1,292 research outputs found
Fidelity metrics for virtual environment simulations based on spatial memory awareness states
This paper describes a methodology based on human judgments of memory awareness
states for assessing the simulation fidelity of a virtual environment (VE) in relation
to its real scene counterpart. To demonstrate the distinction between task
performance-based approaches and additional human evaluation of cognitive awareness
states, a photorealistic VE was created. Resulting scenes displayed on a headmounted
display (HMD) with or without head tracking and desktop monitor were
then compared to the real-world task situation they represented, investigating spatial
memory after exposure. Participants described how they completed their spatial
recollections by selecting one of four choices of awareness states after retrieval in
an initial test and a retention test a week after exposure to the environment. These
reflected the level of visual mental imagery involved during retrieval, the familiarity
of the recollection and also included guesses, even if informed. Experimental results
revealed variations in the distribution of participants’ awareness states across conditions
while, in certain cases, task performance failed to reveal any. Experimental
conditions that incorporated head tracking were not associated with visually induced
recollections. Generally, simulation of task performance does not necessarily
lead to simulation of the awareness states involved when completing a memory
task. The general premise of this research focuses on how tasks are achieved,
rather than only on what is achieved. The extent to which judgments of human
memory recall, memory awareness states, and presence in the physical and VE are
similar provides a fidelity metric of the simulation in question
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Reconstructing Surfaces Using Anisotropic Basis Functions
Point sets obtained from computer vision techniques are often noisy and non-uniform. We present a new method of surface reconstruction that can handle such data sets using anisotropic basis functions. Our reconstruction algorithm draws upon the work in variational implicit surfaces for constructing smooth and seamless 3D surfaces. Implicit functions are often formulated as a sum of weighted basis functions that are radially symmetric. Using radially symmetric basis functions inherently assumes, however that the surface to be reconstructed is, everywhere, locally symmetric. Such an assumption is true only at planar regions, and hence, reconstruction using isotropic basis is insufficient to recover objects that exhibit sharp features. We preserve sharp features using anisotropic basis that allow the surface to vary locally. The reconstructed surface is sharper along edges and at corner points. We determine the direction of anisotropy at a point by performing principal component analysis of the data points in a small neighborhood. The resulting field of principle directions across the surface is smoothed through tensor filtering. We have applied the anisotropic basis functions to reconstruct surfaces from noisy synthetic 3D data and from real range data obtained from space carving
Joint Fractional Time Allocation and Beamforming for Downlink Multiuser MISO Systems
It is well-known that the traditional transmit beamforming at a base station
(BS) to manage interference in serving multiple users is effective only when
the number of users is less than the number of transmit antennas at the BS.
Non-orthogonal multiple access (NOMA) can improve the throughput of users with
poorer channel conditions by compromising their own privacy because other users
with better channel conditions can decode the information of users in poorer
channel state. NOMA still prefers that the number of users is less than the
number of antennas at the BS transmitter. This paper resolves such issues by
allocating separate fractional time slots for serving the users with similar
channel conditions. This enables the BS to serve more users within the time
unit while the privacy of each user is preserved. The fractional times and
beamforming vectors are jointly optimized to maximize the system's throughput.
An efficient path-following algorithm, which invokes a simple convex quadratic
program at each iteration, is proposed for the solution of this challenging
optimization problem. Numerical results confirm its versatility.Comment: IEEE Communications Letters (To Appear
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Reconstructing Surfaces by Volumetric Regularization Using Radial Basis Functions
We present a new method of surface reconstruction that generates smooth and seamless models from sparse, noisy, nonuniform, and low resolution range data. Data acquisition techniques from computer vision, such as stereo range images and space carving, produce 3D point sets that are imprecise and nonuniform when compared to laser or optical range scanners. Traditional reconstruction algorithms designed for dense and precise data do not produce smooth reconstructions when applied to vision-based data sets. Our method constructs a 3D implicit surface, formulated as a sum of weighted radial basis functions. We achieve three primary advantages over existing algorithms: (1) the implicit functions we construct estimate the surface well in regions where there is little data, (2) the reconstructed surface is insensitive to noise in data acquisition because we can allow the surface to approximate, rather than exactly interpolate, the data, and (3) the reconstructed surface is locally detailed, yet globally smooth, because we use radial basis functions that achieve multiple orders of smoothness
Automatically learning structural units in educational videos with the hierarchical hidden Markov models
In this paper we present a coherent approach using the hierarchical HMM with shared structures to extract the structural units that form the building blocks of an education/training video. Rather than using hand-crafted approaches to define the structural units, we use the data from nine training videos to learn the parameters of the HHMM, and thus naturally extract the hierarchy. We then study this hierarchy and examine the nature of the structure at different levels of abstraction. Since the observable is continuous, we also show how to extend the parameter learning in the HHMM to deal with continuous observations
The sweet smell of success: Enhancing multimedia applications with olfaction
This is the Post-Print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 ACMOlfaction, or smell, is one of the last challenges which multimedia applications have to conquer. As far as computerized smell is concerned, there are several difficulties to overcome, particularly those associated with the ambient nature of smell. In this article, we present results from an empirical study exploring users' perception of olfaction-enhanced multimedia displays. Findings show that olfaction significantly adds to the user multimedia experience. Moreover, use of olfaction leads to an increased sense of reality and relevance. Our results also show that users are tolerant of the interference and distortion effects caused by olfactory effect in multimedia
AdaBoost.MRF: boosted Markov random forests and application to multilevel activity recognition
Activity recognition is an important issue in building intelligent monitoring systems. We address the recognition of multilevel activities in this paper via a conditional Markov random field (MRF), known as the dynamic conditional random field (DCRF). Parameter estimation in general MRFs using maximum likelihood is known to be computationally challenging (except for extreme cases), and thus we propose an efficient boosting-based algorithm AdaBoost.MRF for this task. Distinct from most existing work, our algorithm can handle hidden variables (missing labels) and is particularly attractive for smarthouse domains where reliable labels are often sparsely observed. Furthermore, our method works exclusively on trees and thus is guaranteed to converge. We apply the AdaBoost.MRF algorithm to a home video surveillance application and demonstrate its efficacy
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