Leap Motion Development Essentials

Table of Contents

Leap Motion Development Essentials

Credits

About the Author

About the Reviewers

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Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. Leap Motion SDK – A Quick Start

An overview of the SDK

Quick start

Major SDK components

Controller

Config

Screen

Math

Frame

Hand

Pointable

Finger positioning

An example of cursor control

A gesture-triggered action

Summary

2. Real Talk – Real Time

A simple gesture recognizer

Using the MIDI output

Blocking and latency

Multiprocessing with threads

Refactoring for multithreading

The producer-consumer race condition

Summary

3. Actual Gestures

Computer input

Natural gestures

Receiving gestures

WindowFlinger – a high-level gesture application

Window management abstraction

Window docking

Driver implementation – Mac OS X

Accessibility API

flinger::MacDriver

Summary

4. Leap and the Web

HTML5 and Leap

WebSocket

The Leap Motion service

LeapJS

JavaScript visualization

Summary

5. HTML5 Antics in 3D

Cross-platform graphics party

WebGL

Three.js + LeapJS – the awesomesauce

Animating rotation

Summary

Index

Leap Motion Development Essentials

Leap Motion Development Essentials

Copyright © 2013 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: October 2013

Production Reference: 1211013

Published by Packt Publishing Ltd.

Livery Place

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Birmingham B3 2PB, UK.

ISBN 978-1-84969-772-9

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Cover Image by Suresh Mogre (<[email protected]>)

Credits

Author

Mischa Spiegelmock

Reviewers

Shaun Walker

Carlos Zinato

Acquisition Editors

Erol Staveley

Rebecca Youe

Commissioning Editor

Mohammed Fahad

Technical Editors

Vrinda Nitesh Bhosale

Pratik More

Amit Ramadas

Project Coordinator

Suraj Bist

Proofreader

Bernadette Watkins

Indexer

Hemangini Bari

Production Coordinator

Manu Joseph

Cover Work

Manu Joseph

About the Author

Mischa Spiegelmock is an accomplished software engineer from the San Francisco Bay Area. Slightly infamous from light-hearted technical pranks from his youth, he is now a respectable CTO at a healthcare software startup. His passions are architecting elegant and useful programs and sharing his insights into software design with others in a straightforward and entertaining fashion.

This book would not exist without the extremely passionate people at Leap Motion, whose vision and heroic efforts to improve the interactions between humans and computers should be commended. Special mention to Elizabeth Ruscitto for taking the time to provide me with informative answers to my queries. I would also like to thank Hep Svadja Hepic Photography, for the amazing pictures.

About the Reviewers

Shaun Walker is a software and web developer from Tasmania, Australia. He enjoys tinkering with electronics, listening to music, playing computer games, and working on small projects that generally never get finished.

Shaun has a Bachelor's degree in Computing, majoring in Human Interface Technology, part of the HITLab, an International collaboration effort between a few universities around the world. His areas of focus during his studies were in augmented reality, virtual reality, and gesture-based interactions.

With a history in corporate IT support, working on network integration, software and web development, his main employment is with a Brisbane-based medical start-up.

Ramblings by Shaun can be found at his blog at http://theshaun.com or on Twitter @theshaun.

Carlos Zinato, aged 25, is from São Paulo, Brazil. Currently, he's living in Miami Beach, FL, developing mobile apps and games, playing bass guitar, and getting to know people and places.

Working with tools such as Objective-C, Leap Motion, Titanium, and Unity3D, Carlos makes mobile apps and games and this is what he loves to do.

Carlos is currently aiming to keep making awesome apps and games with skilled friends and teams. He not only cares about the money but, more importantly, about the knowledge. Carlos wants to keep working with brilliant people that enhance his job, his life, and his pocket.

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Preface

Once in a great while, a revolutionary and exciting new way of interacting with technology comes along. Leap Motion makes natural gesture-based interfaces a reality, and gives software developers access to a large and powerful set of features and capabilities. This guide is for software engineers who wish to get an overview of the Leap Software Development Kit modules, types and interfaces in C++ along with some guidelines for getting the most out of your Leap device and creating usable, gestural software interfaces.

What this book covers

Chapter 1, Leap Motion SDK – A Quick Start, explores how to begin using the Leap C++ SDK right away, with a sample mouse control program. It covers how to receive frame updates and read finger position data.

Chapter 2, Real Talk – Real Time, guides you through writing a multithreaded MIDI controller, which uses a blocking OS call without sacrificing responsiveness.

Chapter 3, Actual Gestures, covers a high-level discussion of gesture interfaces and a look at the available Leap SDK recognizers. It also covers creating an interface to manipulate Windows OS.

Chapter 4, Leap and the Web, teaches you how to create Leap-enabled web pages, using JavaScript with the LeapJS library, with no additional installation or configuration.

Chapter 5, HTML5 Antics in 3D, combines LeapJS, WebGL, and Three.js together to manipulate objects in 3D space in a web page using Leap Motion.

What you need for this book

You will need a working knowledge of basic C++ and a compiler. Additional demonstration operating system-specific code is provided for Mac OS X APIs, but neither OS X nor familiarity with it is a requirement. An understanding of basic geometry and concepts such as vectors is useful for spatial manipulations.

Who this book is for

This book is for developers with an interest in using the Leap Motion input device with their software. This book gives a broad overview of most of the available functionality in the Leap SDK, which can be transferred to any of the supported language interfaces, as the data types and routines are nearly identical.

Conventions

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

Code words in text are shown as follows: We can include other contexts through the use of the include directive.

A block of code is set as follows:

    if (frame.hands().empty()) return;

    const Leap::Hand firstHand = frame.hands()[0];

    const Leap::FingerList fingers = firstHand.fingers();

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

namespace leapmidi {   

typedef double

midi_control_value_raw

;

typedef unsigned short

midi_control_value;

New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes, for example, appear in the text like this: Prepare to be astounded when you point at the middle of your screen and the transfixing message, You are pointing at (0.519522, 0.483496, 0), is revealed.

Note

Warnings or important notes appear in a box like this.

Tip

Tips and