Kei Iwasaki

Saitama University · Department of Information and Computer Sciences

Artificial light sources make our daily life convenient, but cause a severe problem called light pollution. We propose a novel system for efficient visualization of light pollution in the night sky. Numerous methods have been proposed for rendering the sky, but most of these focus on rendering of the daytime or the sunset sky where the sun is the o...

In this paper, we present a geometric approach to render shadows for physically based materials under polygonal light sources. Direct illumination calculation from a polygonal light source involves the triple product integral of the lighting, the bidirectional reflectance distribution function (BRDF), and the visibility function over the polygonal...

The reflection of a bright light source on a dynamic surface such as water with waves can be difficult to render well in real time due to reflection aliasing and flickering. In this paper, we propose a solution to this problem by approximating the reflection direction distribution for the water surface as an elliptical Gaussian distribution. Then w...

Rendering a translucent material involves integrating the product of the transmittance-weighted irradiance and the BSSRDF over the surface of it. In previous methods, this spatial integral was computed by creating a dense distribution of discrete points over the surface or by importance-sampling based on the BSSRDF. Both of these approaches necessi...

Recent advances in bidirectional path tracing (BPT) reveal that the use of multiple light sub‐paths and the resampling of a small number of these can improve the efficiency of BPT. By increasing the number of pre‐sampled light sub‐paths, the possibility of generating light paths that provide large contributions can be better explored and this can a...

Bidirectional path tracing (BPT) with multiple importance sampling (MIS) is a popular technique for rendering realistic images. Recently, it has been shown that BPT can be improved by preparing multiple light sub-paths and by resampling a small number of light sub-paths from them to generate full paths with large contribution. Traditionally, for MI...

In this paper, we present a method to render shadows for physically-based materials under polygonal light sources. Direct illumination calculation from a polygonal light source involves the triple product integral of the lighting, the bidirectional reflectance distribution function (BRDF), and the visibility function over the polygonal domain, whic...

The ocean surface is highly dynamic. It moves rapidly and thus its shading changes rapidly as well. Usually, this doesn't pose any problems if the shading is smooth. However, for a surface that has a strong highlight or bright reflection moving rapidly, it causes an inaccurate and unnatural flickering. In the traditional rendering algorithms, each...

In many-light rendering, a variety of visual and illumination effects, including anti-aliasing, depth of field, volumetric scattering, and subsurface scattering, are combined to create a number of virtual point lights (VPLs). This is done in order to simplify computation of the resulting illumination. Naive approaches that sum the direct illuminati...

This paper proposes an inverse approach for modeling the appearance of interwoven cloth. Creating the desired appearance in cloth is difficult because many factors, such as the type of thread and the weaving pattern, have to be considered. Design tools that enable the desired visual appearance of the cloth to be replicated are therefore beneficial...

Many-light rendering unifies the computation of various visual and illumination effects, which include anti-aliasing, depth of field, volumetric scattering, and subsurface scattering, into a simple direct illumination computation from many virtual point lights (VPLs). As a naive approach that sums the direct illumination from a large number of VPLs...

A great deal of attention has been devoted to the fabrication of reflectors that can display different color images when viewed from different directions not only in industry but also for the arts. Although such reflectors have previously been successfully fabricated, the number of images displayed has been limited to two or they suffer from ghosti...

Solving the pressure Poisson equation dominates a large portion of computational time for incompressible fluid flow simulations. To solve the pressure Poisson equation efficiently, geometric multigrid methods are used directly or used as the preconditioner for the conjugate gradient (CG) method. Conventionally, the V‐cycle multigrid method is widel...

In this paper, we propose a modeling method of clouds from a single photograph. To synthesize realistic images of outdoor scenes, modeling of 3D clouds is necessary. However, synthesizing realistic clouds is still a difficult task. To address this problem, we propose an example-based volume texture synthesis to model nonhomogeneous density volumes....

We present a system that automatically suggests the furniture layout when one moves into a new house, taking into account the furniture layout in the previous house. In our method, the input to our system comprises the floor plans of the previous and new houses, and the furniture layout in the previous house. The furniture layout for the whole hous...

Clouds play an important role when synthesizing realistic images of outdoor scenes. The realistic display of clouds is therefore one of the important research topics in computer graphics. In order to display realistic clouds, we need methods for modeling, rendering, and animating clouds realistically. It is also important to control the shapes and...

The popularity of many-light rendering, which converts complex global illumination computations into a simple sum of the illumination from virtual point lights (VPLs), for predictive rendering has increased in recent years. A huge number of VPLs are usually required for predictive rendering at the cost of extensive computational time. While previou...

Realistic image synthesis is an important research goal in computer graphics. One important factor to achieve this goal is a bidirectional reflectance distribution function (BRDF) that mainly governs an appearance of an object. Many BRDF models have therefore been developed. A physically-based BRDF based on microfacet theory [Cook and Torrance 1982...

Physically based fluid simulations usually require expensive computation cost for creating realistic animations. We present a technique that allows the user to create various fluid animations from an input fluid animation sequence, without the need for repeatedly performing simulations. Our system allows the user to deform the flow field in order t...

Importance sampling of virtual point lights (VPLs) is an efficient method for computing global illumination. The key to importance sampling is to construct the probability function, which is used to sample the VPLs, such that it is proportional to the distribution of contributions from all the VPLs. Importance caching records the contributions of a...

Image-based lighting is widely used to represent real-world, complex lighting in recent years. Image-based lighting captures surrounding environment illumination as an environment map, and uses it for the illumination. Although realistic images can be rendered by using image-based lighting, the computational cost using image-based lighting can be p...

In this paper, we present an importance sampling method for the BRDF of cloth which consists of interwoven threads under environment light. As the scattering model for cloth, our method employs a microcylinder model proposed by Sadeghi et al [1]. In the microcylinder model, BRDF is represented by using Gaussian functions. Our method represents the...

Recently, visual simulation of fluids has become an important element in many applications, such as movies and computer games. These fluid animations are usually created by physically-based fluid simulation. However, the simulation often requires very expensive computational cost for creating realistic fluid animations. Therefore, when the user tri...

Image-based rendering methods have been widely used to render realistic images of scenes illuminated by real-world, complex lighting. Recent advances on image-based rendering methods have revealed that spherical Gaussian functions have several nice properties for rendering and are suited to represent all-frequency signals compactly and accurately s...

The visual simulation of fluids has become an important element in many applications, such as movies and computer games. In these applications, large-scale fluid scenes, such as fire in a village, are often simulated by repeatedly rendering multiple small-scale fluid flows. In these cases, animators are requested to generate many variations of a sm...

This paper proposes an interactive rendering method of cloth fabrics under environment lighting. The outgoing radiance from cloth fabrics in the microcylinder model is calculated by integrating the product of the distant environment lighting, the visibility function, the weighting function that includes shadowing/masking effects of threads, and the...

We present a technique for computing the shape of a transparent object that can generate user-defined caustic patterns. The surface of the object generated using our method is smooth. Thanks to this property, the resulting caustic pattern is smooth, natural, and highly detailed compared to the results obtained using previous methods. Our method con...

The visual simulation of fluids has become an important element in many applications, such as movies and computer games. In these applications, large-scale fluid scenes, such as fire in a village, are often simulated by repeatedly rendering multiple small-scale fluid flows. In these cases, animators are requested to generate many variations of a sm...

Glazed frost is a crystal clear ice and formed from supercooled raindrops that freeze when they hit object surfaces such as the ground and branches of trees. Simulation methods for formation of ice crystal, such as frost, on the surface of objects have been proposed by Kim et al. [Kim et al. 2004]. However, a supercooling state has to be considered...

Developing a robust method for computing global illumination is a challenging problem. A Markov chain Monte Carlo (MCMC) method, like [Jakob and Marschner 2012], samples the light path space with a probability proportional to the per-path contribution, by successively mutating path samples (e.g., perturbing a reflection direction). In practice, a p...

Divide-and-conquer ray tracing (DACRT) methods solve intersection problems between large numbers of rays and primitives by recursively subdividing the problem size until it can be easily solved. Previous DACRT methods subdivide the intersection problem based on the distribution of primitives only, and do not exploit the distribution of rays, which...

Fast computation of multiple reflections and scattering among complex objects is very important in photorealistic rendering. This paper applies the plane-parallel scattering theory to the rendering of densely distributed objects such as trees. We propose a simplified plane-parallel scattering model that has very simple analytic solutions, allowing...

In this paper, we propose a model to simulate magnetic fluids. Magnetic fluids behave as both fluids and as magnetic bodies, and these characteristics allow them to generate 'spike-like' shapes along a magnetic field. However, the spike shapes could not be reproduced by using the simulation method in the field of magnetic fluids. The spikes are dif...

Ice often contains small air bubbles that are dissolved air exhausted from water-ice interface. Depicting these air bubbles with various sizes enhances the realism of ice. This paper proposes a fast simulation method of freezing ice taking into account air bubbles. Our method introduces a physically-based calculation method of the sizes of air bubb...

We present a new technique for bi-scale material editing using Spherical Gaussians (SGs). To represent large-scale appearances, an effective BRDF that is the average reflectance of small-scale details is used. The effective BRDF is calculated from the integral of the product of the Bidirectional Visible Normal Distribution (BVNDF) and BRDFs of smal...

Pixel art is a kind of digital art that through per-pixel manipulation enables production of a diverse array of artistic images. In this paper, we present a new way for people to experience and express pixel art. Our digital art consists of a set of sticks made of acrylate resin, each of which refracts light from a parallel light source, in certain...

We propose an efficient rendering method for dynamic scenes under all-frequency environmental lighting. To render the surfaces of objects illuminated by distant environmental lighting, the triple product of the lighting, the visibility function and the BRDF is integrated at each shading point on the surfaces. Our method represents the environmental...

Real-time rendering of dynamic scenes illuminated by complex, all-frequency lighting with highly glossy BRDFs remains a challenging problem. Although several methods have been proposed to render dynamic scenes, these methods can not handle deformable objects [Zhou et al. 2005], all-frequency lighting [Ren et al. 2006; Nowrouzezahrai et al. 2009], o...

Photo‐realistic rendering of inhomogeneous participating media with light scattering in consideration is important in computer graphics, and is typically computed using Monte Carlo based methods. The key technique in such methods is the free path sampling, which is used for determining the distance (free path) between successive scattering events....

In the field of Computer Graphics (CG), applications such as movies and games benefit from realistic visualizations of atmospheric phenomena because realistic visualizations increase applications' attractiveness. Among the atmospheric phenomena, auroras are some of the most beautiful phenomena, which makes their visualization highly desirable for s...

Realistic rendering of participating media is one of the major subjects in computer graphics. Monte Carlo techniques are widely used for realistic rendering because they provide unbiased solutions, which converge to exact solutions. Methods based on Monte Carlo techniques generate a number of light paths, each of which consists of a set of randomly...

Interactive rendering under complex real world illumination is essential for many applications such as material design, lighting design, and virtual realities. For such applications, interactive manipulations of viewpoints, lighting, BRDFs, and positions of objects are beneficial to designers and users. This paper proposes a system that acquires co...

Abstract The visual simulation of natural phenomena has been widely studied. Although several methods have been proposed to simulate melting, the flows of meltwater drops on the surfaces of objects are not taken into account. In this paper, we propose a particle-based method for the simulation of the melting and freezing of ice objects and the inte...

Fast computation of multiple light reflections and scattering among complex objects is very important in photo-realistic rendering. This paper applies the plane-parallel scattering theory to the rendering of densely distributed objects such as hairs. We propose a simplified plane-parallel model that has very simple analytic solutions. This allows u...

A rendering system for interior scenes is proposed in this paper. The light reaches the interior scene, usually through small regions, such as windows or abat-jours, which we call portals. To provide a solution, suitable for rendering interior scenes with portals, we extend the traditional precomputed radiance transfer approaches. In our approach,...

Lighting simulation is very important in realistic image synthesis, and the simulation of subsurface scattering has recently attracted much attention. Although the dipole/multipole model has succeeded in creating realistic images, it is still difficult to deal with volumetric features in subsurface scattering, which is important when rendering opti...

This paper presents a BRDF modeling method, based on an inverse problem approach. Our method calculates BRDFs to match the appearance of the object specified by the user. By representing BRDFs by a linear com- bination of basis functions, outgoing radiances of the object surface can be represented using basis functions. The calculation of the desir...

Rendering scattering materials is an important issue in realistic rendering. This paper describes calculation and interpolation methods of BRDFs/BTDFs (Bidirectional Reflectance/Transmittance Distribution Functions) of scattering materials. We introduced the plane-parallel scattering theory, which enables us analytic calculation of BRDFs/BTDFs of u...

Particle-based simulations are widely used to simulate fluids. We present a real-time rendering method for the results of particle-based simulations of water. Tra- ditional approaches to visualize the results of particle- based simulations construct water surfaces that are usu- ally represented by polygons. To construct the water surfaces from the...

To render specular surfaces, reflections play an important role to enhance the realism. For concave surfaces, the effects of self-reflections that the surface reflects a part of the surface itself are necessary to create realistic images. This paper presents a real-time rendering of rigid specular surfaces taking into account self-reflections. In t...

Physically based fluid simulation is one of the most important research topics in computer graphics. Although many methods have been developed that use 3D or 2D grids to simulate fluids, there are few methodd for simulating fluid flows on surfaces. We present a real-time particle-based simulation method for the flows on surfaces. The surfaces are p...

In this paper, we propose a fast global illumination solution for interactive lighting design. Using our method, light sources and the viewpoint are movable, and the characteristics of materials can be modified (assuming low-frequency BRDF) during rendering. Our solution is based on particle tracing (a variation of photon mapping) and final gatheri...

In this paper, we propose an interactive rendering method for taking into account global illumination using light path precomputation and a hierarchical data structure for fast final gathering. Our method can render static scenes interactively allowing the user to move the viewpoint and the positions of local light sources. More-over, our method ca...

In this paper, we propose an interactive rendering method for taking into account global illumination using light path precomputation and a hierarchical data structure for fast final gathering. Our method can render static scenes interactively allowing the user to move the viewpoint and the positions of local light sources. Moreover, our method can...

Fast rendering of dynamic scenes taking into account global illumination is one of the most challenging tasks in computer graphics. This paper proposes a new precomputed radiance transfer (PRT) method for rendering dynamic scenes of rigid objects taking into account interreflections of light between surfaces with diffuse and glossy BRDFs. To comput...

In recent years, attention has been paid to particle-based fluid simu- lation, with several methods being developed to incorporate particle-based sim- ulation into CG animations. These methods reconstruct water surfaces that are usually represented by polygons. However, the computational cost of the surface reconstruction is quite high. Therefore,...

Dreams in High Fidelity is a painting that evolves. It was designed and rendered with the Electric Sheep screen-saver, a cyborg mind composed of 30,000 computers and people mediated by a genetic algorithm. Physically it consists of a small computer ...

We present a real-time rendering method of translucent materials such as marble for large 3D models. To render translucent objects, it is necessary to take into account the subsurface scattering of light. However, rendering translucent objects with the subsurface scattering takes long time. In our method, virtual points are set around the object un...

The importance of informal communication on the Internet has been increasing in recent years. Several systems for informal communication have been developed. These systems, however, require a particular server and/or specialized 3D contents. In this paper, we propose a system, named InCom , for informal communication in a 3D virtual environment...

Caustics are patterns of light focused by reflective or refractive objects. Because of their visually fascinating patterns, several methods have been developed to render caustics. We propose a method for the quick rendering of caustics formed by refracted and converged light through transparent objects. First, in the preprocess, we calculate sampli...

Rendering refractive caustics from transparent objects on opaque objects is computationally in- tensive. This paper presents a fast rendering technique for transparent objects and refractive caustics due to transparent objects on the opaque object. To calculate the intensities of caustics, we set virtual planes around the opaque object and store th...

People usually try to show themselves attractively, since attractive looks are generally preferred. We propose a new method for modifying facial data in order to improve facial beauty while retaining the original features as much as possible. Based on investigations into related work of facial attractiveness , the targets for modification in our me...

The importance of informal communication on the Internet has been increasing in recent years. Several systems for informal communication are currently available to the public. These systems, however, require a particular server and/or specialized 3D content. In this paper, we propose a system for informal communication in a 3D virtual environment....

Caustics are patterns of light formed by reflection or refraction of light from objects, and several methods have been developed to render caustics because of their visually beautiful patterns. This paper proposes a method for the rapid rendering of caustics formed by refracted light through transparent objects. First, a preprocess is used to gener...

In the field of computer graphics, simulation of physical phenomena is of great interest. We focus on the optical effects of soap bubbles. Soap bubbles have fascinating coloration and interesting physical properties. Therefore they are useful for the entertainment such as movies and games. Soap bubbles change their shapes by surface tension and ext...

The diffusion method is a good approximation inside the dense core of a cloud, but not at the more tenuous boundary regions. Also, it breaks down in regions where the density of scattering droplets is zero. We have enhanced it by using hardware cell projection volume rendering at cloud border voxels to account for the straight line light transport...

The diffusion method is a good approximation inside the dense core of a cloud, but not at the more tenuous boundary regions. Also, it breaks down in regions where the density of scattering droplets is zero. We have enhanced it by using hardware cell projection volume rendering at cloud border voxels to account for the straight line light transport...

The sky color is indispensable for the display of natural scenes in computer graphics. To render the photorealistic images of the sky, the calculation taking into account multiple scattering is necessary. However the calculation is so complex that enormous computational cost is required. Therefore, in this paper, we proposed a method using virtual...

In order to synthesize realistic images of scenes that include water surfaces, the rendering of optical effectscaused by waves on the water surface, such as caustics and reflection, is necessary. However, rendering causticsis quite complex and time-consuming. In recent years, the performance of graphics hardware has made significantprogress. This f...

We present a fast volume rendering technique for sea surfaces taking into account second order scattering using graphics hardware. To generate realistic images of the sea surfaces, accurate simulation of light transport within water is necessary. In particular, multiple scattering due to particles in the water plays an important role in creating re...

The display of realistic natural scenes is one of the most important research areas in computer graphics. Therendering of water is one of the essential components. This paper proposes an efficient method for renderingimages of scenes within water. For underwater scenery, the shafts of light and caustics are attractive and importantelements. However...

The display of realistic natural scenes is one of the most important research areas in computer graphics. The rendering of water is one of the essential components. The paper proposes an efficient method for rendering images of scenes within water. For underwater scenery, the shafts of light and caustics are attractive and important elements. Howev...

This paper presents a real-time rendering method of ob- jects coated with multilayer thin films. To render objects coated with multilayer thin films, the products of the spec- tral power distributions (SPDs) of the composite reflectivity, the incident light, and the color matching function are inte- grated. To calculate this integration numerically...

In this paper, we focus on simulation of magnetic fluids. Magnetic fluids behave as both fluids and as magnetic bodies, and these characteristics allow them to generate 'spike-like' shapes along a magnetic field. Magnetic fluids are popular materials for use in works of art. Our goal is to simulate such works of art. In the field of electromagnetic...