An Augmented Reality Exhibition Guide for the Iphone
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An Augmented Reality Exhibition Guide for the iPhone Mohamed Ashraf Nassar, Fatma Meawad German University in Cairo [email protected], [email protected] Abstract background that supports our subsequent design decisions. With a clear description of the system Handheld Augmented Reality (AR) can enable requirements and its essential success criteria, we intuitive browsing and annotation of objects in an discuss a simple scenario on a prototype of our exhibition through the visitors’ in-hand mobile proposed design. Based on some experimental results devices. Several researchers explored Handheld AR of testing the prototype in different scenarios, we technologies in museums and exhibition-like highlight some future directions for this on-going environments. However, despite the proliferation of work. smart phones that can act as magic lenses for augmented objects, AR technologies are not widely 2. Tracking Techniques adopted in exhibitions. This paper investigates the possible techniques to build a reliable, scalable and Choosing a tracking technique for an Augmented cost effective solution for an indoor marker based Reality application is an important design decision. exhibition guide on the iPhone. After reviewing Such choice can either cause or resolve many possible tracking technologies, available open challenges for the application. For example, reliable source marker based tracking toolkits on the iPhone and accurate solutions might come with a are explored. The paper concludes with a proposed compromise of usability and performance. design for dynamic content creation to augment and Additionally, using a free tracking toolkit, annotate exhibition objects. purchasing one or building one from scratch would impact reliability, performance and the expected cost 1. Introduction of the whole solution. We aim to present a solution that combines the benefits of usability, reliability and Augmented reality has become a rich field of cost effectiveness, in order to achieve wide adoption. research in recent years, so have the technologies In this section, we give an overview of existing enabling it to become widely used. Smart phones, for tracking techniques and their suitability for our main example, with their growing capabilities, built-in goal. sensors and wide spread represent one of these enabling technologies. Much research has been 2.1. Indoors Location Based Tracking (LBT) carried out on how handheld augmented reality can be used to enhance user experience in museums, Despite the wide success of Global positioning exhibitions or in other indoor environments. Some system (GPS) with location based mobile research attempted to contextually overlay 3D applications in outdoor settings, GPS does not characters on the mobile screen to interact with users provide the required accuracy indoors. Alternately, and guide them in the environment [18]. Others used various approaches were used for indoor location games to get many users to interact and enjoy a tour based tracking, either through the use of Infra-Red inside a building [14]. However, existing attempts in (IR) networks [1], Wireless-LAN (Wi-Fi) networks indoor environments are merely prototypes that for triangulating the location [2] or active Radio cannot be easily adopted in real life contexts. Frequency Identification (RFID) tags [8]. The The aim of this work is to provide an existing solutions for indoors location based tracking augmented reality application on the iPhone to allow require expensive infrastructure without a guarantee exhibitions’ visitors to enjoy access to dynamic of an acceptable level of accuracy for an AR information about the displayed items and share their application [8]. own comments if they please. Enabling these forms of interactions in a reliable, yet seamless manner is 2.2. Marker-less Tracking envisaged to promote wide adoption of the technology in any indoor exhibition. Marker-less tracking, or feature tracking does not Tracking techniques are the biggest challenge to require special markers to be introduced in the the usability of an AR client on mobile devices. application setting. It is based purely on computer Thus, we start this paper with a discussion of vision algorithms extracting the specific required existing tracking techniques to give a basic features from the incoming camera feed, for example, faces, buildings, objects, etc. Mobile based 2.3.2. 2D Barcodes feature tracking is gaining more attention as the processing power of current smart phones increases 2D Barcodes are gaining more popularity as fiducial to allow it [12, 4]. markers. The ISO standard Data Matrix barcode (see Even though, the concept behind marker-less figure 1(b)) can store up to 2KB of information [16]. tracking could provide the ultimate augmented However, in environments where only little reality experience for users, both indoors and information needs to be encoded, simpler markers outdoors, there are some major challenges for this are preferred. For example frame, split, BCH (Bose, approach that hinder its adoption, especially with Ray-Chaudhuri & Hocquenghem) (see figure 1(d)) mobile based applications. The machine learning and Standard markers (see figure 1(c)). These techniques used for feature detection demand high markers can be used for an ID-aware environments processing powers and advanced memory where the ID number is encoded as bits in the marker requirements. Scalability is another challenge for this itself. There are several benefits to such approach. approach since complex algorithms need to be Firstly, detection of ID-markers is always faster than developed for learning different features. Finally, for template-markers since no image matching is marker-less tracking can be severely crippled in required [6]. Secondly, the user does not have to mono-vision applications that use a single camera, provide marker images, but can freely choose any due to the difficulty in depth perception [10]. marker from a fixed set of patterns. Finally, in contrast to template markers, the user is not required 2.3. Marker-based Tracking to train the toolkits with new patterns since any valid marker is implicitly known to the system [17]. Frame Markers, also known as Fiducials, are symbols with and Split markers offer an extra benefit of enabling specific known patterns that are designed to be easily human understandable information in addition to the recognized by machines [11, 6]. The maker-based encoded ID. However, they are only supported by a technique is the most commonly used indoor few toolkits of which none is available for licensing. tracking technology. This is because it relies on Section 2.4 provides more details about BCH and relatively simple software algorithms that do not Standard ID markers. require high processing powers nor expensive special built-in sensors. The following subsections provide an overview of some of the most common types of markers: template, 2D Barcodes and topological markers. (a) A Template (b) Data Matrix (c) A Standard (d) A BCH ID 2.3.1. Template Markers Marker. Marker ID Marker Marker Figure 1. Several Types of Markers used in marker based Template markers are one of the earliest fiducial tracking. markers developed. Template markers are basically a square with a black or white border with a 2.3.3. Topological markers contrasting background (white/black respectively) that can have anything inside of it. The whole square Topology based markers, such as D-Touch [6], are a with the pattern inside it are recognized as a marker, class of markers that are recognized based on (see figure 1(a)). Being a first however, template topological features of the markers rather than their markers suffer from some drawbacks. Firstly, when a geometry. Marker recognition is not based on shape, marker is detected, its pattern is extracted and cross- but on the relationship of dark and light regions. As a correlated with all known patterns. Consequently, as consequence, the visual design of the markers is less the patterns used increase and as the markers in the constrained and can be governed by aesthetic input image increase, the application becomes slower principles. That’s form and function, rather than just [6, 17]. Secondly, template markers must first be function. This is their distinctive feature compared to designed and then trained for the toolkit to use them. similar systems. The markers can be visually Finally, the complexity of the marker pattern affects designed to convey meaning to people [5]. the efficiency of the tracking, where patterns with Topological markers seem as good candidates for our large black and white regions (i.e. low frequency application context since they allows the usage of patterns) are the most effective [3]. Template markers with better aesthetic qualities. Their main markers were originally developed for the drawback however is that each marker must be ARToolKit [9] and currently supported by the independently and uniquely designed and validated. ARToolKitPlus [17] and Studierstube ES [15]. This requirement would incur additional effort, cost and time on initial deployment and on scalability, as in the case of template markers. 2.4. Toolkits 3. System Design Considerations An augmented reality toolkit is a software library Exhibitions are information rich environments that that can be used to calculate camera position and can vastly vary in their settings. We target indoor orientation relative to physical markers in real time. environments where exhibits can change frequently We are interested in open source toolkits that can and are not tied to a specific location. Thus, the demonstrate an acceptable performance on a mobile deployment of our system with minimal effort and device and that is either compatible with or can be cost is an essential requirement for our solution. ported to the iPhone platform. Existing literature Such requirement rules out the use of indoor location introduced several non-commercial marker based based tracking and marker less tracking techniques toolkits for augmented reality, for example, for our solution, leaving us with marker based ARTag[7], Studierstube ES [13] and ARToolKitPlus tracking as the best suit for our solution.