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GeoGebra and Joystick

Dr Đorđe Herceg, Dr Dragoslav HercegFaculty of SciencesUniversity of Novi SadSerbiaherceg@dmi.uns.ac.rs

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GeoGebra in Novi SadFaculty of Sciences, University of

Novi SadBesides regular work, members

of our faculty also teach in elementary and high schools

Many of our graduates work as matematics teachers in schools

We organize courses and meet our colleagues from schools

We use and recommend GeoGebra!

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GeoGebra institute of Novi Sad

GeoGebra Institue of Novi Sad, Serbia

http://sites.dmi.rs/gins/

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How we use GeoGebraGeoGebra is great for preparing

teaching and self-study materials.It is free, easy to download and

install and it speaks our language.We have developed tools for

numerical mathematicsAlso accompanying materials for

textbooksWe often find it easier to “sketch”

an explanation in GeoGebra, than on paper!

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What we would like to doLearning through playWe want to motivate children to learn

while playing mathematical games (more on that later)

We also want to provide a more direct way of manipulating geometrical drawings

Especially important with younger children that cannot grasp abstract notions

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The problem we address

Once prepared, interactive drawings need user input, which is provided by typing commands, moving sliders and clicking checkboxes.

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One parameter at a timeWe can only control one

parameter at a time with the mouse

Sliders and checkboxes on the screen are just imitations of the “real thing”

Precise “aiming” at sliders and checkboxes can be problematic, particularly during talks and demonstrations

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What we have is:

MOUSE

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What we want is:

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Joysticks and GamepadsThey can have up to 6 axesMany buttons (typically 6-12)POV hatsAll of these can be used

simultaneously!

Gamepad

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Why use game controllers?

Benefits:◦Control many parameters

simultaneously◦Inexpensive◦Ubiquitous◦Intuitive – “I push here and that thing

moves”◦Designed to be used without looking

(tactile feedback)◦Interesting for the kids

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Drawbacks?Not very preciseNot everybody has oneSupport for game controllers on

various platforms and operating systems is not standardized

There exist several SDKs for game controllers:◦DirectX (Windows, unmanaged code)◦SlimDX (Windows+.NET)◦JXInput (Java+JNI)◦...

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GameControllerInput (GCI)Developed in C# on .NETUses the SlimDX library to access

DirectInput/DirectX compatible game controllers

Hosts GeoGebra applets inside a WebBrowser component

Extendable – easy to add new mappers

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GeoGebra applet methodsIn version 3.2, GeoGebra

JavaScript interface provides many useful methods which provide full control over the drawings.

Our program acts as a “shell” around the GeoGebra applet, which interprets input given by a game controller and maps it to parameters and object properties in a drawing.

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Axis mappingRaw data obtained from a

joystick axis is in range [0,65535]It can be mapped linearly to any

given interval [a, b]However, game controllers are

not precision devices. “Dead zone” must be set appropriately.

Should the joystick axis map directly to a variable, or should it control the amount of change?

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Mapping curve for axes

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Button mappingEach button can be mapped to a

command, such as:◦Set a value of a variable◦Change a value of a variable (+/-)◦Control visibility of objects◦Control trace of objects◦Refresh display◦Generate random numbers◦etc...

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How it works

Game controller

AxisMapperButtonMapp

erJavaScript GeoGebra

Input from a game controller is passed to various mappers

Mappers call JavaScript methodsJavaScript methods call methods of an

embedded GeoGebra applet

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ConfigurationUpon application start, the user

assigns various mappers to game controller’s axes and buttons.

A configuration is a set of all mappings for a game controller.

Configurations can be saved and loaded from files.

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Screenshots 1/2

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Screenshots 2/2

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DEMO

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ConclusionsChildren like to experiment, especially

with something they can touchThanks to a growing list of GeoGebra

applet methods, it is now possible to have almost complete control of GeoGebra from the outside

When interpreted appropriately, input from gamepads and joysticks can be used to control drawings in GeoGebra

So we can provide a more intuitive and less artificial way of interaction with drawings

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Thank you!