Tomoyuki Nishita

Hiroshima Shudo University · Econmic Sience

This paper presents intersection test and detection of the minimum distance between rational surfaces/curves and spheres (ellipsoids or Metaballs). We discuss an effective method of arranging/editing parts with curved surfaces. The proposed method is applicable to metaballs/bounding spheres for triangle (or polygonal) meshes of curved surfaces not...

The computational cost for creating realistic fluid animations by numerical simulation is generally expensive. In digital production environments, existing precomputed fluid animations are often reused for different scenes in order to reduce the cost of creating scenes containing fluids. However, applying the same animation to different scenes ofte...

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...

Generating realistic fluid simulations remains computationally expensive, and animators can expend enormous effort trying to achieve a desired motion. To reduce such costs, several methods have been developed in which high-resolution turbulence is synthesized as a post process. Since global motion can then be obtained using a fast, low-resolution s...

The computational cost of physically-based fluid simulation for generating realistic animations is expensive. Therefore, it takes a long time for an animator to create the desired animation. To reduce such costs, several methods have been developed that employ an approach in which turbulence is synthesized as a post process. Since, with this approa...

We propose a hybrid smoothed particle hydrodynamics solver for efficientlysimulating incompressible fluids using an interface handling method for boundary conditions in the pressure Poisson equation. We blend particle density computed with one smooth and one spiky kernel to improve the robustness against both fluid–fluid and fluid–solid collisions....

Visual simulation of fire plays an important role in many applications, such as movies and computer games. In these applications, artists are often requested to synthesize realistic fire with a particular behavior. To meet such requirement, we present a feedback control method for fire simulations. The user can design the shape of fire by placing a...

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 computational cost for creating realistic fluid animations by simulation is generally very expensive. In digital production environment, existing precomputed fluid animations are often reused for different scenes in order to reduce the cost for creating scenes containing fluids. However, applying same animations to different scenes produces una...

Fast realistic rendering of objects in scattering media is still a challenging topic in computer graphics. In presence of participating media, a light beam is repeatedly scattered by media particles, changing direction and getting spread out. Explicitly evaluating this beam distribution would enable efficient simulation of multiple scattering event...

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...

In this paper, we develop a method for synthesizing desired flow fields by combining existing multiple flow fields. Our system allows the user to specify arbitrary regions of the precomputed flow fields and combine them to synthesize a new flow field. In order to maintain plausible physical behavior, we ensure the incompressibility for the combined...

Building LEGO sculptures requires accounting for the target object's shape, colors, and stability. In particular, finding a good layout of LEGO bricks that prevents the sculpture from collapsing ( due to its own weight) is usually challenging, and it becomes increasingly difficult as the target object becomes larger or more complex. We devise a for...

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...

We propose a stable and efficient particle-based method for simulating highly viscous fluids that can generate coiling and buckling phenomena and handle variable viscosity. In contrast to previous methods that use explicit integration, our method uses an implicit formulation to improve the robustness of viscosity integration, therefore enabling use...

We propose a particle-based hybrid method for simulating volume preserving viscoelastic fluids with large deformations. Our method combines smoothed particle hydrodynamics (SPH) and position-based dynamics (PBD) to approximate the dynamics of viscoelastic fluids. While preserving their volumes using SPH, we exploit an idea of PBD and correct partic...

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...

Viscous fluids are ubiquitous, and reproducing their damped motions has been in demand for many applications. The most prevalent approach to simulating viscous fluids is based on the Navier-Stokes equations and necessitates viscosity integration. However, to simulate viscous fluids in a numerically stable manner, using explicit viscosity integratio...

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...

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 hair simulation, hair collision handling plays an important role to make hair look realistic; hair collision maintains the volume of hair. Without hair collision, hair would appear unnaturally flat.

We propose a simple yet flexible method for computing droplet shapes on the surface of an object, given the two dimensional outlines (footprints) of the droplets. The user specifies the desired outline on a solid base model, and a droplet with a plausible shape positioned on the object exactly within the outline is automatically generated. Our meth...

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...

Photo-realistic rendering of participating media, such as steam, water, fire, and smoke, is an important research topic in the computer graphics field. We present a fast and physically based method for rendering participating media based on the progressive photon beams method. For this, we propose a new version using adaptive free path sampling tec...

In this paper, we propose a simple method for simulating the generation, growth and motion of bubbles in carbonated water. Bubbles are known to be generated at small air pockets on the surfaces of objects, such as a glass or a stirrer, and on the microscopic dusts in carbonated water. The number of bubbles and their growth rates differ according to...

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...

Clouds play an important role in creating realistic images of outdoor scenes. Many methods have therefore been proposed for displaying realistic clouds. However, the realism of the resulting images depends on many parameters used to render them and it is often difficult to adjust those parameters manually. This paper proposes a method for addressin...

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...

There is considerable recent progress in hair simulations, driven by the high demands in computer animated movies. However, capturing the complex interactions between hair and water is still relatively in its infancy. Such interactions are best modeled as those between water and an anisotropic permeable medium as water can flow into and out of the...

Animation of water drops on a windshield is used as a special effect in advanced driving games and simulators. Existing water droplet animation methods trace the trajectories of the droplets on the glass taking into account the hydrophilic or water-attracting nature of the glass material. Meanwhile, in the automobile industry, usage of hydrophobic...

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...

String-like objects in our daily lives, for example shoelaces, threads, rubber cords, plastic fiber and spaghetti, have a wide variety of materials. Such string-like objects also exhibit interesting behaviors such as twisting, tearing (by stretching or twisting), and bouncing back when pulled and released. In this paper, we present a method that en...

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...

String-like objects in our daily lives including shoelaces, threads and rubber cords exhibit interesting behaviors such as twisting, tearing and bouncing back when pulled and released. In this paper, we present a method that enables these behaviors in traditional string simulation methods that explicitly represent a string by particles and segments...

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....

Image blur caused by object motion attenuates high frequency content of images, making post‐capture deblurring an ill‐posed problem. The recoverable frequency band quickly becomes narrower for faster object motion as high frequencies are severely attenuated and virtually lost. This paper proposes to translate a camera sensor circularly about the op...

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...

We present a fast algorithm for reducing the undesired distortions (e.g., bending of straight lines) that often appear in wide-angle images especially taken with fisheye lenses. Our method allows the user to intuitively specify curves to be straightened by using quadratic control curves, and then automatically warps the image based on moving least-...

Sampling patterns with a blue noise distribution are widely used in many areas of computer graphics, yet their efficient generation remains a difficult problem. We propose a method to generate point sets with a blue noise distribution using a deterministic algorithm with no preprocessing. We insert each new sample at the center of the largest empty...

We propose an efficient method based on physical laws to model phenomena near the surface of the sun, which is known as the solar photosphere. In the field of astron-omy, some physical models have been developed to simulate the sun's turbulence. Most of the previous models are difficult to be applied in the making of CG images since they re-quire a...

Non-Photorealistic Rendering (NPR), whose aim is to create artistic style images, is one of the important research topics in computer graphics. One example of NPR is an art form called ASCII art which represents pictures using charac-ter strings. ASCII art is commonly used in media that cannot display images or mainly use text, such as e-mail and b...

In recent years, many line drawing algorithms have been proposed for 3D shape depiction. One common drawback is that these algorithms draw only part of the necessary lines for fully depicting the shape. Cole et al. ¹⁾ have shown that these algorithms can be complementary to each other. Based on that, in this paper, we combine the previous algorithm...

One-dimensional deformable objects or elastic rods are widely used to represent threads, hair strands and elastic ropes in computer graphics. Such an object has the bending, stretching and twisting behaviors which are difficult to handle. To simulate deformable objects, a simple method called Lattice Shape Matching (LSM) [Rivers and James 2007] was...

We present a multi touch display prototype based on optical tracking on commonly available LCD display. We describe several possible hardware configurations and discuss their problems. The output from this device is a video sequence that is processed to recognize the gestures. We propose a video preprocessing of input sequence and various applicati...

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...

This paper proposes a method for displaying images at the fovea of the retina taking visual acuity into account. Previous research has shown that a point light source projected onto the retina forms an ellipse, which can be computed with wavefront tracing from each point in space. We propose a novel concept using conoid tracing, with which we can a...

Animations of hair dynamics greatly enrich the visual attractiveness of human characters. Traditional simulation techniques handle hair as clumps or continuum for efficiency; however, the visual quality is limited because they cannot represent the fine-scale motion of individual hair strands. Although a recent mass-spring approach tackled the probl...

This paper proposes the extraction of a skeleton and skin-ning weights from a given mesh, describes how to store computed data in Collada 1.5 and use it for an animation. Firstly, the mesh is contracted using constrained Laplacian smoothing in a few iterations. Few vertices from the con-tracted mesh are chosen as control points. Multiple edges are...

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 Given a complete unoriented point set, we propose a binary orientation tree (BOT) for volume and surface representation, which roughly splits the space into the interior and exterior regions with respect to the input point set. The BOTs are constructed by performing a traditional octree subdivision technique while the corners of each cell...

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...

Polygonal meshes are widely used to represent the shape of 3D objects and the generation of multi-resolution models has been a significant research topic in computer graphics. In this paper, we demonstrate how to generate multi-resolution models through 2D image processing techniques. The goal of generating multi-resolution models is accomplished b...

Fur is present in most mammals which are common characters in both movies and video-games, and it is important to model and render fur both realistically and quickly. When the objective is real-time performance, fur is usually represented by texture layers (or 3D textures), which limits the dynamic characteristics of fur when compared with methods...

In the field of computer graphics, simulation of fluids, including avalanches, is an important research topic. In this paper, we propose a method to simulate a kind of avalanche, mixed-motion avalanche, which is usually large and travels down the slope fast, often resulting in impressive visual effects. The mixed-motion avalanche consists of snow s...

This paper presents an interactive system for realistic visualization of earth-scale clouds. Realistic images can be generated at interactive frame rates while the viewpoint and the sunlight directions can be changed interactively. The realistic display of earth-scale clouds requires us to render large volume data representing the density distribut...

Abstract This paper presents a novel framework for elliptical weighted average (EWA) surface splatting with time-varying scenes. We extend the theoretical basis of the original framework by replacing the 2D surface reconstruction filters by 3D kernels which unify the spatial and temporal component of moving objects. Based on the newly derived mathe...

In computer graphics animation, animation tools are required for fluid-like motions which are controllable by users or animator, since applying the techniques to commercial animations such as advertisement and film. Many developments have been proposed to model controllable fluid simulation with the need in realistic motion, robustness, adaptation,...

In computer graphics animation, animation tools are required for fluid-like motions which are controllable by users or animator, since applying the techniques to commercial animations such as advertisement and film. Many developments have been proposed to model controllable fluid simulation with the need in realistic motion, robustness, adaptation,...

In traditional image composition methods for cutting out an object (source object) from an image (source image) and pasting it onto another image (target image), users have to segment a foreground object (target object) in a target image or cut out the part of the source object when they want to partially hide a source object behind it. While recen...

Glare effect is widely used in games and entertainment field as a computer graphics special effect. In this paper, we propose a method to render glare phenomena with high reproduction fidelity and introduce its application to lamp design. Our method simulates a diffraction phenomenon which takes place in the human eye visual system, and pre-compute...

In traditional image composition methods for cutting out a source object from a source image and pasting it onto a target image, users have to segment a foreground object in a target image when they want to partially hide a source object behind it. While recent image editing tools greatly facilitate segmentation operations, it can be tedious to seg...

Surface reconstruction is a critical stage in the 3D data acquisition and model creation system. Most existing reconstruction algorithms are designed for oriented data, i.e. point sets with surface normals. However, in some applications, explicit orientation information may not be available, e.g. Shape from Contour (SfC). Besides, the point sets re...

Abstract Woven cloth can commonly be seen in daily life and also in animation. Unless prevented in some way, woven cloth usually frays at the edges. However, in computer graphics, woven cloth is typically modeled as a continuum sheet, which is not suitable for representing frays. This paper proposes a model that allows yarn movement and slippage du...

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,...

In this extended abstract, we present a system that allows the user to animate character images in 3D space by applying an existed 3D character model with motion data. The character model with skeleton rigged is used as a template model to fit the silhouette of the character image. After assigning some corresponding points between the character ima...

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...

SUMMARY We propose an interactive method for assisting the coloring process of 2D hand-drawn animated cartoons. It segments input frames (each hand-drawn drawing of the cartoon) into regions (areas surrounded by closed lines. E.g. the head, the hands) extracts their features, and then matches the regions between frames, allowing the user to fix col...

This paper presents a fast method that computes deformations with fracturing of an object using a hierarchical lattice. Our method allows numerically stable computation based on so-called shape matching. During the simulation, the deformed shape of the object and the condition of fracturing are used to determine the appropriate detail level in the...

Simulating the destruction of objects due to collisions has many applications in computer graphics. Previous methods on the destruction of objects perform physically-based simulation of the fracture of objects into relatively large size fragments. However, if we observe the process of the destruction of objects, we can see that dust and fine debris...

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...

This paper presents an interactive system for realistic visualization of earth-scale clouds. Realistic images can be generated at interactive frame rates while the viewpoint and the sunlight directions can be changed interac- tively. The realistic display of earth-scale clouds requires us to render large volume data representing the density distrib...

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...