Fujiichi Yoshimoto

Data fitting with a spline using a real-coded genetic algorithm

To obtain a good approximation for data fitting with a spline, frequently we have to deal with knots as variables. The problem to be solved then becomes a continuous nonlinear and multivariate optimization problem with many local optima. Therefore, it is difficult to obtain the global optimum. In this paper, we propose a method for solving this problem by using a real-coded genetic algorithm. Our method can treat not only data with a smooth underlying function, but also data with an underlying function having discontinuous points and/or cusps. We search for the best model among candidate models by using the Bayes Information Criterion (BIC). With this, we can appropriately determine the number and locations of knots automatically and simultaneously. Five examples of data fitting are given to show the performance of our method.

Precomputed radiance transfer for dynamic scenes taking into account light interreflection

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 compute the interreflections of light between rigid objects, we consider the objects as secondary light sources. We represent the intensity distributions on the surface of the objects with a linear combination of basis functions. We then calculate a component of the irradiance per basis function at each vertex of the object when illuminated by the secondary light source. We call this component of the irradiance, the basis irradiance. The irradiance is represented with a linear combination of the basis irradiances, which are computed efficiently at run-time by using a PRT technique. By using the basis irradiance, the calculation of multiple-bounce interreflected light is simplified and can be evaluated very quickly. We demonstrate the real-time rendering of dynamic scenes for low-frequency lighting and rendering for all-frequency lighting at interactive frame rates.

An educational tool for basic techniques in beginner's pencil drawing

A picture is one of important research subjects in order to make our life spiritually rich. Most studies on pictures, however, only propose some substitute functions of actual drawing or painting materials. There is no system that evaluates pictures drawn by users and gives advice about them. We propose a learning support system for basic techniques in beginners pencil drawing. The proposed system receives a subject (motif) data set and an image of users sketch and returns advice to the user. The system is composed of the four subsystems: feature extraction of motifs, feature extraction of sketches, error identification, and generation and presentation of advice. We developed and experimented a prototype system limited to treat a basic motif and some principal advice. As a result, the validity of the proposed system was confirmed.

A learning support system for beginners in pencil drawing

A picture is one of important research subjects to make our life spiritually rich. Most studies on pictures, however, only propose some substitute functions of actual drawing or painting materials. There is no system that evaluates pictures drawn by users and gives advice about them. We propose a learning support system of beginners pencil drawing that is the basis of pictures. Our system receives a motif data set and a users sketch image, and returns advice to the user. The processing is composed of the four functions: feature extraction of motifs, feature extraction of sketches, error identification, and generation and presentation of advice. We developed and experimented a prototype system limited to treat a basic motif and principal advice. As a result, the validity of the proposed system was confirmed.

Real-Time rendering of point based water surfaces

In recent years, attention has been paid to particle-based fluid simulation, with several methods being developed to incorporate particle-based simulation 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, it is difficult to render the result of the particle-based simulation at interactive frame rates. To address this, we present a real-time method for rendering water surfaces resulting from particle-based simulation. We present an efficient GPU accelerated surface reconstruction method from particles, sampling the water surface point by point. In addition to rendering the point based water surfaces, the use of the GPU permits efficient simulation of optical effects such as refraction, reflection, and caustics.

Sketch learning environment based on drawing skill analysis

Skill knowledge is important human knowledge as well as symbolic knowledge. Definition of skill knowledge is knowledge on high level technique that human acquire through repeated training. Skill knowledge is needed for arts, sports and crafts. It concerns human body structure, muscles, and joints. Also, skill knowledge concerns process of human interaction with objects, namely, recognition and action. There are many researches on learning support system for describable knowledge, such as mathematics, physics, grammar, etc. However, there is few pieces of research on learning support system for skill such as arts and sports. This paper analyses skills and generalize skill features. Then we describe problems to diagnose skill errors. After that, we introduce a learning support system for sketch as an example of a skill learning support environment.

Precomputed radiance transfer for dynamic scenes with diffuse interreflection

Kei Iwasaki∗ Wakayama University Yoshinori Dobashi Hokkaido University Naoki Tamura The University of Tokyo Henry Johan† The University of Tokyo Fujiichi Yoshimoto Wakayama University Tomoyuki Nishita The University of Tokyo

A Method for Fast Rendering of Caustics from Refraction by Transparent Objects

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 sampling rays incident on each vertex of the object, and trace the rays until they leave the object taking refraction into account. The position and direction of each ray that finally transmits the transparent object are obtained and stored in a lookup table. Next, in the rendering process, when the object is illuminated, the positions and directions of the rays leaving the object are calculated using the lookup table. This makes it possible to render refractive caustics due to transparent objects at interactive frame rates, allowing us to change the light position and direction, and translate and rotate the object.

A rapid rendering method for caustics arising from refraction by transparent objects

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 generate sampling rays incident on each vertex of the object, and, taking refraction into account, to trace the rays until they leave the object. The position and direction of each ray that finally leaves the transparent object are obtained and stored in a lookup table. Next, in the rendering process, when the object is illuminated, the position and direction of the rays leaving the object are calculated using the lookup table. This makes it possible to render refractive caustics due to transparent objects at interactive frame rates even if the direction of the light changes and the object is translated or rotated.

The proposal of the technique of error visualization for a learner's pencil drawing

In a pencil drawing class, a teacher explains often the differences between a drawing and a motif by many ways; even so, it is difficult for most learners to understand the existence of errors in his/her drawing. When a learner watches the 3D model of his/her drawing from appropriate viewpoints, he/she is immediately aware of the errors. This paper describes the technique of error visualization from a learners erroneous drawing. We developed a drawing advice system that consists of a 3D model converter from a 2D image and an evaluation function to estimate the effect of the 3D model. We designed a geometrical formula that expresses the relation between the geometrical feature and the error expression in the teachers advice.