


Vol 42, No 6 (2016)
- Year: 2016
- Articles: 8
- URL: https://ogarev-online.ru/0361-7688/issue/view/10833
Article
Construction of a model of a continuous light source specified by a fixed set of rays
Abstract
A physically correct model of a light source specified by a finite set of rays obtained either by processing the measured characteristics of the light source on the Radiant Imaging goniometric system or as a result of the forward stochastic ray tracing in a scene modeling the radiation of a complex light source is constructed. An algorithm for constructing a continuous emitting surface of a light source and its goniometric diagram given a finite set of rays is developed. The model preserves the spectral composition of the source rays in the surface luminance distribution of the radiation light source. An example of the photorealistic rendering of a scene illuminated by a finite set of rays obtained by the computer processing photometric measurement data.



Algorithms for the construction and recognition of navigational route descriptions for cartographic computer systems
Abstract
In the modern world, the integration of computers with robotic devices has been steadily enhanced. This calls for the development of interfaces for the interaction of users with robotic systems. An important part of this task is the transfer of knowledge about the route, which can be passed from the user to a robotic system or from a robotic system to the user. This requires a special format for the route description that can be understandable for the user and can be recognized by the robot. In addition, it is required to personalize the transferred data for each specific user. Presently, there are many systems that partially execute these tasks—these are automobile navigators, applications for mobile and desktop computers, Web applications, etc. Such systems enable its users to find an optimal path and present their results (mainly on a display) as instructions on following the route. Typically, these instructions do not refer to landmarks that are familiar to the user. There is either impossible to input a route into such systems or this possibility is very limited. In this paper, we consider algorithms for the construction and recognition of textual descriptions of a route in the form that is convenient for the users taking into account their cognitive abilities and personal knowledge of surrounding objects.



A unified approach to adapt scientific visualization systems to third-party solvers
Abstract
This paper presents a new unified approach to adapt scientific visualization systems to third-party solvers implemented on different software and hardware platforms. This approach allows building multiplatform visualization systems, enables automatic conversion of input and output data from any solver into a rendering-compatible format, and provides real-time generation of high-quality images. The automated adaptation of visualization systems to third-party solvers is based on ontological engineering methods. Multiplatform portability is provided by the automatic generation of a graphical user interface (GUI) for each particular operating system and by preprocessing the data to be rendered by using heuristic-based tools, which ensures compatibility with different hardware and software platforms, including desktop computers and mobile devices. In addition, an original anti-aliasing algorithm is proposed to ensure high quality of resulting images. Based on the proposed approach, a multiplatform scientific visualization system called SciVi is developed, which is successfully used for solving various real-world scientific visualization problems from different application domains.



Full anatomical labeling of magnetic resonance images of human brain by registration with multiple atlases
Abstract
The problem of automatic segmentation of magnetic resonance (MR) images of human brain into anatomical structures is considered. Currently, the most popular segmentation algorithms are based on the registration (matching) of the input image with (to) an atlas—an image for which an expert labeling is known. Segmentation on the basis of registration with multiple atlases allows one to better take into account anatomical variability and thereby to compensate, to some extent, for the errors of matching to each individual atlas. In this work, a more efficient (in speed and memory) implementation is proposed of one of the best multiatlas label fusion algorithms in order to obtain a labeling of the input image. The algorithm is applied to the problem of segmentation of brain MR images into 43 anatomical regions with the use of the publicly available IBSR database, in contrast to the original work, where the authors provide test results for the problem of extraction of a single anatomical structure, the hippocampus.



Estimation of the people position in the world coordinate system for video surveillance
Abstract
A method is proposed for estimating the position of people in a scene when their head locations are known in the image plane. An extension of the approach is presented for processing several observations of the same person. It is shown that the algorithm proposed can be incorporated in the existing tracking methods involving a video from a static camera.



Algorithms for the analysis and visualization of high dynamic range images based on human perception
Abstract
High dynamic range images are used to store and transfer an extended range of intensities to render them on a display. To reproduce such images on displays with a lower range, tone mapping algorithms are used. The tone mapping algorithm described in this paper is a modification of the globally optimized linear windowed tone mapping algorithm. This modification is based on the human vision system model; it makes it possible to improve the results produced by the algorithm and replaces the nonintuitive parameters with a number of intuitively clear ones the variation of which in a high range does not visually distort the image. The high quality of the results produced by the algorithm is confirmed by the high TMQI index and the low value of the DRIM metric.



Methods of spatial indexing of dynamic scenes based on regular octrees
Abstract
The paper is devoted to study and development of spatial indexing methods as applied to three dimensional scenes arising in computer graphics, CAD/CAM systems, robotics, virtual and augmented reality applications, nD-modeling systems, and in project planning. Such scenes are compositions of a great number of extended geometrical objects exhibiting individual dynamic behaviors. The main focus is placed on algorithms for executing typical spatial queries with the use of regular dynamic octrees. In particular, algorithms for determining collisions, region search and nearest neighbor search are studied. For the model datasets introduced, average complexity estimates of index construction and execution of typical queries are derived based on probabilistic analysis. The estimates obtained significantly improve known pessimistic results and justify the suitability of regular octrees to spatial indexing of large-scale dynamic scenes. Results of computational experiments substantiate theoretical results and demonstrate possibilities of creating efficient computer graphics applications under the condition of permanently growing complexity of visual models.



Low overhead path regeneration
Abstract
Monte Carlo Path Tracing is a core light transport technique which is used for modern methods (like BDPT, MLT, VCM and others). One of the main challenge of efficient GPU Path Tracing implementation is inefficient workload caused by paths of different lengths; few threads process the long paths, while other threads are idle. A work distribution technique called “Path Regeneration” is commonly used to solve this problem. We introduce a novel GPU implementation of path regeneration technique called “in place block based path regeneration.” In comparison to previous approaches our algorithm possesses two main advantages: it has lower self-cost and it does not move any per-ray data along threads in memory, thus, our algorithm can be easily integrated to any advanced path tracing technique (like BDPT, MLT and other) or photon mapping. We tested our solution with path tracing using both CUDA and OpenCL.


