Speeded up detection of squared fiducial markers

Visual markers are graphic symbols designed to be easily recognised by machines. They are traditionally used to track goods, but there is increasing interest in their application to mobile HCI. By scanning a visual marker through a camera phone users can retrieve localised information and access mobile services. One missed opportunity in current visual marker systems is that the markers themselves cannot be visually designed, they are not expressive to humans, and thus fail to convey information before being scanned. This paper provides an overview of d-touch, an open source system that allows users to create their own markers, controlling their aesthetic qualities. The system runs in real-time on mobile phones and desktop computers. To increase computational efficiency d-touch imposes constraints on the design of the markers in terms of the relationship of dark and light regions in the symbols. We report a user study in which pairs of novice users generated between 3 and 27 valid and expressive markers within one hour of being introduced to the system, demonstrating its flexibility and ease of use.

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Designable visual markers

Designable Visual Markers

We report a topological approach to fiducial recognition for real-time applications. Independence from geometry makes the system tolerant to severe distortion, and allows encoding of extra information. The method is based on region adjacency trees. After describing the mathematical foundations, we present a set of simulations to evaluate the algorithm and optimise the fiducial design.

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A Region Adjacency Tree Approach to the Detection and Design of Fiducials.

This paper explores the use of data from the Kinect sensor for performing augmented reality, with emphasis on cultural heritage applications. It is shown that the combination of depth and image correspondences from the Kinect can yield a reliable estimate of the location and pose of the camera, though noise from the depth sensor introduces an unpleasant jittering of the rendered view. Kalman filtering of the camera position was found to yield a much more stable view. Results show that the system is accurate enough for in situ augmented reality applications. Skeleton tracking using Kinect data allows the appearance of participants to be augmented, and together these facilitate the development of cultural heritage applications.

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Augmented reality applications for cultural heritage using Kinect

Real-time positioning for augmented reality on a custom parallel machine

A system for vision-based ego location using ‘targets’ or ‘fiducials’ is described. The system is robust and operates on commodity hardware in real time. The accuracy of the system is assessed and found to be good enough to support some augmented reality applications. Two example applications are described: the control of an avatar in a shared virtual environment and a video ‘joystick’ for manipulating 3D models.

A Vision-Based Location System using Fiducials.

This paper describes a mobile augmented reality system intended for in situ reconstructions of archaeological sites. The evolution of the system from proof of concept to something approaching a satisfactory ergonomic design is described, as are the various approaches to achieving real-time rendering performance from the accompanying software. Finally, some comments are made concerning the accuracy of such systems.

Engineering an augmented reality tour guide

The Linux cluster considered in this paper, formed from shuttle box XPC nodes with 2 GHz Athlon processors connected by dual Gb Ethernet switches, is relatively easily constructed, but, while effective as a throughput engine, may result in disappointing results when running explicitly parallel software if weakly-performing communication mechanisms and process spawning are selected. This paper carefully compares the implementations of communication and spawning primitives in MPICH-2, openMosix, and Linux Remote Procedure Call, forking, and various lower-level communication mechanisms. The test selection compares the provision of both a message-passing library, and a single system image software package, with direct use of lower-level primitives. The information in the paper will be of interest to those considering the use of one of the well-known packages, or directly writing their own distributed applications, or constructing a distributed language by layering on top of an existing set of parallel primitives. The results expose a ranking in terms of process spawning and a similar ranking of communication software performance. They reveal poor performance in certain circumstances, well below the hardware specification, which it is as well that the developer is aware of. In general, the paper emphasizes the importance of efficient transport software to cluster machines.

Performance of parallel communication and spawning primitives on a Linux cluster

Parallel image processing has been a topic of interest for many years, but has not yet delivered a design methodology which can maintain portability across rapidly changing parallel implementation technologies. The two hurdles to be overcome are the difficulties of re-arranging application code into a parallel form and the lack of a general and universally supported parallel machine model. This paper addresses these problems using a functional language transformation, illustrated in the context of a particular application. We show that the overhead introduced by the transformation is relatively small, but the benefit derived is substantial, since the functional programming discipline enforces an implementation-independent definition of core parallel requirements, which can then be mapped onto a broad set of parallel architectures, ranging from shared and distributed memory conventional multiprocessors to direct hardware implementations constructed using silicon compilers and FPGA technology.

David J. Johnston

Papers

Real-time positioning for augmented reality on a custom parallel machine

A Vision-Based Location System using Fiducials.

Engineering an augmented reality tour guide

Performance of parallel communication and spawning primitives on a Linux cluster

A functional methodology for parallel image processing development