events Poor quality and unreliability of finished

product “Crunch” time normal

Methodologies: Waterfall

Very well-defined steps in development Lots of planning ahead of time Great for creating a detailed milestone

schedule Doesn't react well to changes Game development is too unpredictable

for this approach

Methodologies: Iterative

Multiple development cycles during a single project Each delivering a new set of functionality

The game could ship at any moment Allows for planning but also for changes

Methodologies: Agile Methods

Deal with the unexpected Very short iterations

2-3 weeks Iterate based on feedback of what was learned

so far Very good visibility of state of game Difficult for publishers or even developers to

adopt because it's relatively new

Make Coding Easier

Version control Coding standards Automated build Code review Unit testing and acceptance testing

Version Control

Recommended to use for team project Version control is

Database with all the files and history. Only way to work properly with a team. Branching and merging can be very useful Used for source code as well as game assets

(text and binary) CVS is one of the most popular tool

Coding standards

Coding standards are Set of coding rules for the whole team to follow Improves readability and maintainability of the code Easier to work with other people's code They vary a lot from place to place

Some simple, some complex Get used to different styles

Sample standards can be found at: http://www.chris-lott.org/resources/cstyle/CppCodingStandard.html

Automated builds

Dedicated build server builds the game from scratch

Takes the source code and creates an executable

Also takes assets and builds them into game-specific format

Build must never break

Quality Control

Code reviews Knowing others will read the code will make coding

more carefully Another programmer reads over some code and

tries to find problems Sometimes done before code is committed to

version control Can be beneficial if done correctly

Follow coding standards, and put comments

Avoid Run-time Errors

Run-time errors are hardest to trace and have the biggest damage

Initialize variables, use tools (Visual .Net is good at this), check boundaries, etc.

Asserts and crashes Use asserts anytime the game could crash or something

could go very wrong An assert is a controlled crash in the debug version Much easier to debug and fix Happens right where the problem occurred Don't use them for things that a user could do

Open a non-existing file Press the wrong button

Testing

Unit tests With very large codebases, it's difficult to

make changes without breaking features Unit tests make sure nothing changes Test very small bits of functionality in

isolation Build them and run them frequently Good test harness is essential

Testing

Acceptance test (or functional tests) High level tests that exercise lots of

functionality They usually run the whole game checking

for specific features Having them automated means they can

run very frequently (with every build)

Bug Report and Trace

Bug database Keep a list of all bugs, a description, their

status, and priority Team uses it to know what to fix next Gives an idea of how far the game is from

shipping Doesn't prevent bugs, just helps fix them

more efficiently

Leveraging Existing Code

A lot of code that games use is the same It's a total waste of time to write it over

and over Instead, spend your time in what's going

to make your game unique Avoid Not Invented Here (NIH)

syndrome!

Leveraging Existing Code

Reuse code from previous project Easier in a large company if you have an

engine and tools group Use freeware code and tools

No support Make sure license allows it

Leveraging Existing Code

Middleware Companies provide with components used

in game development physics, animation, graphics, etc

Commercial game engines You can license the whole engine and tools

and a single package Good if you're doing exactly that type of

game

Platforms

PCs Includes Windows, Linux, and Macs Can have very powerful hardware Easier to patch and allow for user content Need to support a wide range of hardware

and drivers Games need to play nice with other

programs and the operating system

Platforms

Game consoles Current generation

PS2, Xbox, GameCube Fixed set of hardware – never changes Usually use custom APIs – not very mature They have very limited resources Currently much better sales than PC games

(although that changes over time)

Platforms

Handhelds and mobiles Extremely limited hardware (although

rapidly improving) Programming often done in lower-level

languages (C or even assembly) However, DS and PSP in C++

Much smaller projects, teams, and budgets Emerging market

Platforms

Browser and downloadable games Small games – mostly 2D Need to be downloaded quickly Run on the PC itself (on any browser

usually)

Platforms

Multiplatform development The closer the platforms, the easier the

development Use abstraction layers to hide platform-

specific code, especially for GUI Choice:

Target the minimum common denominator for platforms (easy, cheap)

Or do the best you can in each platform (more expensive and time consuming)

Languages

C/C++ Java Script: Flash, Python, LISP, etc. C# XNA for PC and Xbox

C++

C used to be the most popular language for games

Today, C++ is the language of choice for game development

C++: Strengths

Performance Control over low-level functionality (memory

management, etc) Can switch to assembly or C whenever

necessary Good interface with OS, hardware, and

other languages

C++: Strengths

High-level, object-oriented High-level language features are essential

for making today's complex games Has inheritance, polymorphism, templates,

and exceptions Strongly typed, so it has improved reliability

C++: Strengths

C Heritage C++ is the only high-level language that is

backwards-compatible with C Has APIs and compiler support in all

platforms Easier transition for experienced

programmers

C++: Strengths

Libraries STL (Standard Template Library)

Comprehensive set of standard libraries Boost: widely used library with wide variety

of functionality Many commercial C++ libraries also

available

C++: Weaknesses

Too low-level Still forces programmers to deal with low-

level issues Too error-prone Attention to low-level details is overkill for

high-level features or tools

C++: Weaknesses

Too complicated Because of its C heritage, C++ is very

complicated Long learning curve to become competent

with the language

C++: Weaknesses

Lacking features No reflection or introspection features No method of object serialization No native support for message passing

C++: Weaknesses

Slow iteration C++ is fully compiled into binary format

from source code Compiling large numbers of files is very

slow This will only become more of a problem as

games become more complex

C++: When to Use It?

When performance is crucial If your current code base is mostly C and C++ If you have a lot of in-house expertise in C++ Avoid using it for high-level code, such as tools

Java for Game Development

Why use Java? It's a high-level OO language that

simplifies many C++ features Adds several useful high-level features Easy to develop for multiple platforms

because of intermediate bytecode Good library support

Java for Game Development

Performance Has typically been Java's weak point Has improved in the last few years: still not

up to C++ level, but very close Uses Just-In-Time compiling and HotSpot

optimizations Now has high-performance libraries Also has access to native functionality

Java for Game Development

Platforms Well suited to downloadable and browser-

based games Dominates development on mobile and

handheld platforms Possible to use in full PC games

More likely to be embedded into a game Not currently used in consoles

Java in Game Development

Commercial games using Java Downloadable games like those from

PopCap Games: Mummy Maze, etc Online card games PC games using Java as a scripting

language: Vampire: The Masquerade, Star Wars Galaxies

PC games fully written in Java: You Don't Know Jack, Who Wants to Be a Millionaire

Scripting Languages

Why use scripting languages? Ease and speed of development Short iteration time Code becomes a game asset Offer additional features and are

customizable

Scripting Languages

Drawbacks Slow performance Limited tool support Dynamic typing makes it difficult to catch

errors Awkward interface with the rest of the game Difficult to implement well

Scripting Languages

Popular scripting languages Python Lua Other off-the-shelf options such as Ruby,

Perl, Javascript Custom scripting languages

UnrealScript, QuakeC, NWNScript

Scripting Languages

How to choose a scripting language Consider whether you need one at all What features do you need? What kind of performance do you need? What debugging facilities does the language

have? On what platforms does it need to run? What resources and expertise are available?