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Now showing 1 - 9 of 9
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    Feature Identification and Extraction in Function Fields
    (The Eurographics Association, 2007) Anderson, John C.; Gosink, Luke J.; Duchaineau, Mark A.; Joy, Kenneth I.; K. Museth and T. Moeller and A. Ynnerman
    We present interactive techniques for identifying and extracting features in function fields. Function fields map points in n-dimensional Euclidean space to 1-dimensional scalar functions. Visual feature identification is ac- complished by interactively rendering scalar distance fields, constructed by applying a function-space distance metric over the function field. Combining visual exploration with feature extraction queries, formulated as a set of function-space constraints, facilitates quantitative analysis and annotation. Numerous application domains give rise to function fields. We present results for two-dimensional hyperspectral images, and a simulated time-varying, three-dimensional air quality dataset.
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    Symmetry Descriptors and 3D Shape Matching
    (The Eurographics Association, 2004) Kazhdan, Michael; Funkhouser, Thomas; Rusinkiewicz, Szymon; Roberto Scopigno and Denis Zorin
    In this paper, we present the Symmetry Descriptors of a 3D model. This is a collection of spherical functions that describes the measure of a model's rotational and reflective symmetry with respect to every axis passing through the center of mass. We show that Symmetry Descriptors can be computed efficiently using fast signal processing techniques, and demonstrate the empirical value of Symmetry Descriptors by showing that they improve matching performance in a variety of shape retrieval experiments.
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    Rotation Invariant Spherical Harmonic Representation of 3D Shape Descriptors
    (The Eurographics Association, 2003) Kazhdan, Michael; Funkhouser, Thomas; Rusinkiewicz, Szymon; Leif Kobbelt and Peter Schroeder and Hugues Hoppe
    One of the challenges in 3D shape matching arises from the fact that in many applications, models should be considered to be the same if they differ by a rotation. Consequently, when comparing two models, a similarity metric implicitly provides the measure of similarity at the optimal alignment. Explicitly solving for the optimal alignment is usually impractical. So, two general methods have been proposed for addressing this issue: (1) Every model is represented using rotation invariant descriptors. (2) Every model is described by a rotation dependent descriptor that is aligned into a canonical coordinate system defined by the model. In this paper, we describe the limitations of canonical alignment and discuss an alternate method, based on spherical harmonics, for obtaining rotation invariant representations. We describe the properties of this tool and show how it can be applied to a number of existing, orientation dependent descriptors to improve their matching performance. The advantages of this tool are two-fold: First, it improves the matching performance of many descriptors. Second, it reduces the dimensionality of the descriptor, providing a more compact representation, which in turn makes comparing two models more efficient.
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    Illustrative Scientific Visualization Framework
    (The Eurographics Association, 2005) Sousa, Mario Costa; Gooch, Amy Ashurst; Gooch, Bruce; Laszlo Neumann and Mateu Sbert and Bruce Gooch and Werner Purgathofer
    Current scientific visualization techniques create complex images that may be difficult to interpret and do not have the expressiveness of illustrations. Incorporating traditional scientific illustration techniques into a visualization system enables artists and non-artists to harnesses the power of traditional illustration techniques when visually representing scientific data. In this paper we present an illustrative scientific visualization framework incorporating general illustration principles, as well as techniques and aesthetics of various styles. Such a framework provides a basic foundation for categorizing and communicating research and may stimulate future illustrative visualization systems.
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    Marker-less Real-time Camera Registration for Mixed Reality
    (The Eurographics Association, 2007) Liverani, Alfredo; Grandi, Stefania; Raffaele De Amicis and Giuseppe Conti
    A real-time and robust algorithm for 3D camera registration in a Mixed Reality (MR) environment is described in this paper. The most used technique for camera pose (position and orientation with respect to a fixed or moving object) is based on fiducial marker tracking. This method guarantees good results in real-time with a single camera, but needs several high contrast printed markers on external world in order to make possible the calculation of camera parameters and positioning. Thus real 3D geometric data are grabbed only through already known markers. The aim of this research is a real-time monocular camera tracking and registration through automatic image features extraction from video streaming. The first implementation of the method, several examples and confrontation with non interactive algorithm for SFM (Structure From Motion) have demonstrated that this meets the real-time response and sufficient precision needed by a Mixed Reality environment.
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    Reducing Fragmentation in Telecollaboration by Using IPT Interfaces
    (The Eurographics Association, 2005) Roberts, D.; Al-Liabi, M.; Wolff, R.; Otto, O.; Al-Khalifah, A.; Erik Kjems and Roland Blach
    Telecommunication systems, such as AccessGrid, allow collaboration across a distributed team. However, these systems typically introduce fragmentation into the view of the shared environment. Many have found that IPT systems offer several important advantages above other display technologies in supporting distance working. This study focuses on fragmentation, which has previously been shown to induce problems in efficient object referencing within a shared virtual environment accessed through desktop displays. We have attempted to repeat the experiment while varying the display type. The results reinforce previous studies by showing a significant improvement in task performance when the entire team uses IPT displays. We further show that the improvement is unlikely to come in this case from more natural interaction or navigation and thus postulate that it arises from more efficient mutual orientation towards objects of interest, arising from a reduction in fragmentation.
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    A Quantitative Assessment of the Impact on Spatial Understanding of Exploring a Complex Immersive Virtual Environment using Augmented Real Walking versus Flying
    (The Eurographics Association, 2007) Interrante, Victoria; O'Rourke, Eleanor; Gray, Leanne; Anderson, Lee; Ries, Brian; Bernd Froehlich and Roland Blach and Robert van Liere
    When an immersive virtual environment spans an area that is larger than the available physical space for real walking, one may use an augmented walking method such as Seven League Boots to enable participants to explore the space while gaining proprioceptive feedback that is similar to what they would experience with normal walking. In this paper, we present the results of a preliminary experiment in which we seek to quantitatively assess the extent to which participants are able to make more accurate spatial judgments about the locations of previously-seen targets in a complicated virtual city environment, experienced using a head-mounted display, after traveling to them using augmented real walking ( boots ) versus virtual walking enabled by a button press on a hand-held wand. In a series of trials, we ask participants to follow paths of increasing complexity from a home base to different hidden targets in the environment and back. At each endpoint, with the path markings turned off, we ask participants to point, through the intervening alleyway walls, to the location they believe they started from. Participants are able to make real turns with their bodies in both locomotion conditions, however they are able to make real forward movement only under the augmented walking condition. Each participant completes eight trials under each locomotion condition, with the target locations and the order of experiencing each method counterbalanced between participants. In data collected from six participants so far, we are finding that the median angle error is significantly greater, overall, in the wand locomotion condition than in the boots locomotion condition, and that the errors tend to increase, overall, as the path complexity increases (from two segments to four segments) in the wand locomotion condition but not in the boots locomotion condition.
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    Visualization Notations, Models and Taxonomies
    (The Eurographics Association, 2007) Brodlie, Ken; Noor, Nurul Mohd; Ik Soo Lim and David Duce
    Visualization taxonomies are an important means of imposing some structure on a rather diverse field. We review some earlier work in this area, particularly work based on the use of a notation to label classes of visualization techniques that are appropriate to particular entities. We propose a new notation introducing it in the context of a new visualization reference model, one we hope will lead eventually to a means of describing visualizations in a clear and unambiguous way.
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    Methods for Spatial Data Quality of 3D City Models
    (The Eurographics Association, 2007) Krämer, Michel; Haist, Jörg; Reitz, Thorsten; Raffaele De Amicis and Giuseppe Conti
    3D city models are nowadays used in very different applications. Due to this, the commercial exchange and, thus, the demand for high quality data becomes more and more important. We describe a quality model that defines common parameters used for spatial quality measurement, especially when dealing with 3D city models. Therefore, we explore different representations of city models: the reality, the user's idea and the digital data set. A welldefined mathematical formalism which addresses the different quality parameters is presented. This formalism also helps to create algorithms for measurement and improvement of spatial data quality. The aim is to be able to define uniformed criteria which can be easily transformed into software. The implemented prototype serves as base for the evaluation in which we provide examples based on actual data sets using typical quality requirements.