Compression of point clouds has so far been confined to coding the positions of a discrete set of points in space and the attributes of those discrete points. We introduce an alternative approach based on volumetric f...
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Compression of point clouds has so far been confined to coding the positions of a discrete set of points in space and the attributes of those discrete points. We introduce an alternative approach based on volumetric functions that are functions defined not just on a finite set of points but throughout space. As in regression analysis, volumetric functions are continuous functions that are able to interpolate values on a finite set of points as linear combinations of continuous basis functions. Using a B-spline wavelet basis, we are able to code volumetric functions representing both geometry and attributes. Geometry compression is addressed in Part II of this paper, while attribute compression is addressed in Part I. Attributes are represented by a volumetric function whose coefficients can be regarded as a critically sampled orthonormal transform that generalizes the recent successful Region-Adaptive Hierarchical (or Haar) Transform to higher orders. Experimental results show that attribute compression using higher order volumetric functions is an improvement over the first-order functions used in the emerging MPEG point cloud compression standard.
Recent neuroscientific findings concerning the relationship between the perceptive, cognitive and linguistic aspects of colour suggest that colour concept retrieval would be enhanced by free colour naming or by the us...
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Recent neuroscientific findings concerning the relationship between the perceptive, cognitive and linguistic aspects of colour suggest that colour concept retrieval would be enhanced by free colour naming or by the use of natural associations between colour concepts and colour words. To test this hypothesis, we had subjects give their own free associations to a set of 35 colours presented on a display. The results suggest that subjects with normal colour vision are able to identify absolutely 30 colours or more without training if colours are well separated, basic colours are used and colour concepts and colour words are naturally associated.
color difference calculations are usually applied to match or tolerance of small differences between large (>2 degrees) visual fields. In contrast, we examine here the application of ultra-large color differences t...
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color difference calculations are usually applied to match or tolerance of small differences between large (>2 degrees) visual fields. In contrast, we examine here the application of ultra-large color differences to enhance conspicuousness and discriminability of small (1 degrees subtense or smaller) visual targets, e.g., in visual information displays. We show that CIEDE2000, and color difference metrics based on the OSA Uniform color Space and CIECAM02 are superior to CIELAB and CIELUV. Considering gray scale only, we show that Whittle's JND metric of achromatic contrast is as good as L* for this purpose, while also modeling contrast polarity and "crispening." Furthermore, using this JND metric, we replicate Highnote's finding that elongation of small targets affects their apparent contrast. We discuss the perceived fading of color differences when targets become smaller, and suggest practical methods to mitigate the adverse effect on color conspicuousness and discriminability. (C) 2009 Wiley Periodicals, Inc. Cot Res Appl, 35, 4-17, 2010;Published online 17 November 2009 in Wiley InterScience (***). DOI 10.1002/col.20557
Based on the measurements of 1063 flower reflection spectra, we show that flower colours fall into distinct dusters in the colour space of a bee. It is demonstrated that this clustering is caused by a limited variabil...
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Based on the measurements of 1063 flower reflection spectra, we show that flower colours fall into distinct dusters in the colour space of a bee. It is demonstrated that this clustering is caused by a limited variability in the floral spectral reflectance curves. There are as few as 10 distinct types of such curves, five of which constitute 85% of all measurements. UV reflections are less frequent and always lower in intensity than reflections in other parts of the spectrum. A further cluster of colour loci is formed in the centre of the colour space. It contains the colour loci of green leaves, several other background materials and only very few flowers. We propose a system to classify the reflection functions of flowers, and a set of colour names for bee colours.
Several variants of the subgraph isomorphism problem, e.g., finding, counting, and estimating frequencies of subgraphs in networks arise in a number of real world applications, such as web analysis, disease diffusion ...
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Several variants of the subgraph isomorphism problem, e.g., finding, counting, and estimating frequencies of subgraphs in networks arise in a number of real world applications, such as web analysis, disease diffusion prediction, and social network analysis. These problems are computationally challenging in having to scale to very large networks with millions of vertices. In this paper, we present SAHAD, a MapReduce algorithm for detecting and counting trees of bounded size using the elegant color coding technique developed by N. Alon et al. SAHAD is a randomized algorithm, and we show rigorous bounds on the approximation quality and the performance of it. SAHAD scales to very large networks comprising of 10(7) - 10(8) vertices and 10(8) - 10(9) edges and tree-like (acyclic) templates with up to 12 vertices. Further, we extend our results by implementing SAHAD in the Harp framework, which is more of a high performance computing environment. The new implementation gives 100x improvement in performance over the standard Hadoop implementation and achieves better performance than state-of-the-art MPI solutions on larger graphs.
The fruit fly Drosophila melanogaster can process chromatic information for true color vision and spectral preference. Spectral information is initially detected by a few distinct photoreceptor channels with different...
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The fruit fly Drosophila melanogaster can process chromatic information for true color vision and spectral preference. Spectral information is initially detected by a few distinct photoreceptor channels with different spectral sensitivities and is processed through the visual circuit. The neuroanatomical bases of the circuit are emerging. However, only little information is available in chromatic response properties of higher visual neurons from this important model organism. We used in vivo whole-cell patch-clamp recordings in response to monochromatic light stimuli ranging from 300 to 650 nm with 25-nm steps. We characterized the chromatic response of 33 higher visual neurons, including their general response type and their wavelength tuning. color-opponent-type responses that had been typically observed in primates and bees were not identified. Instead, the majority of neurons showed excitatory responses to broadband wavelengths. The UV (300-375 nm) and middle wavelength (425-575 nm) ranges could be separated at the population level owing to neurons that preferentially responded to a specific wavelength range. Our results provide a first mapping of chromatic information processing in higher visual neurons of D. melanogaster that is a suitable model for exploring how color-opponent neural mechanisms are implemented in the visual circuits.
Bipolar cells were studied in Golgi-Colonnier-stained whole mounts of macaque monkey retinae. A piece of retina, at 6-7 mm eccentricity, was particularly well stained for the analysis of the different bipolar cell typ...
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Bipolar cells were studied in Golgi-Colonnier-stained whole mounts of macaque monkey retinae. A piece of retina, at 6-7 mm eccentricity, was particularly well stained for the analysis of the different bipolar cell types. Many midget bipolar cells were encountered and the dichotomy into flat and invaginating midget bipolars was confirmed. Six types of diffuse cone bipolar cell are distinguished. They differ in their dendritic branching pattern, in the number of cones contacted-usually between five and ten-and in the shape and branching level of their axons. The size, shape and stratification of the axons were found to be the most reliable distinguishing features for classifying diffuse cone bipolar cells. The stratification of the axons in the inner plexiform layer (IPL), whether closer to the amacrine or ganglion cells, was used to name diffuse cone bipolar cells in the order DB1 to DB6. Blue cone and rod bipolar cells were confirmed as distinct types. Axon terminals of diffuse cone bipolars were found to tile their sublamina of the IPL in a territorial manner. From this the density of each type could be estimated, and it is shown that a single cone is likely to be in contact with as many as 15 individual diffuse bipolar cells, as well as two midget bipolars. The diffuse bipolar cells observed contact all the cone pedicles in their dendritic fields. It is, therefore, unlikely that they carry a chromatic signal into the inner retina. The presence of many midget bipolar cells, which make contact with one cone pedicle only, suggests that midget bipolars provide chromatic input to ganglion cells in peripheral retina as well as in the fovea. The data show that the P- and M-cell pathways of the primate visual system are, to a significant extent, already anatomically discrete at the photoreceptor synapse.
color display is useful in medical ultrasonography to increase sensitivity to contrast, to improve quantitative comparability between image regions, and to allow multiparameter display. In its first section this paper...
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color display is useful in medical ultrasonography to increase sensitivity to contrast, to improve quantitative comparability between image regions, and to allow multiparameter display. In its first section this paper expands upon these objectives, sets forth the concepts of color definition, and discusses the criteria that should be used to select a pseudocolor display scale. The second section surveys the published work applying color display in ultrasonography, and the final section presents some of our recent results on (1) producing continuous pseudocolor scales with a natural order and with the property that equal changes in driving signal produce equally perceptible changes along the pseudocolor scale; and (2) applying these scales to ultrasound images.
This paper reports on two experiments in which subjects' eye movement behaviour was monitored while they searched for target information in colour coded and monochrome horizontal situation indicator (HSI) displays...
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This paper reports on two experiments in which subjects' eye movement behaviour was monitored while they searched for target information in colour coded and monochrome horizontal situation indicator (HSI) displays. The first experiment required subjects to locate and report alphanumeric information associated with the active waypoint on the displayed flightpath. Initial fixations in the display were more accurately directed to the target information when it was redundantly colour coded compared with when it was coded by shape and relative positional codes. Fewer fixations and a shorter time were required to locate the colour coded target and verbally report the relevant information. The time advantage of colour coded displays compared with monochrome displays was greatest for visually cluttered displays. In the second study there was no advantage of a coloured display when the task was to count all the displayed waypoint symbols on the flight path. The lack of any benefit for colour coding was a result of waypoint symbols having strong positional predictability due to their relationship to the displayed flightpath in both the colour and monochrome displays. The implication from these results is that colour coded information confers an advantage over a spatial code for targets at unknown spatial location but less benefit when target location can be predicted by other visual cues.
We present CARTscans, a graphical tool that displays predicted values across. a four-dimensional subspace. We show how these plots are useful for understanding the structure and relationships between variables in a wi...
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We present CARTscans, a graphical tool that displays predicted values across. a four-dimensional subspace. We show how these plots are useful for understanding the structure and relationships between variables in a wide variety of models. including (but not limited to) regression trees, ensembles of trees, and linear regressions with varving degrees of interactions. In addition, the common visualization framework allows diverse complex models to be visually compared in a way that illuminates the similarities and differences in the underlying methods, facilitates the choice of a particular model structure, and provided a useful check for implausible predictions of future observations in regions With little or no data.
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