Slideshow from Aydin Akcasu's presentation on programming a Leap Motion controller at CodeMash 2014.

1. Aydin Akcasu
Senior Software Architect
Interactive Business Systems, Inc.

2. Who am I?
 Aydin has been writing software for close to 30 years. He has
provided inventive solutions using technologies such as
Java, JavaScript, ASP, Visual Basic, VB.Net, C#.Net, ASP.Net, Flash.
 He has given presentations and classes in the past to local groups
(as well as in India) in topics such as "KPL-Kids Programming
Language", ‘Help, I need to learn Javascript’, ‘Cover you ASP’, ‘VBWhat is it good for?’,
 ‘FLASH-in-the-Pants?’, ‘C#, ASP.Net on a Budget’, ‘Introduction to
‘C#.Net’, ‘AJAX – A What’, ‘Google Maps APIWheres’Waldo?’, "Cross-Platform Mobile Development". He also
created course content and taught at Washtenaw Community
College (C#.Net, Advanced C#.Net), for many years.

3. Who are we?
Interactive Business Systems
200+ Consultants in U.S.
4 Business Units and
2 Development Centers
Strategic Staffing Solutions
Application & Infrastructure
Custom Solutions
U.S. Headquarters,
Oak Brook, Illinois

4. Intro Videos

5. Evolution of Input Devices

6. The Leap Motion Controller
 Description:
• With just your hands and fingers in the air – swipe, pinch, wave, and grab for just
 The Leap Motion Controller tracks both hands and all 10 fingers with
pinpoint precision and incredible speed. That wide-open space
between you and your computer is now yours—to play, create and
explore. Reach into another world without actually touching anything.
 Website:
 https://www.leapmotion.com/
 Cost:
 $79.99.
 Buy:
 Best Buy or Online
 Applications:
 More than 150 free and paid apps in Airspace, the Leap Motion App
Store.
 https://airspace.leapmotion.com/

7. Architecture:
 Application Programming Interfaces
 The Leap Motion SDK provides two
varieties of API to get tracking data
from the Leap Motion service:
 a native interface and a
 The native interface is a dynamic library
that you can use to create new, Leapenabled applications.
• WebSocket interface.

The WebSocket interface and JavaScript
client library allow you to create Leapenabled web applications.

8. Programming Language Support
 The Leap Motion library is written in C++.
 Support for:

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


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C++
Objective-C
C#
Java
Python
JavaScript
Other Languages

9. LeapMotion Overview
 The Leap detects and tracks hands, fingers and finger-
like tools.
 The Leap software analyzes the objects observed in the
device field of view. It recognizes hands, fingers, and
tools, reporting both discrete positions, gestures, and
motion.

10. Field of View
 The Leap field of view is an inverted pyramid centered
on the device.
 The effective range of the Leap extends from
approximately 25 to 600 millimeters above the device
(1 inch to 2 feet).

11. The Coordinate System.
• The Leap right-handed coordinate system.

12. Motion tracking data Overview
 1. Frames
• 1.1. Lists of tracking data
• 1.2. Frame motion
 2. Hand model
• 2.1. Hand attributes
• 2.2. Hand motion
• 2.3. Finger and Tool lists
• 3. Finger and Tool models
 4. Gestures
• 4.1. Circle
• 4.2. Swipe
• 4.3. Taps
• 4.3.1. Key Taps
• 4.3.2. Screen Taps

13. 1. Frames
 A Frame object describes the overall motion observed in the Leap
field of view. It provides lists of:
 the tracking data
 gestures
 factors

14. 1.1.
Lists of tracking data
 Hands
 All hands.
 Pointables
 All fingers and tools as Pointable objects.
 Fingers
 All the fingers.
 Tools
 All the tools.
 Gestures
 All the gestures that started, ended, or which had an update.

15. 1.2. Frame motion
 rotationAxis
 A direction vector expressing the axis of rotation.
 rotationAngle
 The angle of rotation clockwise around the rotation axis (using the right-
hand rule).
 rotationMatrix
 A transform matrix expressing the rotation.
 scaleFactor
 A factor expressing expansion or contraction.
 translation
 A vector expressing the linear movement.

16. 2. Hand model
 The hand model provides information about the:
 position
 characteristics
 movement of a detected hand
 lists of the fingers
 tools associated with the hand

17. 2.1. Hand attribute
The Hand object provides several attributes reporting the physical characteristics
of a detected hand:
 palmPosition
 The center of the palm measured in millimeters from the Leap origin.
 palmVelocity
 The speed of the palm in millimeters per second.
 palmNormal
 A vector perpendicular to the plane formed by the palm of the hand. The vector points
downward out of the palm.
 direction
 A vector pointing from the center of the palm toward the fingers.
 sphereCenter
 The center of a sphere fit to the curvature of the hand (as if it were holding a ball).
 sphereRadius
 The radius of a sphere fit to the curvature of the hand. The radius changes with the shape
of the hand.

18. 2.1.1. The
Normal Vector
• The direction and palmNormal are unit direction vectors describing
the orientation of the hand with respect to the Leap coordinate
system.
• The normal vector points perpendicularly out of the hand; the
direction vector points forward.

19. 2.1.2. Sphere
Size
 The sphereCenter and sphereRadius describe a sphere that is
placed and sized to fit into the curvature of the hand:

20. 2.2. Hand motion
 The Hand object also provides several attributes reporting the motion of a
detected hand between frames. The Leap analyzes the motion of the
hand, as well as its associated fingers and tools and reports representative
translation, rotation, and scale factors.
 The attributes describing the synthesized motion include:
 rotationAxis
 A direction vector expressing the axis of rotation.
 rotationAngle
 The angle of rotation clockwise around the rotation axis (using the right-hand rule).
 rotationMatrix
 A transform matrix expressing the rotation.
 scaleFactor
 A factor expressing expansion or contraction.
 translation
 A vector expressing the linear movement.

21. 2.3. Finger and Tool lists
 You can access the fingers and tools associated with a hand using
one of three lists:
 Pointables
 Both fingers and tools as Pointable objects.
 Fingers
 Just the fingers.
 Tools
 Just the tools.

22. 3. Finger and Tool models
 The Leap detects and tracks both fingers and tools within its field of
view. The Leap classifies finger-like objects according to shape. A tool is
longer, thinner, and straighter than a finger.
 The physical characteristics of pointable objects include:
 length
 The length of the visible portion of the object (from where it extends out of the hand to
the tip).
 width
 The average width of the visible portion of the object.
 direction
 A unit direction vector pointing in the same direction as the object (i.e. from base to tip).
 tipPosition
 The position of the tip in millimeters from the Leap origin.
 tipVelocity
 The speed of the tip in millimeters per second.

23. 4. Gestures
 The Leap recognizes certain movement patterns as gestures which could
indicate a user intent or command. For each gesture observed, the Leap
adds a Gesture object to the frame.
• You can get these Gesture objects from the Frame gestures list:
 Circle
 A single finger tracing a circle.
 Swipe
 A linear movement of the hand.
 Key Tap
 A tapping movement by a finger as if tapping a keyboard key.
 Screen Tap
 A tapping movement by the finger as if tapping a vertical computer screen.

24. 4.1. Circle
 You can make a circle with any finger or tool. Circle gestures are
continuous. Once the gesture starts, the Leap will update the
progress until the gesture ends. A circle gesture ends when the
circling finger or tool departs from the circle locus or moves too
slow.
 A circle gesture with the forefinger.

25. 4.2. Swipe
 The Leap recognizes a linear movement of a finger as
a Swipe gesture.
 A horizontal swipe gesture.

26. 4.3. Taps
• The Leap recognizes two types of taps:
• the downward Key Tap
• the forward Screen Tap.

27. 4.3.1. Key Taps
 The Leap recognizes a quick, downward tapping movement by a
finger or tool as a Key Tap gesture.
 You can make a key tap gesture by tapping downward as if pressing
a piano key. Tap gestures are discrete. Only a single Gesture object is
added per tap gesture.
• A key tap gesture with the forefinger.

28. 4.3.2. Screen Taps
 The Leap recognizes a quick, forward tapping movement by a finger
or tool as a Screen Tap gesture.
 You can make a key tap gesture by tapping or pushing foward in
space as if touching a vertical touch screen. Tap gestures are
discrete. Only a single Gesture object is added per tap gesture.
 A screen tap gesture with the forefinger.

29. For More Information:
 Me:
 Aydin Akcasu
 Aakcasu@ibs.com
 @Aakcasu
• Leap Motion
• https://www.leapmotion.com/
• https://developer.leapmotion.com/
• https://developer.leapmotion.com/documentation/Languages/JavaScript/G
uides/Leap_Overview.html

30. Questions