06. Game Architecture

Video Game Development: Game ArchitectureA. Babadi 1 of 52
In The Name Of God
Video Game Development
Amin Babadi
Department of Electrical and Computer Engineering
Isfahan University of Technology
Spring 2015
Game Architecture

Outline
 Real-time applications
 Game loop
o Updating
o Rendering
 Updating the player and the world
 Rendering and level of detail
 Game loop in networked games
 Preproduction
 Production
 Maintenance
o What is a mod?

Real-Time Software
 Video games are real-time software applications.
 The arrival of input information is highly unpredictable.
 The application must process and respond to the input
accordingly.
 This time-dependent information must then be displayed on a
screen.

An Example
 Consider a software application designed to aid in air traffic
control.
 Internals of this system consist of
o A data acquisition module,
o A display/computation module, and
o An interaction module.
Air traffic controller

 All real-time interactive applications consist of 3 tasks running
concurrently.
Real-Time Loops
World
Simulation
User Input
Resulting State
Presentation

Game Loop
 In a game, both the world simulation and the user input can
be considered tasks belonging to the same global behavior,
which is "updating" the world.
Updating Rendering

Game Loop
𝑙𝑜𝑛𝑔 𝑙𝑎𝑠𝑡𝑇𝑖𝑚𝑒 = 𝐺𝑒𝑡𝑇𝑖𝑚𝑒();
𝑤𝑕𝑖𝑙𝑒 (! 𝑒𝑛𝑑)
*
𝑖𝑓 ((𝐺𝑒𝑡𝑇𝑖𝑚𝑒() − 𝑙𝑎𝑠𝑡𝑇𝑖𝑚𝑒) > 1000/𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦)
*
𝑔𝑎𝑚𝑒_𝑙𝑜𝑔𝑖𝑐();
𝑙𝑎𝑠𝑡𝑇𝑖𝑚𝑒 = 𝐺𝑒𝑡𝑇𝑖𝑚𝑒();
+
𝑝𝑟𝑒𝑠𝑒𝑛𝑡𝑎𝑡𝑖𝑜𝑛();
+

Game Loop
 Game loop should at least be executed 25 times per second.
 What if frames-per-second (FPS) rate varies?
 Are there any alternatives?

1. Updating
 We can divide updating block into 2 main blocks.
Updating the Player
Updating the World

1.1. Updating the Player
 We need an updated snapshot of the player state in each
frame.
Getting the Input from Player
Restricting Player Interactions
Player Update

 How do the input devices work?
 What factors usually restrict the player interactions?
 Which step is the hardest one?

o Abstract device controllers (more in the next lectures)

o Geometric and logical restrictions

o Restricting player interactions is usually the hardest step.

o Restricting player interactions is usually the hardest step.
 Can we apply these rules to games like Tetris?

1.2. Updating the World
 In addition to the player's action, the world keeps its own
agenda.
 Which one is more important? The player or the world?
 How can we process the whole world?

 How can we subcategorize active and passive elements?
Game World Entities
Active Entities Passive Entities

 How can we deal with these entities?
Game World Entities
Active Entities
Logical Entities AI Entities
Passive Entities

Passive Entities
 These items play a key role in the player restriction section,
but are not very important for the sake of world updating!
 In games with large worlds, we can pre-select a subset of
passive entities so that player restriction portion can only
focus on those entities.
 But the majority of time in the world update section is spent
checking the other type of entities.

Active Entities
Sort According to Relevance
Update State
Sort According to Relevance
Sense Internal State and Goals
Sense Restrictions
Decision Engine
Update State
Logical entities
AI entities

2. Rendering
 Usually any world-rendering pipeline will consist of 2 parts.
Selecting the Relevant Subset
Actual Rendering
We’ve already covered this subject in
“The Rendering Pipeline” lecture.

2.1. Selection
 We only want to draw parts of the game world that are visible
from the player’s viewpoint.
 Sometimes level of detail (LOD) technique is used too.
 What are the differences between the player character and
other objects in the rendering step?

Level of Detail (LOD)

Getting the
Input from
Player
Restricting
Player
Interactions
Player Update
Sort According
to Relevance
Update State
Sort According
to Relevance
Sense Internal
State and
Goals
Sense
Restrictions
Decision
Engine
Update State
Selecting the
Relevant
Subset
Actual
Rendering
A Quick Overview

Game Loop in Networked Games
 So far, we’ve only focused on single-player games.
 Is the described model suitable for networked games too?
 How are player and non-playable characters defined in a
networked game?

Game Loop in Networked Games
 The player update section must change to make sure every
player update is followed by a broadcast message that sends
the newly computed position to other gamers through the
network.
 AI section needs a special-case AI module that receives data
from the communications channel and reflects it to the local
gaming environment.

The Programming Process
 We will now focus on today's production techniques and how
programming must be planned to ensure timely and complete
delivery.
 Any modern game requires hundreds or thousands of source
files and several hundred thousand lines of code.
 Game programming is a very complex task!

Development Stages
 All game projects consist of three basic stages.
Preproduction
Production
Maintenance

1. Preproduction
 The concept of the game is agreed upon.
 Different technologies and solutions are evaluated.
 Gameplay formulae are tested.
 Some early concept art is created.
 The result is a working prototype of the game.
 The game design should be final.

1. Preproduction
 It’s the only phase where a game company should be allowed
to experiment.
o It is a highly experimental phase!
 The role of preproduction is, then, to analyze alternatives and
finally create a detailed plan.
o Technology is always seen as a potential risk!
 Technology prototypes usually focus more on showcasing the
key elements of the gameplay.
o The presentation layer is kept in a very early and crude form.

Where Do Ideas Come From?
 Most promising game projects start with a raw game design.
 This is usually expressed in a single sentence that defines the
genre and gameplay as well as your role in the story.
 "The game is a first-person shooter, with some outdoors areas
and large monsters, where you are a warrior trying to save the
princess."

Where Do Ideas Come From?
 Your initial sentence must answer:
o Who is the player?
o What are his goals?
o What's the genre?
o How does the game play?

Alternative Paths
 Sometimes, games start with a strong narrative description.
o "You are a scientist in a military complex full of soldiers who are trying
to conquer the world.“
 Another game type is started because of some unique and
impressive technology.
o "let's build a game with this brand new outdoors renderer.“
 Starting with the gameplay is a much safer bet.

Discussing Feature Sets
 Lead programmer should at first define a list of features to be
implemented into the game, e.g.
o How many characters should be displayed?
o Will the user be able to pick objects?
 This list should be crafted as a team effort between the design
and the coding team.
 A good way of getting a reasonable feature set laid out on
paper is to use an expansion-contraction process.

Expansion-Contraction Process
Create an Exhaustive List
Clustering Features
Choosing Best Features

Minimax Method
 A good, objective way to choose which clusters to implement
is to use the classic minimax method.
 Minimax tries to minimize disadvantages and maximize
advantages.
 This is usually depicted in a 2D matrix of cost versus benefit.

Minimax Matrix
Worst
Solution
Best
Solution
Cost
Importance

Minimin Features
Cost
Importance
• Mainly decorative elements
• Should be coded at the very
end of the project if time
allows.
• A good example is birds
flying by in a 3D adventure.

Maximin Features
Cost
Importance
• These features should be
dropped immediately.
• As an example, imagine a car
racing game where you can
see the driver inside the car.

Minimax Features
Cost
Importance
• Obviously, these should all
be built into the game,
assuming time allows for
them.
• Being able to configure your
character's look in a role-
playing game and AI
communication are two good
examples.

Maximax Features
Cost
Importance
• An outdoors renderer for a
flight simulator is a good
example.
• Is there an easier
implementation?
• Is your team capable of
handling the feature?
• Select some maximax
features and forget about
the rest.

2. Production
 After completing preproduction and securing funding for the
game, production begins.
 It’s the longest part of the process and usually takes between
one and three years to complete.
 Production is often divided into milestones.

2. Production
 The game takes shape following the planning that has been
laid out during preproduction.
 The technology prototype built during preproduction will also
mutate to implement all the final features the game needs.
 Production is usually where all the eye candy is put in place,
and games show their full technological complexity.
 Art assets are created in a factory-like fashion, game levels are
crafted, and so on.

2. Production
 At the end of this iterative process, a final version of the game
must be delivered to the publisher.
 This process ensures that the game is virtually bug-free and
also reaches the desired quality standard.
 In the case of console games, this process is a bit more
complex than for a PC title!

Agile Methodology
 One method employed for game development is agile
development.

Milestones Are King
 More is not better!
 "On time" is better than "more ambitious.“
 Surgical teams and key members are a risk.
 Don’t forget the order of execution!

3. Maintenance
 Games usually have a relatively short shelf life.
 Support must be provided: patches, editing tools for the fan
community, and additional missions.
 Maintenance is the moment when relationships with
consumers are at their highest point.
 Games with good maintenance have longer shelf lives.
 What about massively networked games?

Some Ideas
 Release new content for the game.
o Extra missions or characters are easy to do.
o These contents can be placed on web sites for easy deployment.
o Remember that a good data-driven design is the key to success.
 Provide users with content creation tools.
o A mod community can be started.
o Content sharing should not be seen as a potential problem but as an
opportunity to increase your user base.
o Many teams have hired personnel directly from the mod community
because they were the most talented users of the editing toolset.

Mod
 A mod or modification is the alteration of the a video game in
order to make it operate in a manner different to its original
version.
An example of game modification in GTA: Vice City (2002)

Maintenance of Massively Multiplayer Games
 Massively multiplayer games are a completely different
business when it comes to maintenance (or should we say
product development?!).
 These games are actually created in the maintenance phase!
 Because they are pay-per-play titles, keeping new content
pouring in is the best (and only) way to make the game
profitable.

There Is More Maintenance!
 The maintenance phase is a great time to organize, archive,
and document.
 Developers forget good coding practices during lengthy
crunch times.
 Some maintenance time should go into revising your code,
and storing and documenting the reusable modules.
 There's no deadline pressure on the maintenance phase.

References
 Sanchez-Crespo’s textbook,
 Wikipedia, and
 Some other sources on the Internet.

06. Game Architecture

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