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Koichi Hirota
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Journal Articles
Publisher: Journals Gateway
Presence: Teleoperators and Virtual Environments (2004) 13 (3): 355–370.
Published: 01 June 2004
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In this paper, we propose an approach to real-time haptic interaction based on the concept of simulating the constraining propertes of space. Research on haptic interaction has been conducted from the points of view of both surface and volume rendering. Most approaches to surface rendering—such as the constraint-based god-object method, the point-based approach, and the virtual proxy approach—have dealt only with the interaction with an object surface. Whereas, in volume rendering approaches, algorithms for representing volume data through interactions in space have been investigated. Our approach provides a framework for the representation of haptic interaction with both surface and space. We discretize the space using a tetrahedral cell mesh and associate a constraining property with each cell. The interaction of the haptic interface points with a volume is simulated using the constraining properties of the cells occupied by this volume. We implemented a fast computation algorithm that works at a haptic rate. The algorithm is robust in that any sudden or quick motion of the user does not disturb the computation, and the computation time for each cycle is independent of the complexity of the model as a whole. To demonstrate the performance of the proposed method, we present experimental results on the interaction with models of varying complexity. Also, we discuss some problems that need to be solved in future work.
Journal Articles
Publisher: Journals Gateway
Presence: Teleoperators and Virtual Environments (2003) 12 (1): 96–109.
Published: 01 February 2003
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In this paper, we discuss possible applications of virtual reality technologies, such as immersive projection technology (IPT), in the field of genome science, and propose cluster-oriented visualization that attaches importance to data separation of large gene data sets with multiple variables. Based on these strategies, we developed the cluster overlap distribution map (CDCM), which is a visualization methodology using IPT for pairwise comparison between cluster sets generated from different gene expression data sets. This methodology effectively provides the user with indications of gene clusters that are worth a close examination. In addition, by using the plate window manager system, which enables the user to manipulate existing 2D GUI applications in the virtual 3D space, we developed the virtual environment for the comprehensive analysis from providing the indications to further examination by referring to the database on Web sites. Our system was applied in the comparison between the gene expression data sets of hepatocellular carcinomas and hepatoblastomas, and the effectiveness of the system was confirmed.
Journal Articles
Publisher: Journals Gateway
Presence: Teleoperators and Virtual Environments (2001) 10 (5): 525–536.
Published: 01 October 2001
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In this paper, a method for visually and haptically representing elastic objects in a virtual environment is proposed. A linear FEM (finite-element method) model is employed to define the elasticity of an object. By computing the inverse stiffness matrix in advance, the force and the displacement according to the interaction are obtained in real time using the precomputed inverse stiffness matrix. Based on the fast-computation method of FEM, an approach for implementing an elastic virtual object is proposed. In this approach, a force interpolation method is introduced to realize a smooth change of the feedback force on the surface of objects. Moreover, the force update process and deformation process are executed asynchronously to attain a high update rate of force.
Journal Articles
Publisher: Journals Gateway
Presence: Teleoperators and Virtual Environments (1998) 7 (6): 638–649.
Published: 01 December 1998
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The sensations of touch and force have come to be recognized as essential factors in virtual reality, and many efforts have been made to develop display devices that reproduce these sensations. Such devices are divided into two categories: wearing and nonwearing. In this paper, a method is proposed for representing virtual objects of arbitrary shapes using a nonwearing device. Based on this method, a device was fabricated to describe our approach. Our prototype device was designed to approximately represent part of the surface of a virtual object as a tangential surface (i.e., partial surface) to the user's fingertip. The device was implemented as a mechanism with five degrees of freedom that are commonly used to measure the fingertip position and to present the partial surface to the fingertip. The mechanism was controlled through two calculation loops: a model loop that gives a tangential surface from the fingertip position and the shape of objects, and a servo loop that manages the mechanism to represent the given tangential surface by the partial surface. Also, a stereoscopic, head-tracking visual system was implemented to realize the combined presentation of visual information and the partial surface. As an example of the applications of the environment, a task of writing characters was simulated. From the observation of the performance of the task, the presentation of the partial surface was proved to have an effect on decreasing blur and dragging in written characters.