Alexey G. Voloboy

Photorealistic volume scattering model in the bidirectional stochastic ray tracing problem

This paper is devoted to the development of physically correct rendering model of scenes containing volume scattering objects. The solution of the rendering equation is based on the Monte-Carlo bidirectional ray tracing. Two efficient approaches to the solution of the rendering equation for different parameters of the volume scattering medium (typically, concentration of scattering particles) are developed. Examples illustrate how the proposed models can be used for photorealistic visualization of scenes containing volume scattering objects and for the simulation of illuminators based on the volume scattering effect. Possible limitations of the application field of the proposed models are considered.

Integration of Realistic Computer Graphics into Computer-Aided Design and Product Lifecycle Management Systems

Various approaches to the integration of realistic image rendering and lighting simulation into computer-aided design systems are considered. An approach that ensures the effective integration of existing realistic image rendering systems into a CAD system is proposed. This approach makes it possible to utilize ready-to-use modules of a realistic image generation system, including the computation kernel and user interface modules. Synchronization of the executable modules of the basic and embedded systems is described. The proposed approaches and solutions were implemented in a project of integrating the lighting simulation and realistic image generation system Inspirer2 with the CAD CATIA.

Photorealistic Rendering of Images Formed by Augmented Reality Optical Systems

Stochastic ray tracing is used for rendering photorealistic images formed by augmented reality optical systems that combine the image generated by an optoelectronic device with the image of the environment. Methods for improving the efficiency of stochastic ray tracing that preserve the physical correctness of the simulation are proposed. Using a head-up display (HUD) as an example, it is shown that the forward stochastic ray tracing methods are sometimes more efficient than backward stochastic ray tracing methods for the visual simulation of augmented reality images. Approaches making it possible to combine the forward, backward, and bidirectional ray tracing in a unified simulation procedure are proposed. The results are illustrated by synthesized images produced by the optical system of head-up display.

Efficient Implementation of OpenGL SC for Avionics Embedded Systems

A software implementation of the graphics library OpenGL SC (Safety Critical) for the promising real-time onboard operating system JetOS for Russian aircraft is considered. The library development adheres to the international standards. The library must support multicore CPUs and be platform independent. The use of software implementation considerably reduces the cost of onboard software certification because it does not require the developers of graphics processors (GPUs) to be involved, which is sometimes impossible. The rendering speed achieved on specialized processors with low power consumption without the use of hardware accelerators satisfies the requirements of aviation applications.

Use of computer graphics methods for efficient stray light analysis in optical design

The problems of using stray light visualization for the effective analysis and design of complex optical systems are considered. Examples of real applications are given where the use of the light propagation criterion in conjunction with the visual representation of the ray path makes it possible to effectively analyze complex optical design problems. The suggested solution allows not only to visualize source of the stray light in the optical system but alto to render the image on the detector taking into account diffuse scattering on all illuminated surfaces.

Hybrid ray tracing method for photorealistic image synthesis in head-up displays

The paper describes the use of stochastic ray tracing methods for synthesizing of photorealistic images, formed by optical systems of augmented reality devices, that combines image synthesized by the optoelectronic device with the surrounding environment. As the result of the research, new methods are proposed that make it possible to increase the efficiency and preserve the physical correctness of stochastic ray tracing methods in the task of the photorealistic images synthesis formed by optical systems. The authors show that in such cases the methods of direct stochastic ray tracing are more effective for visual modeling of the augmented reality picture on an example of the head-up display (HUD) optical system. The proposed approaches allow to combine direct, inverse and bi-directional stochastic ray tracing methods in one calculation. The work is illustrated by examples of the synthesized images observed in HUD optical systems.

Realistic image synthesis in presence of birefrigent media by backward ray tracing technique

We describe an algorithm of tracing a backward (from camera) ray in a scene which contains birefrigent (uniaxial) media. The physics of scattering of an electromagnetic wave by a boundary between two media is well known and is a base for ray tracing algorithms; but processing of a backward ray differs from scattering of a “natural” forward ray. Say, when a backward ray refracts by a boundary, besides the energy transfer coefficient like for a forward ray one must account for the luminance change due to beam divergence. We calculate this factor and prove it must be evaluated only for the first and the last media along the ray path while the contributions from the intermediate media mutually cancel. In this paper we present a closed numerical method that allows to perform transformation of a backward ray on a boundary between two media either of which can be birefrigent. We hope it is more convenient and ready for usage in ray tracing engines that known publications. Calculation utilizes Helmholtz reciprocity to calculate directions of scattered rays and their polarization (i.e. Mueller matrices) which is advantageous over a straightforward “reverse” of forward ray transformation. The algorithm was integrated in the lighting simulation system Lumicept and allowed for an efficient calculation of images of scenes with crystal elements.

Simulation of the BSDF measurement capabilities for various materials with GCMS-4 gonio-spectrophotometer

Physically accurate lighting simulation requires precise account of the optical properties (BSDF) which are usually measured using gonio-spectrophotometer. In this paper, the authors analyzed the accuracy of BSDF shape measured for later use of measurements in special software for photorealistic visualization and virtual prototyping. Visual and numerical analysis were done. In the first case we look at the sample image rendered under specified lighting conditions, replacing its properties on measurement results and visually estimate the similarity (or difference). In the second case we compare the results of simulation of spatial or angular radiance distribution with results of corresponding radiometric measurements.

Improved model of IBL sunlight simulation

This paper considers the use of high dynamic range images as a source of natural daylight illumination in virtual scenes containing objects with complex optical properties (such as automotive multilayer paints). Physically justified algorithms for calculating the luminance of an object point and recognition of the sun to replace it by separate light source are outlined. An analysis of the correctness of the available high dynamic range images is performed, and their drawbacks are discussed. Two algorithms that allow to compensate the drawbacks of the representation of the visible sun in the high dynamic range images and thus perform a more accurate illumination simulation are proposed and elaborated. The correction of sun representation is based on the sky models adopted by the International Commission on Illumination (CIE). The modified illumination simulation algorithms make it possible to produce more accurate images. The algorithms are semi- automatic and robust with respect to errors in high dynamic range images. These algorithms are used in our computer graphics system for generating realistic images.