In this course concepts and requirements of the video game development will be taught. Students will get familiar to the fundamentals of the game industry and finally put all the learned stuff together to work on a small game project.

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In The Name Of God
Video Game Development
Amin Babadi
Department of Electrical and Computer Engineering
Isfahan University of Technology
Spring 2015
User Input

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Outline
 The keyboard
 Mouse
 Joysticks
 Hardware abstraction
 Force feedback

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User Input
 A smooth user interaction model is key to any good game.
 Sadly, there will be few general rules.
 User interaction takes place at a relatively low abstraction
level, and implementations tend to be quite hardware
dependent.

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The Keyboard
 Keyboards are the main input device for PC-based games, but
are also available for mobile phones, some consoles, and palm
devices.
 The most widely available input device!
 Unfortunately, such a popular input device is not very well
suited for games.

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The Keyboard
 For gaming purposes, two types of routines for reading
keyboards are relevant.
1. Synchronous routines
2. Asynchronous routines

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1. Synchronous Routines
 Synchronous routines wait until a key is pressed and then
report it to the application.
 Synchronous read modes are used to type information, such
as the character name.
 But they are not very well suited for real gameplay (why?).

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2. Asynchronous Routines
 Asynchronous routines return immediately after being called,
and give the application information about which keys were
pressed, if any.
 Asynchronous controllers are the way to go!
 They provide fast tests to check the keyboard state efficiently.

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2. Asynchronous Routines
 Asynchronous routines can also belong to two different
families.
o Some of them are designed to test the state of individual keys (how?).
o Others retrieve the whole keyboard state in a single call.
 What are pros/cons of these 2 sub-types?
 Which sub-type is generally more efficient? Why?

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Mouse
 Mice are especially popular in PC games, but game consoles
do not usually support them.
 Unlike a keyboard or joystick, a mouse not only generates
button or key presses, but 2D positions as well.
 The operation of the mouse can be divided into transmitting
positional information and sending button press and release
messages.

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Mouselook
 A popular use of the mouse is to implement the classic
mouselook used in many first-person shooters.
 All we have to do is use the keys to change our position, and
use the mouse to reorient our viewpoint.
Killzone 3

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Joysticks
 The joystick was introduced in the 1970s as a way to
represent positional data easily.
 The first models were restricted to binary tests.
 Today, all joysticks map the sticks' inclination to a continuous
range of values, so we can control our characters precisely.
 Controlling a joystick is slightly more complex than working
with a keyboard or a mouse (why?).

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Response Curves
 For example, imagine a game like Mario, where there is no
speed control: Mario is simply running left, running right, or
standing still.
 Assume that the analog output is in the range −100,100 .
 So how do we implement that using an analog controller?
 We need to define a transfer function.

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Response Curves
Response curve without (left) and with (right) a dead zone.

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Response Curves
Types of response curves.

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Hardware Abstraction
 Games that run on platforms that support a variety of input
controllers offer the richest gaming experience.

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Hardware Abstraction
 There are two paths a developer might follow when coding for
such a platform:
o Some games will choose to use one (and only one) of the existing
controllers.
o Some other games will let the user choose the input method he or
she wants to employ.
 Hardware abstraction means coding your game with a
"virtual" controller in mind, so any controller that conforms to
that abstract profile can be fitted into the code with zero
impact on the game engine.

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Hardware Abstraction
A possible class structure to implement device abstraction.

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Force Feedback
 Many input controllers come with some sort of force feedback
these days.
 Force feedback hardware simulates vibration and other force-
based effects by incorporating one or more motors that can
be configured via programming.
 Sadly, these techniques are largely platform dependent.

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Force Feedback
Microsoft's Force Editor, built into the DirectX SDK.

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