Cell sorting by differential adhesion is one of the basic mechanisms explaining spatial organization of neurons in early stage brain development of fruit flies. The columnar arrangements of neurons determine the large-scale patterns in the fly visual center. Experimental studies indicate that hexagonal configurations regularly appear in the fly compound eye, which is connected to the visual center by photoreceptor axons, while tetragonal configurations can be induced in mutants. We need a mathematical framework to study the mechanisms of such a transition between hexagonal and tetragonal arrangements. Here, we propose a new mathematical model based on macroscopic approximations of agent-based models that produces a similar behavior changing from hexagonal to tetragonal steady configurations when medium-range repulsion and longer-range attraction between individuals are incorporated in previous successful models for cell sorting based on adhesion and volume constraints. We analyze the angular configurations of these patterns based on angle summary statistics and compare between experimental data and parameter fitted ARA (Adhesion-Repulsion-Attraction) models showing that intermediate patterns between hexagonal and tetragonal configuration are common in experimental data as well as in our ARA mathematical model. Our studies indicate an overall qualitative agreement of ARA models in tile patterning and pave the way for their quantitative studies. Our study opens up a new avenue to explore tile pattern transitions, found not only in the column arrangement in the brain, but also in the other related biological processes.

This paper describes the analysis of defocus information when a finger touching a virtual keyboard by using DCT (Discrete Cosine Transform) coefficient without detecting 3D position (especially exact depth value) of thr finger. We use 2 cameras and a half mirror to get the images of the finger with same optical axis. The focal length of the two cameras are slightly different. We can know the finger touching the virtual keyboard when the finger is in the middle of the two focal length from the defocus information, because the position of the virtual keyboard is in the middle of the two focal position where the defocus information of the two cameras are same. Previous work of a virtual keyboard is realized by detecting the feature point of the finger at first. After that the finger position and the depth are checked if they are same to the position and the depth of the keyboard. A problem of the previous virtual keyboard is 3D point of the finger (feature point or edge, small region) should be detected. This is very time consuming. We overcome this problem by comparing the defocus information of the finger in the key area of virtual keyboard on the 2 images captured by the two cameras. In this paper we describe the optical system of the virtual keyboard and the resolution of the depth of the finger. Experimental result make it clear that middle range of the DCT coefficients is effective for detecting the finger. In our system, the finger touch is detected by comparing the DCT coefficients of the 2 images. The minimum distance of the detectable finger is depended on the diameter and the focal length of the lens, the resolution of the image sensor. We formulate this theoretical minimum distance and verify it by experiment. Besides finger, our system can also be generalized to detect other object touching the keyboard or not.

We have developed a haptic visualization system for molecular docking applications in education. Although molecular docking is a 3D phenomenon, desktop or laptop PCs require a mouse as a common interface, which limits manipulations to 2D. Our system applies 2D lateral forces to haptic feedback using the SPIDAR-mouse and maps the surface of a 3D object to the 2D plane. The SPIDAR-mouse is a simple haptic device with 2D lateral forces, which is considered suitable for educational environments. In this paper, we discuss the haptic visualization techniques using 2D development view and a processing method for generating cuts on the 3D object surface for a prototype of our system. Our visualization system enables users to intuitively interact with a 3D object using 2D lateral force feedback.

There is a vast development and significant involvement of haptic interfaces in the world for virtual reality applications. In this paper, we introduce the research and development of desktop versions of friendly human interface called SPIDAR haptic interfaces on the Sato Makoto Laboratory in the Tokyo Institute of Technology. This haptic interface can be used in various types of virtual reality applications for simple pick and place tasks to more complicated physical interactions in virtual worlds.

A haptic visualization system was made with the SPIDAR-mouse for 2D lateral force feedback in molecular docking. An educational environment requires factors such as easy installation, low cost, and reasonable performance, which the SPIDAR-mouse can provide. However, it limits the representation of force to 2D, even though the molecular interaction includes 3D phenomena. Our approach to the solution is to map the surface of 3D molecules to the 2D plane. The haptic rendering is done by calculating forces with the 2D map, which largely reduces the computational cost. The molecular interaction based on the electro-static potential and conformational properties is displayed with the 2D lateral force feedback using the SPIDAR-mouse.

A visual analysis method for finding a variety of human networks in chronicles on the basis of different viewpoints is proposed. A vast amount of human experience records is stored all over the world. For understanding and using such chronicles effectively, it is necessary to find several relations embedded in records. In this article, we propose a chronicle analysis tool (CAT), which provides several views of records from different viewpoints. For such purpose, we introduce the notion of chronicle data and a visual analysis framework for embedded relations in chronicles. On the basis of these notions, we describe a chronicle analysis tool and show a variety of historical human networks from different viewpoints as examples of its implementation.

This paper proposes a pen-based interaction system with 2D co-located haptic and visual feedback for physics education. The system combines a 3DOF pen-based planar haptic device and simulated 2D physical world based on physical engine Box 2D and 2D game engine HGE. The inputs of haptic device are translation and rotation of pen tip and the outputs are translational and rotational force displayed at pen tip. In addition, visual display and haptic display are coincident and well integrated. With this system, user can create and design simulated physical world by drawing, selecting, moving or rotating objects on screen and setting their physical properties in a natural and intuitive way. This system provides an entertaining and cartoony tool for designing and carrying out physics experiments, and will greatly promote students' learning interest and creativity.

In this paper, we propose a technique for a high quality haptic display working with a low update rate rigid body dynamics simulator. The proposed method uses two dynamics simulators. One has a low update rate for the whole virtual world and the other has a high update rate for the neighboring objects of the haptic pointer. In addition, the method calculates accelerance matrices of neighboring objects with regard to the contact forces added to these objects. We carried out a simulation and an experiment to check the effectiveness of the proposed method.

This paper introduces a method for bridging topics designed to facilitate generating stories over documents. First, we present a method for topic extraction based on narrative structure with k-means algorithm. We then model the story generation process and present a method for finding a bridge document between two documents.

We present a method to extract salient regions in natural images based on local extrema. Behavioral and physiological studies on human vision indicate that the peripheral vision has an important role to get salient regions into the fovea to obtain detailed information from the environment. Modeling of the peripheral is the key to create a salient region extraction method with the behavioral plausibility. To extract salient regions in a natural image, we focus on the multiresolutional 2-D distribution of local extrema. Local extrema detect regions in the image that are either brighter or darker than the surroundings. They will provide useful information to extract salient regions regardless of the image resolution. As for the function of human vision, an image is more blurred in more peripheral. So we model the peripheral using scale-space image representation. In this study, we define the saliency based on the stability of local extrema on scale-space and create a method to extract salient regions. Comparing the human map of fixations, we ensure that our method successfully extracts salient regions.

We are developing a software-execution framework based on an octo-core chip multiprocessor named RP2 and an automatic multigrain-parallelizing compiler named OSCAR. The main purpose of this framework is to maintain good speed scalability and power efficiency over the number of processor cores under severe hardware restrictions for embedded use. Key to the speed scalability is reduction of a communication overhead with parallelized tasks. A data-categorization scheme enables small-overhead cache-coherency maintenance by using directives and instructions from the compiler. In this scheme, the number of cache-flushing time is minimized and parallelized tasks are quickly synchronized by using flags in local memory. As regards power efficiency, to reduce power consumption, power supply to processor cores waiting for other cores is timely and frequently cut off, even in the middle of an application, by using a timely-power- gating scheme. In this scheme, to achieve quick mode transition between "NORMAL" mode and "RESUME POWEROFF" mode, register values of the processor core are stored in core-local memory, which is active even in "RESUME POWEROFF" mode and can be accessed in one or two clock cycles. Measured speed and power of an application show good speed scalability in execution time and high power efficiency, simultaneously. In the case of a secure AAC-LC encoding program, execution speed when eight processor cores are used can be increased by 4.85 times compared to that of sequential execution. Moreover, power consumption under the same condition can be reduced by 51.0% by parallelizing and timely-power gating. The time for mode transition is less than 20 micro seconds, which is only 2.5% of the "RESUME POWER-OFF" period.

Sometimes, mirrors provide illusions that distort physical laws. In these methods, the illusions become "real" as your visual, tactile, and auditory senses are immersed in the world inside the mirror. Our methods allows you to experience a mirror illusion through three modalities of feedback (visual, haptic, and auditory) and perceive a boundary less transition between the real world and the world inside the mirror. This approach is expected to open new possibilities for using mirrors in the fields of media art or virtual reality.

Abstract Various forms of art and entertainment involve many different characters, and advances in human interfaces have necessitated physical interactions in order to develop an improved sense of reality. In this paper we propose a method for generating the motions of characters using multidimensional keyframe animation in parallel with real‐time physical simulation. The method generates characters capable of physical interaction, and also allows animators to use traditional methods for designing character motion. We have implemented the system and confirmed its effectiveness experimentally.

This paper addresses the problem of clustering objects located and correlated geographically and containing multiple attributes. For the clustering problem, it is necessary to consider both the similarities of the attributes and the spatial dependencies of the objects. A new clustering framework using hidden Markov random fields (HMRFs) and Gaussian distributions and new potential models of HMRFs for irregularly located geospatial objects are proposed in this paper. Experimental results for systematic data and two real-world data showed the availability of the proposed algorithms.

We attempted to produce an environment for education. Subjects such as mathematics or sciences are usually studied on a desk in a classroom. Our research goal is to allow students to study scientific contents more viscerally than existing studying methods by haptic interaction. To construct the environment, we have to make a user-friendly haptic interface. The study is described in two parts. The first part is defining what a useful haptic interface is. In this part, we focused on the grip of a haptic interface. SPIDAR-G is a haptic interface, which is manipulated by a grip with 8 strings.. Grip size is an important parameter for usability. We have found an optimal sphere size through SPIDAR-G usability testing. The other part is defining how teachers can use the interactive system with haptic interaction as a teaching aid. In this part , we focused on the interaction between two water molecules. First, we constructed an environment to feel Van der Waals force as well as electrostatic force with haptic interaction. Then, we observe the effectiveness of the environment when used by a class of students.

In this paper, we propose a new animation creation process, based on the teacher-student concept. You are the teacher and want to teach someone a performance. First you show the student how to perform an action, you tell him "do like me". Then you correct his posture by moving with hands his arms, his torso, feet position and so forth by saying to him "do like this". To show the virtual human a motion, the user use motion capture. He may check easily the result in a human scale immersive environment. Then he finds the part of the motion he wants to correct. He edits the motion with his hands like in the real world using a two-handed haptic device. Thus the user can perform motion editing in an intuitive and natural way, and achieve both actor performance and animator task in a unified environment.

We create a framework for physical interaction with virtual human. The virtual human reacts to the input of the user in realtime. The virtual human has an ocular system model, which mimics human ocular system, to generate natural and human-like gaze motions and to create inputs for the cognitive model of the virtual human. The visual input for virtual human is generated from the dynamics simulator for the virtual world. The gaze target is chosen by vying of bottom-up and top-down attentions. The motion controller for the eyes and head is based on observations and models of human gaze motion. We create a virtual boxing game as an application of proposed framework. Proposed framework succeeds to create natural gaze reaction. In addition, by changing the balance of the bottom-up and top-down attention, looks of concentration of the virtual human can be tuned.

In this study, we achieved predictable control of a wheelchair by changing the existing mapping method of the joystick, which considers the consecutive operations of a motor of a wheelchair, to a new mapping method that corresponds to the internal model of a human being. Since the existing method uses the polar coordinate system, it is not easy at all to use this method to predict either the direction of motion or the operating order for changing the position of the wheelchair according to the requirements of an operator. In order to improve the embodiment, we divided the existing joystick mapping method into two degrees of freedom-one in the vertical axis that can control the velocity and the other, in the horizontal axis for direction control. Based on this division, we implemented a wheelchair model that can be controlled by the electromyography (EMG) signal from the neck and the arm muscles of an operator. This was achieved by mapping the divided degrees of freedom onto the degrees of freedom of the neck and arm of the operator. In this case, since the operator controls the direction of motion by the joint of his/her neck, he/she can move the wheelchair in the desired direction; thus, a more intuitive human interface is implemented.

One of the great abilities of the central nervous system (CNS) is that it can learn by itself how to control our body to execute required tasks. Although several motor control models have been proposed to explain well-learned arm reaching movements, those models do not fully consider how the CNS learns to control our body. In this paper, we propose a new motor control model that can learn to generate accurate reaching movements without prior knowledge of arm dynamics. In our model, the control law is learned in a trial-and-error manner using the reward signal. We focus on point-to-point arm reaching task in the sagittal plane and show that accurate reaching movements toward any given point can be learned and generated by our model. Furthermore, the model can predict human subjects' hand trajectories without specifying desired trajectories.

Haptic interfaces enable us to interact with a virtual world using our sense of touch. This paper presents a method for realizing haptic interaction with water. Our method displays forces acting on rigid objects due to water with a high frame rate (500 Hz). To achieve this, we present a fast method for simulating the dynamics of water. We decompose the dynamics into two parts. One is a linear flow expressed by a wave equation used to compute water waves. The other is a more complex and non-linear flow around the object. The fluid forces due to the non-linear flow is precomputed by solving Navier-Stokes equations, and stored in a database, named the Fluid Resistance Map. The precomputed non-linear flow and the linear flow are combined to compute the forces due to water.

We have proposed a human-scale interaction system (i.e. reactive virtual human system) with haptic sensation. This system is composed of a wire-based haptic interface and an immersive virtual environment (VE). Based on the framework, we realized virtual catch ball that a user can play a virtual human with a feeling of contacting real ball. To make a database of virtual human's natural reaction, we implemented reactive motion capture system that can capture movements with physical reaction in close interpersonal engagements. In this paper, we further show the system's extended function that new motions can reflect on virtual human's behavioral structure by an on-line motion capture. It will be a practical way to produce various motion patterns during playing, and to enforce virtual human's adaptive function.

The virtual reality (VR) technology has been used as the application of architectural presentation or simulation tool in the field of industry. The high immersion and intuitive visual information are the great merits of design evaluation or environmental simulation when we are using the virtual environments. But the distortion of distance perception in VR is still a big problem when the accuracy of distance presentation is strictly required. In this paper, we have carried out some experiments about distance estimation in the immersive virtual environments to verify the factors and their influence. We made a hypothesis that the lack of the information for the user in VR causes the different distance estimation from the real world because users are usually comfortable with moving fast and long distance in VR environments. So, we carried out basic experiment to prove our hypothesis that the lack of information makes subjects estimate the walked distance in VR shorter compared with the same distance in real. Also, among the factors that probably affect the distance estimation in VR, we verified the influence of the image resolution. The influence of resolution degradation of image on the distance estimation was verified with the condition of static and dynamic images. The results showed that the resolution has deep relation with the distance estimation. For example, the subject underestimated the distance at the lower resolution condition. We also find the methods of the making the lower resolution image could affects on the visual perception of subjects.

Many immersive displays developed in previous researches are strongly influenced by the design concept of the CAVE which is the origin of the immersive displays. We propose a novel multiprojector display for immersive virtual environments. Our system named "D-vision'' has a hybrid curved screen which consist of differently shaped surface elements that are partial surfaces of such objects as planes, spheres, cylinders and tori. 24 PCs and projectors generate high-quality stereoscopic images. Our rendering algorithm using our original image processing hardware and commodity 3D graphics hardware realizes seamless and nondistorted projection on the hybrid screen. The D-vision also has a human-scale haptic and locomotion interface by which the users of the D-vision can walk with their own foot and interact with virtual objects through their own hands. We show an overview of the D-vision and technologies used for the human-scale haptic- and locomotion interfaces.

In this paper, our initial work on the use of visualization and virtual reality for education especially for providing three-dimensional concepts of molecular structure was presented. Our system is composed of a hybrid screen, multi-projectors, PC cluster, 6DOF haptic device etc. It offers a channel to reach into the molecular space in an immersive environment, allows user to employ an intuitive 6DOF haptic device Spidar-G to control the perspective. For educators, it can serve as a good instructional aid for helping students to understand molecular structure through effective visual representation and interactive manipulation.

Abstract This paper proposes a new method for real‐time rigid body simulations for haptic interactions based on a penalty method regarding contact volume. Analytical methods for calculation of contact forces require too much time to maintain fast update rates for haptic controls. In addition, they prohibit direct connection of haptic interfaces. Penalty methods, which employ spring‐damper models for calculation of contact forces, offer a very rapid rate of iterations. In addition, they permit direct connection of haptic interfaces. Penalty methods are good for haptic interactions. However, previous penalty methods do not regard distribution of contact forces over the contact area. For that reason, they can't calculate normal and friction forces on face‐face contacts correctly. We propose a distributed spring‐damper model on a contact area to solve these problems. We analyze three‐dimensional geometries of the intersecting portion on the polyhedral objects. Then, we integrate forces and torques of distributed spring‐damper models. We implement a proposed simulator and compare it with a point‐based penalty method and constraint method. The comparison shows that the proposed simulator improves accuracy of the simulation of face‐face contact and friction forces and the simulation speed. In addition, we attach a six degree‐of‐freedom (6‐DOF) haptic interface to the simulator. Users can feel 6‐DOF force feedback and input 6‐DOF motions. Categories and Subject Descriptors (according to ACM CCS): I.6.5 [Model Development]: Modeling methodologies, H.5.2 [User Interfaces]: Haptic I/O, I.3.6 [Methodology and Techniques]: Interaction techniques

This paper proposes a new approach for adding haptic feedback on a workbench. The integration of a stringed haptic device is discussed.

Abstract The workbench is an interesting semi‐immersive configuration for interactive tasks. However, haptic feedback, i.e.force and tactile feedback, is one important cue which is missing. To the authors' knowledge, the sole proposedsolution consists in installing an arm force feedback device on one‐screen workbenches. This solution, however,has several drawbacks. The arm can perturb the stereoscopic display, cross virtual objects or hide parts of thevisualization space. Furthermore, the interaction space is limited by the size of the arm, which may also damagethe screen or perturb the electromagnetic tracking system. Some of these difficulties may even be worth with a two‐screenworkbench. This paper discusses an alternative solution, which consists in integrating a stringed hapticdevice on a workbench. This approach is less invasive, more flexible and well‐suited to a two‐screen workbench.

This paper presents a new virtual locomotion interface based on step-in-place action and a smart-turntable system. The interface provides a turntable as walking platform, on top of which users will stand at its center, and facing a large screen, to perform life-like walking actions that steer their navigation through the virtual environment. Steering actions are tracked seamlessly without attachment to the body through a set of pressure sensors embedded within the turntable and a computer vision system. For instance, in place stepping is treated as a gesture indicating the intention to move forward. Rotation about the body's vertical axis is treated as a gesture changing the walking direction. However, as large screens are usually limited in size and do not allow a surrounding projection, a large turning action may put users in a visual-less situation, which hamper considerably the effectiveness of the walking experience. To avoid such case and keep users always provided with sufficient visual feedback, the turntable will passively and smoothly rotate in opposite direction of users' turning. Rotation speed and acceleration of the turntable are well optimized to keep users well balanced and easily withstand the passive rotation. The interface is shown to be easy and simple to use in virtual environments equipped with large screen.

Omni-directional locomotion systems are yet of little advantage in virtual environments (VEs) with limited large display systems, where users may experience visual-less situations when they move in a direction that is not covered by the large screen. This paper presents a new omni-directional locomotion interface based on step-in-place movement and a smart-turntable system to impart users with the ability to move freely in any direction within VEs without loosing sight of the displayed image despite its projection on a limited large screen that does not provide surrounding or 360/spl deg/ visual feedback. The novelty of the interface is that: (a) it uses a smart-turntable with embedded sensors as a walking platform that compensate users' rotations rather than their displacements; (b) no cable attachments are made to the user body; and (c) the user can make many full body rotations without loosing sight of the environment, virtually providing a surrounding display despite the use of the limited size screen.

We demonstrate a new intuitive force feedback device for advanced VR applications. Force feedback for the device is tension based and is characterized by 7 degrees of freedom (DOF); 3 DOF for translation, 3 DOF for rotation, and 1 DOF for grasp. The SPIDAR-G (Space Interface Device for Artificial Reality with Grip) will allow users to interact with virtual objects naturally by manipulating two hemispherical grips located in the center of the device frame. We show how to connect the strings between each vertex of grip and each extremity of the frame in order to achieve force feedback. In addition, methodologies will be discussed for calculating translation, orientation and grasp using the length of 8 strings connected to the motors and encoders on the frame. The SPIDAR-G exhibits smooth force feedback, minimized inertia, no backlash, scalability and safety. Such features are attributed to strategic string arrangement and control that results in stable haptic rendering. The design and control of the SPIDAR-G is described in detail and the space graphic user interface system based on the proposed SPIDAR-G system is demonstrated. Experimental results validate the feasibility of the proposed device and reveal its application to virtual reality.

This paper describes the principle and experimental results of a camera system that is composed of a commercially available CCD camera, a large-aperture lens, and an intermediate screen used to measure the distance between the camera and a far-away object by using depth from focus method.

The paper aims to present a new human-scale haptic device for virtual environment named Scaleable-SPIDAR (Space Interface Device for Artificial Reality), which provide to both hands different aspects of force feedback sensations, associated mainly with weight, contact and inertia within a cave-like space. Tensioned string techniques are used to generate such haptic sensations, while keeping the space transparent and unbulky. The device is scaleable so as to enclose different cave-like working space. Scaleable-SPIDAR is coupled with a large screen where a computer generated virtual world is displayed. The used approach is shown to be simple, safe and multi-modal interface for human-scale virtual environment (VE).

We propose a 3-D video display technique that allows multiple viewers to observe 3-D images from a 360-degree horizontal arc without wearing 3-D glasses. This technique uses a cylindrical parallax barrier and a one-dimensional light source array. We have developed an experimental display using this technique and have demonstrated observation of 3-D images from a 360-degree horizontal arc without the use of 3-D glasses. Since this technique is based on the parallax panoramagram, the parallax number and resolution are limited by the diffraction at the parallax barrier. To overcome these limits, we improved the technique by revolving the parallax barrier. We have incorporated this new technique in our new experimental display. The display is capable of displaying cylindrical 3-D video images within a diameter of 100 mm and a height of 128 mm. Images are described with a resolution of 1254 pixels circularly and 128 pixels vertically and are refreshed at 30 Hz. Each pixel has a viewing angle of 60 degrees that is divided into 70 views, so the angular parallax interval of each pixel is less than 1 degree. In such a case, observers may barely perceive discrete parallax. The pixels are arranged on a cylindrical surface to allow the produced 3-D images to be observed from all directions.

We propose a novel two-handed multi-finger haptic interface device. This system is another kind of string based hand haptic display system. DC motors, rotary encoders, pulleys, and strings are used to measure the position of eight fingertips of the user in real time. When any fingertip comes into contact with any virtual object, the system will control the tension of the strings pulled by the motors to display force feedback at that fingertip of the user. We briefly describe the system as well as the methods used for calculation of the fingertip positions and the generation of force feedback.

Continuous advances in computer technology are making it possible to construct virtual environments with an ever-increasing sense of visual realism. What is lacking are interfaces that allow users to manipulate virtual objects in an intuitive manner. In this paper, we present a 7 DOF tension-based haptic interface that allows users to not only grip an object but also to sense an object's width. We have developed a system to utilize the physical action of gripping to display grasp manipulation in virtual environments. We also present a method to calculate the position and display force associated with this gripping mechanism. Finally, we show the validity of our proposed haptic interface through examples.

This paper proposes a method of multiscale image analysis through an operator called the "surface-shape operator". By considering an image function as a surface function, the surface-shape operator describes shape of each pixel in terms of the topographic structure such as hill, dale, ridge, valley, etc. The surface-shape operator is used as a pre-processing for extracting the multiscale topographic structures of images in scale-space representation. Then, image features are extracted from the transformed images instead of the original ones. The surface-shape operator has invariant properties under monotonic and linear gray tone transformations, and is insensitive to additive noise modelled by linear functions, so the proposed method has a robustness with brightness variations and shading effects. We illustrate the usefulness of the proposed method with an application to image classification, and also demonstrate performances concerning the robustness with brightness variations and shading effects. The multiresolution simultaneous autoregressive (MRSAR) method is selected as a representative method of multiscale approaches for image classification used to-date for comparison purposes. Results show that the proposed method performs better and has much more robustness with brightness variations and shading effects than the MRSAR method.

This paper introduces new features for describing image patterns. We integrate the concepts of multiscale image analysis, aura matrix to define image features, and to obtain the features having robustness with illumination variations and shading effects, we analyse images based on the topographic structure described by the surface-shape operator. Then, illustrate usefulness of the proposed features with texture classifications. Results show that the proposed features extracted from multiscale images work much better than those from a single scale image, and confirm that the proposed features have robustness with illumination and shading variations. By comparisons with the multiresolution simultaneous autoregressive features using Mahalanobis distance and Euclidean distance, the proposed multiscale features give better performances for classifying the entire Brodatz textures (1966).

Two kinds of program partitioning optimizations are proposed. The first extends program partitioning using array subscript functions to deal with two cases about array elements on the left hand side of assignment statements in the loop: (a) the same loop control variables exist in different dimensions, (b) plural loop control variables exist in one dimension. The second removes statement guards generated in a loop by program partitioning in two cases about loop iteration ranges of statements in the loop: (c) ranges of plural statements for one processor are potentially different, (d) ranges of one statement for plural processors are potentially different. The first is proved to be efficient for the BEM program. The second is implemented in a simplified way in our HPF prototype compiler, and compiler output to Shallow Water program has as good performance as a hand optimized one.

In this paper, we propose a new operator called shape operator for describing image structure. We consider an image function as a surface, then describe a shape of each pixel comparing with its neighbourhood in terms of topographical shapes such as hill, dale, ridge, valley, etc. The shape operator is established by utilizing the eigenvalues of Hessian of an image function. We show how to derive this operator, and its interesting properties. Finally, we illustrate by examples how the shape operator can give the same interpretation of an image although the image is corrupted by shading effects, and how it can give the same interpretation of an image viewed in different viewpoints.

Deals with a hierarchical description of digital grayscale images based on non-local structural features, called image dipoles. An image dipole is defined to be a region whose lines of slope emanate from the same maximum, and reach the same minimum. Incorporating an image dipole based representation of an image into a scale-space filtering, we propose in this paper a hierarchical image dipole description of the image. The proposed description consists of image dipole networks of some scales, and linking of image dipoles across the scales such that the description contains all local transformations of the image dipole network in the scale-space.

A new segmentation method called Gaussian segmentation, which can "discover" objects successively in any situation, is presented. The method extracts regions containing locally concentrated stimuli. Similarly, the visual system of humans uses this function to extract the objects from images if no prior information about the objects is available. As a mathematical model, assigning regions as the Gaussian distribution, the extraction of regions in the Gaussian segmentation can be formalized as an optimization problem. The result given by the method coincides with the fact that the extraction, of regions of interest depends naturally on the scale of observation or the visual field.

To develop a computer vision system, it is necessary to define a proper image structure representation to be used for interpreting images efficiently. In this paper, we propose a new operator called shape operator for describing topographical image structure. We consider an image function as a surface, then describe a shape of each pixel comparing with its neighbourhood in terms of topographical shapes such as hill, dale, ridge, valley, etc. The shape operator is established by utilizing the eigenvalue of Hessian of an image function. It is expressed in an explicit form in terms of the second order partial derivatives of an image function. We show how to derive this operator, its interesting properties, and an application for texture classification. Experimental results show its good performance for discriminating texture imaged. Especially, it can give the same interpretation of an image reflected in different lighting conditions since it has the invariance properties under linear and monotonic gray tone transformations.

A feature called "stroke index" is introduced for document image analysis. It is based on the minimum covering run (MCR) expression method is introduced. This stroke index is a function of the number of horizontal and vertical runs in the original image and of number of runs by the MCR expression. As document images may present a variety of patterns such as graph, text, picture, or dithered image, it is necessary for image understanding to classify these different patterns into categories beforehand. It is shown how one could use this stroke index for such applications as classification or segmentation. This paper also gives an insight into the possibility of stroke extraction from document images, in addition to classifying different patterns in a compound image.>

Proposes a new method for expressing binary images, named minimum covering run (MCR) expression. The proposed technique adapted from horizontal-vertical run expression, is derived by selecting suitable runs from horizontal and vertical run types which minimize the total number of runs that still represent the original images perfectly. It is shown that horizontal and vertical runs of binary image can be thought as partite sets of a bipartite graph. Consequently, the MCR expression that corresponds to maximum matching in the graph, can be found by using an algorithm solving this graph-theoretic problem. An efficient algorithm for the expression method is presented, and results show the validity of stroke extraction of information in document images.>

For pattern information processing like recognition or understanding, one must express the given pattern properly for later processing. Many ways have been developed to express the hierarchy of a pattern, but many of them use one dimensional or two dimensional patterns. It is important to find an expression reflecting the hierarchical structure of a spherical pattern. In this paper, the authors propose the scale space filtering on a spherical pattern to express its hierarchy.>

To develop a human interface for three- dimensional modeling it is necessary to construct a vir- tual work space where we can manipulate object models directly, just as in real space. In this paper, we propose a new interface device SPIDAR (Space Interface Device for Artificial Reality) for this virtual work space. SPIDAR can measure the position of a finger and give force feed- back to a finger when it touches the virtual object. We

Scale-space filtering is a multiresolutional filtering method which expands a waveform to the set of waveforms in multiscale measurement. The intervals bounded by zero-crossings of expanded waveforms have a hierarchical structure, which can be represented by an interval tree. Another hierarchical description of the waveform, scale-space tree, is introduced as a natural description of the hierarchy. The difference hierarchy between the interval tree and the scale-space tree is discussed.>

Some examples of the structure line are shown and the morphological transition of the structure line is investigated. The waveform that causes the catastrophe of tree structure plays an important role in the transition. This waveform is called a catastrophe waveform. The catastrophe waveform means the transformation of the tree structure. Since the transformations of the branch such as separation and connection do not occur at the same time, an isolated tree must appear between these transformations.>

Scale-space filtering is a multiresolution filtering, which is defined as the convolution of a random waveform f(x) with the Gaussian kernel w(x,σ). The set of filtered waveform f(x,σ), called generalized waveform of f(x), is very useful for the structural analysis of waveforms. In this paper, we introduce an analytic line, named structure line, on the surface of generalized waveform f(x,σ). Structure line describes the relation of the convex and concave region of generalized waveform. Structure line is defined by some derivatives of generalized waveform, and has the same topological structure as a trinary tree. The properties of structure line are discussed and some examples are shown. It is confirmed that the structure line is effective to represent waveforms hierarchically.