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101.
Photorealistic visualization of a huge number of individual filaments like in the case of hair, fur, or knitwear is a challenging task: Explicit rendering approaches for simulating radiance transfer at a filament get totally impracticable with respect to rendering performance and it is also not obvious how to derive efficient scattering functions for different levels of (geometric) abstraction or how to deal with very complex scattering mechanisms. We present a novel uniform formalism for light scattering from filaments in terms of radiance, which we call the bidirectional fiber scattering distribution function (BFSDF). We show that previous specialized approaches, which have been developed in the context of hair rendering, can be seen as instances of the BFSDF. Similar to the role of the BSSRDF for surface scattering functions, the BFSDF can be seen as a general approach for light scattering from filaments, which is suitable for deriving approximations in a canonic and systematic way. For the frequent cases of distant light sources and observers, we deduce an efficient far field approximation (bidirectional curve scattering distribution function, BCSDF). We show that on the basis of the BFSDF, parameters for common rendering techniques can be estimated in a non-ad-hoc, but physically-based way 相似文献
102.
Anna Korzynska Wojciech Strojny Andreas Hoppe David Wertheim Pawel Hoser 《Pattern Analysis & Applications》2007,10(4):301-319
This paper describes a segmentation method combining a texture based technique with a contour based method. The technique
is designed to enable the study of cell behaviour over time by segmenting brightfield microscope image sequences. The technique
was tested on artificial images, based on images of living cells and on real sequences acquired from microscope observations
of neutrophils and lymphocytes as well as on a sequence of MRI images. The results of the segmentation are compared with the
results of the watershed and snake segmentation methods. The results show that the method is both effective and practical.
相似文献
Anna KorzynskaEmail: |
103.
Priv. Doz. Dr. Horst Treiblmaier Univ. Ass. Dr. Andreas Strebinger 《WIRTSCHAFTSINFORMATIK》2006,48(2):87-95
We analyze the influence of B2C e-commerce on IT structure and brand architecture based on conceptual considerations, a case study and an empirical survey. We first discuss the changes in transaction costs that are induced by B2C e-commerce. The effects of B2C e-commerce on IT structure and brand architecture, which are anticipated from a transaction cost perspective, are illustrated using a case study from the tourism industry. We conducted a quantitative study among 101 chief information officers (CIOs) and chief marketing officers (CMOs) from the most important consumer brand companies in Austria. The results of a correspondence analysis show that a high importance of e-commerce triggers a typical bundle of changes in IT structure and brand architecture, which point toward a stronger integration within and between these two structural elements. We therefore conclude that B2C e-commerce calls for a better coordination of those measures that impact IT structure and brand architecture. 相似文献
104.
3D distance fields: a survey of techniques and applications 总被引:2,自引:0,他引:2
Jones MW Baerentzen JA Sramek M 《IEEE transactions on visualization and computer graphics》2006,12(4):581-599
A distance field is a representation where, at each point within the field, we know the distance from that point to the closest point on any object within the domain. In addition to distance, other properties may be derived from the distance field, such as the direction to the surface, and when the distance field is signed, we may also determine if the point is internal or external to objects within the domain. The distance field has been found to be a useful construction within the areas of computer vision, physics, and computer graphics. This paper serves as an exposition of methods for the production of distance fields, and a review of alternative representations and applications of distance fields. In the course of this paper, we present various methods from all three of the above areas, and we answer pertinent questions such as How accurate are these methods compared to each other? How simple are they to implement?, and What is the complexity and runtime of such methods? 相似文献
105.
Time-Constrained Keyframe Selection Technique 总被引:1,自引:0,他引:1
In accessing large collections of digitized videos, it is often difficult to find both the appropriate video file and the portion of the video that is of interest. This paper describes a novel technique for determining keyframes that are different from each other and provide a good representation of the whole video. We use keyframes to distinguish videos from each other, to summarize videos, and to provide access points into them. The technique can determine any number of keyframes by clustering the frames in a video and by selecting a representative frame from each cluster. Temporal constraints are used to filter out some clusters and to determine the representative frame for a cluster. Desirable visual features can be emphasized in the set of keyframes. An application for browsing a collection of videos makes use of the keyframes to support skimming and to provide visual summaries. 相似文献
106.
Humans manage to adapt learned movements very quickly to new situations by generalizing learned behaviors from similar situations. In contrast, robots currently often need to re-learn the complete movement. In this paper, we propose a method that learns to generalize parametrized motor plans by adapting a small set of global parameters, called meta-parameters. We employ reinforcement learning to learn the required meta-parameters to deal with the current situation, described by states. We introduce an appropriate reinforcement learning algorithm based on a kernelized version of the reward-weighted regression. To show its feasibility, we evaluate this algorithm on a toy example and compare it to several previous approaches. Subsequently, we apply the approach to three robot tasks, i.e., the generalization of throwing movements in darts, of hitting movements in table tennis, and of throwing balls where the tasks are learned on several different real physical robots, i.e., a Barrett WAM, a BioRob, the JST-ICORP/SARCOS CBi and a Kuka KR?6. 相似文献
107.
We give a #NC 1 upper bound for the problem of counting accepting paths in any fixed visibly pushdown automaton. Our algorithm involves a non-trivial adaptation of the arithmetic formula evaluation algorithm of Buss, Cook, Gupta and Ramachandran (SIAM J. Comput. 21:755?C780, 1992). We also show that the problem is #NC 1 hard. Our results show that the difference between #BWBP and #NC 1 is captured exactly by the addition of a visible stack to a nondeterministic finite-state automaton. 相似文献
108.
The Entity-Relationship (ER) model is a fundamental tool for database design, recently extended and employed in knowledge representation and reasoning due to its expressiveness and comprehensibility. We address the problem of answering conjunctive queries under constraints representing schemata expressed in an extended version of the Entity-Relationship model. This extended model, called ER+, comprises is-a constraints among entities and relationships, plus functional and mandatory participation constraints. In particular, it allows for arbitrary permutations of the roles in is-a among relationships. A key notion that ensures high tractability in ER+ schemata is separability, i.e., the absence of interaction between the functional participation constraints and the other constructs of ER+. We provide a precise syntactic characterization of separable ER+ schemata by means of a necessary and sufficient condition. We present a complete complexity analysis of the conjunctive query answering problem under separable ER+ schemata, and also under several sublanguages of ER+. We show that the addition of so-called negative constraints does not increase the complexity of query answering. With such constraints, our model properly generalizes the most widely adopted tractable ontology languages, including those in the DL-Lite family. 相似文献
109.
Andreas L?cken Tobias Hesselmann Martin Pielot Niels Henze Susanne Boll 《Multimedia Systems》2012,18(1):15-31
Music is a fundamental part of most cultures. Controlling music playback has commonly been used to demonstrate new interaction
techniques and algorithms. In particular, controlling music playback has been used to demonstrate and evaluate gesture recognition
algorithms. Previous work, however, used gestures that have been defined based on intuition, the developers’ preferences,
and the respective algorithm’s capabilities. In this paper we propose a refined process for deriving gestures from constant
user feedback. Using this process every result and design decision is validated in the subsequent step of the process. Therefore,
comprehensive feedback can be collected from each of the conducted user studies. Along the process we develop a set of free-hand
gestures for controlling music playback. The situational context is analysed to shape the usage scenario and derive an initial
set of necessary functions. In a successive user study the set of functions is validated and proposals for gestures are collected
from participants for each function. Two gesture sets containing static and dynamic gestures are derived and analysed in a
comparative evaluation. The comparative evaluation shows the suitability of the identified gestures and allows further refinement.
Our results indicate that the proposed process, that includes validation of each design decision, improves the final results.
By using the process to identify gestures for controlling music playback we not only show that the refined process can successfully
be applied, but we also provide a consistent gesture set that can serve as a realistic benchmark for gesture recognition algorithms. 相似文献
110.
Christian Bur Peter Reimann Mike Andersson Anita Lloyd Spetz Andreas Schütze 《Microsystem Technologies》2012,18(7-8):1015-1025
A silicon carbide based enhancement type metal insulator field effect transistor with porous gate metallization has been investigated as a total NO x sensor operated in a temperature cycling mode. This operating mode is quite new for gas sensors based on the field effect but promising results have been reported earlier. Based on static investigations we have developed a suitable T-cycle optimized for NO x detection and quantification in a mixture of typical exhaust gases (CO, C2H4, and NH3). Significant features describing the shape of the sensor response have been extracted and evaluated with multivariate statistics (e.g. linear discriminant analysis) allowing quantification of NO x . Additional cleaning-cycles every 30?min improve the stability of the sensor further. With this kind of advanced signal processing the influence of sensor drift and cross sensitivity to ambient gases can be reduced effectively. Measurements have proven that different concentrations of NO x can be detected even in a changing mixture of other typical exhaust gases under dry and humid conditions. In addition to that, unknown concentrations of NO x can be detected based on a small set of training data. It can be concluded that the performance of GasFETs for NO x determination can be enhanced considerably with temperature cycling and appropriate signal processing. 相似文献