Papers by Konstantin Kolchin
A scheme for device-independent calculation of the color of light reflected by, or transmitted th... more A scheme for device-independent calculation of the color of light reflected by, or transmitted through, an object is presented. This scheme involves expressing object and light colors in display color space, so it is suitable for hardware implementation. Surface color is considered to be a linear operator acting on a 3-vector representing light, so the color of reflected (transmitted) light is the product of a matrix and a vector. Because contemporary hardware does not support matrix representation of color, we suggest a simplified version of the scheme, which uses only 3-vector representation of color.
Abstract Metallic and pearlescent paints contain flakes and exhibit strong texture (spatial fluct... more Abstract Metallic and pearlescent paints contain flakes and exhibit strong texture (spatial fluctuations of luminance) and spar- kles (rare, extremely bright tiny points). We present an al- gorithm for calculating these texture and sparkles during image rendering. Keywords: BRDF, paint texture.
A theoretical analysis is made of the feasibility of generating ultrashort optical pulses using a... more A theoretical analysis is made of the feasibility of generating ultrashort optical pulses using a traveling-wave electrooptic deflector in which a TEM radio wave, propagating in the same direction as a light wave, is used to modulate the refractive index of the deflector crystal. Various operating regimes of this deflector are analyzed and it is demonstrated that, in principle, pico- and femtosecond optical pulses can be obtained by this method.
Soviet Journal of Quantum Electronics, 1991
ABSTRACT A theoretical analysis is made of the feasibility of generating ultrashort optical pulse... more ABSTRACT A theoretical analysis is made of the feasibility of generating ultrashort optical pulses using a traveling-wave electrooptic deflector in which a TEM radio wave, propagating in the same direction as a light wave, is used to modulate the refractive index of the deflector crystal. Various operating regimes of this deflector are analyzed and it is demonstrated that, in principle, pico- and femtosecond optical pulses can be obtained by this method.
The paper introduces a new approximate method for rendering translucent materials. We represent t... more The paper introduces a new approximate method for rendering translucent materials. We represent the surface around a point to be rendered in Monge's form using principal curvatures. The subsurface reflectance equation in the dipole diffusion approximation is then integrated over the surface. The outgoing radiance at the point is expressed as a function of principal curvatures and light vector components along the principal directions. This function can be precomputed as a 2D lookup table, which can be stored as a texture image. The paper presents preliminary results of our work on implementation of the model described.
Physically based rendering of metallic and pearlescent appearance requires knowledge of the compo... more Physically based rendering of metallic and pearlescent appearance requires knowledge of the composition of paint or coating. However, sometimes composition is not available, while the Bi-directional Reflectance Distribution Function (BRDF) is measured from an actual sample. Such a situation invokes the inverse problem -to find a paint composition from a given BRDF. We solve this problem based on a two-layer paint model, where two basic kinds of pigments, flakes and microparticles, are separated in different layers. Because of this, appearance attributes -such as gloss, glitter, shade -are directly connected to the physical parameters of our model. Therefore, solution of the inverse problem can serve as a starting point for subsequent paint design that is done in appearancerelated rather than physical terms. Our solution involves two consecutive optimizations, which are calculated in real time on a contemporary PC.
Computer Graphics Forum, 2001
We describe a new approach to modelling pearlescent paints based on decomposing paint layers into... more We describe a new approach to modelling pearlescent paints based on decomposing paint layers into stacks of imaginary thin sublayers. The sublayers are chosen so thin that multiple scattering can be considered across different sublayers, while it can be neglected within each of the sublayers. Based on this assumption, an efficient recursive procedure of assembling the layers is developed, which enables to compute the paint BRDF at interactive speeds. Since the proposed paint model connects fundamental optical properties of multi-layer pearlescent and metallic paints with their microscopic structure, interactive prediction of the paint appearance based on its composition becomes possible.
The Visual Computer, 2004
We propose a new approach to interactive design of metallic and pearlescent coatings, such as aut... more We propose a new approach to interactive design of metallic and pearlescent coatings, such as automotive paints and plastic finishes of electronic appliances. This approach includes solving the inverse problem, that is, finding pigment composition of a paint from its bidirectional reflectance distribution function (BRDF) based on a simple paint model. The inverse problem is solved by two consecutive optimizations calculated in real-time on a contemporary PC. Such reverse engineering can serve as a starting point for subsequent design of new paints in terms of appearance attributes that are directly connected to the physical parameters of our model. This allows the user to have a paint composition in parallel with the appearance being designed.
We present several methods for simulation of Japanese lacquer ware, a prominent Far East Asian ha... more We present several methods for simulation of Japanese lacquer ware, a prominent Far East Asian handicraft art. We consider two most popular kinds of Japanese lacquerware made by the makie and nashiji techniques. For rendering makie, we propose a method for preparing RGBA textures from digital photos of art items. The alpha channels of these textures control the weight with which color channels are blended with the measured bidirectional reflectance distribution function (BRDF) of a metallic finish. Both ray tracing and hardware based rendering are demonstrated. In the latter case, we show how the calculation of a sphere map texture used for BRDF visualization can be accelerated using a special coordinate system for tabulated BRDF.
Most of the physically based techniques for rendering translucent objects use the diffusion theor... more Most of the physically based techniques for rendering translucent objects use the diffusion theory of light scattering in turbid media. The widely used dipole diffusion model [JMLH01] applies the diffusion-theory formula derived for the planar surface to objects of arbitrary shapes. The purpose of this communication paper is to present the very first results of our investigation of how surface curvature affects the diffuse reflectance from translucent materials.
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Papers by Konstantin Kolchin