Improved method of the plane-sweep strategy in the task of building reconstruction from aerophotographs

Abstract: The tasks of detection and three-dimensional reconstruction of buildings are to be often solved as part of the terrain digitizing problem. Most of the algorithms used to solve this problem are too general and, as a result, are ineffective either in accuracy or in terms of operation time. In this paper we propose to use a modification of the plane-sweep strategy method. As a result of the proposed improvement, the reconstruction process is accelerated several times, while providing comparable quality.Note: Research direction:Programming, parallel computing, multimedi

Method of denoising for the image generated by Monte Carlo ray tracing preserving small details

Abstract: Monte-Carlo methods of ray tracing allow generating physically correct images of virtual scenes, reproducing a large number of optical effects. However, the resulting image contains noise inherent in stochastic algorithms. An original method of denoising in these images is proposed. Small-scale details of the image are not distorted because they are taken from an auxiliary, reference image constructed by a deterministic ray tracing. The reference image allows you to extract the secondary lighting component which is usually a smooth function and allows for efficient filtering. After multiplying its result by an auxiliary deterministic image, a sharp picture is obtained with preservation of small details and with greatly reduced noise.Note: Research direction:Mathematical modelling in actual problems of science and technic

Modification of the stochastic ray tracing to reduce a noise on diffuse surfaces

Abstract: Bidirectional Monte-Carlo methods of ray tracing allow you to effectively generate physically correct images of virtual scenes, reproducing a large number of optical effects. However, the resulting image contains noise inherent in stochastic algorithms. An original modification of the pixel brightness calculation process is proposed. It makes possible to significantly reduce noise on diffuse surfaces. The proposed method does not distort the texture and small-scale image details, because in fact the built-in tracing filtering applies not to the final image, but to effective illumination. The method works well for diffuse lighting but it is not beneficial for brightness created by direct or caustic lighting.Note: Research direction:Mathematical modelling in actual problems of science and technic

Filtering of the results of Monte Carlo ray tracing using multiple images

Abstract: This paper presents a method of filtering using several input images obtained by Monte Carlo ray tracing with small changes in the position of the virtual camera inside the scene. The limiting case with the absence of a camera shift, which actually degenerates into a distribution of independent samples to several Monte Carlo images, is considered separately. This approach does not impose any restrictions on the method of generating Monte Carlo samples and allows to take advantage of methods such as ray tracing on GPU and quasi-Monte Carlo. Unlike existing analogues, the proposed method takes into account the spread of Monte Carlo samples’ values for each virtual sub-pixel, which provides an opportunity for handling outliers and smoothing of aliasing effects while preserving details in the image.Note: Research direction:Mathematical modelling in actual problems of science and technic

Treating diffuse elements as quasi-specular to reduce noise in bi-directional ray tracing

Abstract: In simulation of the light propagation the brightness of each ray is calculated based on the optical properties of the virtual scene objects which it interacts with. According to the optical properties these objects can be roughly subdivided into diffuse and specular. The Monte-Carlo based ray tracing methods which are commonly used in simulation calculate the brightness only for diffuse surfaces. When a ray meets a specular surface it is reflected (or refracted) until it reaches a diffuse surface where the brightness is calculated. In the proposed approach diffuse elements are further divided into “truly diffuse” and “quasi-mirror”. The most natural criterion for the latter is scattering in a narrow cone around a purely specular direction. A scene element can also be a superposition of both types when its scattering function is treated as the sum of a truly diffuse and quasi-mirror parts. The work shows how various components of illumination interact with quasi-mirror objects and describes how this is implemented in the bi-directional Monte Carlo ray tracing. The proposed approach allows to significantly reduce the stochastic noise for a number of scenes including those for which it is not possible to achieve good results with any settings of the standard method. This method is also applicable to the simulation of volume scattering treating the phase function of the medium as quasi-mirror. In this case the selection of quasi-mirror objects is by no means based on the character of the scattering distribution function. For volume scattering the medium is treated as quasi-mirror while the surfaces, even if their scattering distribution functions are narrower, remain «truly diffuse'. The article shows the advantage of this approach.Note: Research direction:Mathematical modelling in actual problems of science and technic

Automatic testing of interactive lighting simulation software package

Abstract: The article is devoted to automatic regression testing technology used in development and maintenance within the life cycle of modern computer graphics and optical simulation software systems. The main types of errors and ways to implement tests using the command line, the Python script language, and the AutoIt package, which allow you to create tests for an interactive graphical user interface, are considered. In practice the described technology allows to reduce the time for testing the released version of a software product from several weeks to couple of hours.Note: Research direction:Mathematical modelling in actual problems of science and technic