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Initial comparison of two important gesture input systems i.e. Leap Motion Controller and Microsoft Kinect.
Leap Motion Controller:
Tracking Capability: Objects: The Leap Motion software uses an internal model of a human hand to provide predictive tracking even when parts of a hand are not visible and it can track three things. • Hands: Provides information about the identity, position, and other characteristics of a detected hand. • Fingers: Provides information about each finger on a hand. • Finger-‐like tools: Only thin, cylindrical objects are tracked as tools. Motions: Motions are estimates of the basic types of movements inherent in the change of a user’s hands over a period of time. This includes • Translate: Average change of positions of an object or objects in the scene. • Scale: Motion towards or away from each other. • Rotate: differential movement of objects within the scene Gestures: The Leap Motion software recognizes certain movement patterns as gestures, which could indicate a user intent or command. Currently it supports below three types of gestures • Circle: A finger tracing a circle. • Swipe: A long, linear movement of a hand and its fingers. • Tap: A tapping movement by a finger. Distance Range: Effective range of device is 25 to 600 millimeters above the device (1 inch to 2 feet), which makes it perfect for close PC interaction [3]. Hardware: Its uses stereovision principle to identify fingers, hands and gestures using optical trackers and it consists of • Three separate IR LED emitters • Two IR Cameras
Accuracy: • The controller accuracy drops with the distance (radius) and when the tracking objects are to the far left or far right [1]. • Significant drop in accuracy for the samples taken more than 250 mm above the controller [1]. But it is 100x more accurate than anything available on the market and have 1/100th mm-‐ tip of pin accuracy [2]. Web-‐Integration: Inbuilt JavaScript API, which has Support for most modern browsers and also highly optimized for rendering. • leap.js available from http://js.leapmotion.com/ Advantage over Microsoft Kinect: • The strength of the Leap Motion controller is the accurate level of detail provided by the Leap Motion API. The API provides access to detection data through a direct mapping to hands and fingers.
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This contrasts with Microsoft Kinect - where sensory data is returned in a raw format, which must then be cleaned up and interpreted. The benefit of strong API preprocessing is that error reduction can be abstracted away from client applications meaning client applications can be built faster and with consistently accurate data [4]. More than 30K web-based apps. It has got strong presence on web and reason behind this is simple i.e. SDK support for multiple platforms. Small and portable, Low Z height, low CPU and power consumption. It is compatible with both USB 2.0 as well as USB 3.0 where as Kinect is compatible with USB 3.0, and doesn’t support most USB over Ethernet extenders, which makes it complicated.
Microsoft Kinect:
Tracking Capabilities: Kinect is a sensor used especially for gaming, that too with a gaming console. Microsoft did release a windows version of it but considering it's capabilities, Gaming and Fitness are the most appropriate areas where Kinect would fit. Skeleton Tracking: • Can track up to 6 skeletons with 25 joints each, including joint orientation and finger tracking. • Applications can also track the positions of user’s joints (head, shoulders, hips, hands, etc.) in space. Face Tracking: • Various attributes of the user’s face can be tracked, including the relative positions of lips and eyebrows, which can be interpreted as facial expressions. Multiple Sensors: • It also allows tracking IR reflective objects, while filtering out IR lights. • Wider view of space to track objects closer to the cameras. Voice Control: • Can detect open and closed hands as well as two-‐finger lasso gesture. • A larger field of view allows the sensor Distance Range: Kinect is perfect for the mid or long range distance. • 850 mm to 4000 mm range (normal Mode) • 400 mm to 3000 mm range (near mode) Hardware: • 3D Depth Sensors • RGB Camera • Multi Array MIC • Motorized Tilt Accuracy: • The Kinect cannot easily distinguish individual fingers on a hand, which means gestures tend to involve more gross movements than simple pointing. • Up to six users can be recognized in the field of view of the sensor but only two users can be tracked in detail.
Web Integration: • The SDK and driver are only available for Windows 8. • Not all the features are available on the open source toolkits for development like OpenNI framework [6]. Advantages over leap: • Audio Channel: Can be used as microphone as well as for speech recognition for e.g. Multimodal feedback “OK”, “YES” etc. • The Kinect SDK provides access to the raw depth data from the sensor, as well as images from the IR and RGB cameras and developer can use this accordingly. • Full body tracking * There are lots of new features and API will be coming with the new version like Visual Gesture Builder, which will use machine learning and body frame date to define a gesture.
Final Verdict:
According to our use case we are trying use those input devices, which can enable students to express and interact with their hands. Furthermore we are looking for the device, which have extensive support on the web. In both case leap motion controller wins.
References: [1] An Analysis of the Precision and Reliability of the Leap Motion Sensor and Its Suitability for Static and Dynamic Tracking by Jože Guna *, Grega Jakus, Matevž Pogačnik, Sašo Tomažič and Jaka Sodnik, Sensors ISSN 2014 [2] About the product https://www.leapmotion.com/product [3] API Documentation Reference https://developer.leapmotion.com [4] The Leap Motion controller: A view on sign language by L Potter, J Araullo, L Carter ACM 2013. [5] Beginning Kinect Programming with the Microsoft Kinect SDK, by J Webb & J Ashely, Book published 2012. [6] Integrating Motion Tracking Sensors to Human-‐Computer Interaction with Respect to Specific User Needs, M Vinkler CESCG 2014.
