2011 Fiscal Year

Domestic Academic Journals (in Japanese)

Masato Odagawa,Yuriko Takeshima,Issei Fujishiro,Gota Kikugawa,Taku Ohara
GPU-Based Adaptive Visualization for Particle Systems
in Transactions of the Japan Society of Mechanical Engineers (Series B),Vol. 77, No. 781, pp. 1767-1778,September 2011
When visualizing large-scale particle systems, it is difficult to maintain adequate framerates because we have to render dynamic scenes with a large number of small spheres. For the control of trade-offs between the overall image quality and total rendering speed, we propose a new rendering scheme which uses a fast method based on shaded texture mapping and a high-quality implicit surface method in a combined way. The shaded texture mapping, which generates a pseudo-texture through alpha-blending a proper portion of template texture for shade and highlight onto a base spherical texture, can render a particle faster than the implicit surface method. However, a weakness of the texture mapping lies in its poor shading quality. In contrast, the implicit surface method is accurate enough for analyzing particle systems visually. Actual method to render each particle is decided according to the viewing distance; the high-quality method is chosen only when the distance is smaller than a threshold, to allow the user to observe the region of interest closely. We use a molecular dynamics simulation dataset to evaluate the effectiveness of our scheme empirically. In addition to this, we also consider the extensibility of our scheme in terms of framerate stability, scalability, and expressiveness.

International Conference Proceedings

Satoshi Mabuchi, Yoshio Ohno, Issei Fujishiro
SPH-based method for interactive flame simulation – Implementation on CPU and GPU
in Proceedings of ASIAGRAPH2011, pp. 41-46, Tokyo (Japan), October 2011
DL, 学会ページ
In this paper, we propose a novel, particle-based flame simulation method, which relies on SPH to simulate the dynamics of flames by introducing a buoyancy term as an external force to the Navier-Stokes equations. The buoyancy term is directly affected by heat generated from a simple chemical reaction model. For efficiency, we adaptively re-sample particles around a flame. We demonstrate that it is possible to execute three-dimensional flame simulations in real-time for typical cases including transition from initial to stable states, and one-way coupling with solid. Our method offers reasonable results on CPU, while more realistic results can be obtained using GPGPU.

Shigeo Takahashi, Issei Fujishiro, Yuriko Takeshima, Kenichi Yoshida
Previewing volume decomposition through optimal viewpoints
in Scientific Visualization: Interactions, Features,Metaphors, (Hans Hagen, ed.), electronic volume in the series Dagstuhl Follow-Ups (ISSN 1868–8977), 2011
DL, 学会ページ
Understanding a volume dataset through a 2D display is a complex task because it usually contains multi-layered inner structures that inevitably cause undesirable overlaps when projected onto the display. This requires us to identify feature subvolumes embedded in the given volume and then visualize them on the display so that we can clarify their relative positions. This article therefore introduces a new feature-driven approach to previewing volumes that respects both the 3D nested structures of the feature subvolumes and their 2D arrangement in the projection by minimizing their occlusions. The associated process begins with tracking the topological transitions of isosurfaces with respect to the scalar field, in order to decompose the given volume dataset into feature components called interval volumes while extracting their nested structures. The volume dataset is then projected from the optimal viewpoint that archives the best balanced visibility of the decomposed components. The position of the optimal viewpoint is updated each time when we peel off an outer component with our interface by calculating the sum of the viewpoint optimality values for the remaining components. Several previewing examples are demonstrated to illustrate that the present approach can offer an effective means of traversing volumetric inner structures both in an interactive and automatic fashion with the interface.

Yuriko Takeshima, Issei Fujishiro, Shigeo Takahashi, Toshiyuki Hayase
Measurement-integrated simulation and visualization of Karman vortex streets in Hybrid Wind Tunnel
in Proceedings of ASIAGRAPH2011, pp. 35-40, Tokyo (Japan), October 2011
DL, 学会ページ
We have developed a hybrid wind tunnel, where 2D measurement-integrated (MI) simulation, which utilizes actual data acquired from real air flow behind a square cylinder, plays an important role in improving the accuracy of its numerical analysis. The wind tunnel requires an accompanying visual analysis tool with which we can effectively peer into the relationships between the actual and simulated flow fields. In this paper, we attempt to exploit the augmented reality-style display technique to that end. The basic idea is to instantaneously superimpose the computationally-visualized MI simulated pressure field onto the actual flow velocity structure physically-visualized with oil mist-traced streak lines. Space registration of these two visual sources is rather straight-forward since the fixed cylinder of the wind tunnel is easily identified, whereas visualizing the MI simulated pressure field can be characterized with its sophisticated scheme based on differential topology. Considering the facts that vortex centers are located at local minima in the pressure field, and each minimum is surrounded by a derived topological feature called ravine cycle, we can colorize the field adaptively and keep track of Karman vortex streets robustly, regardless of drastic change in the Reynolds number of the flow field.

Hidei Kimura, Akira Asano, Issei Fujishiro, Ayaka Nakatani, Hayato Watanabe
True 3D display
presented at ACM SIGGRAPH 2011 Emerging Technologies, Article No. 20, Vancouver, August 7, 2011
Realizing a true three-dimensional (3D) display environment has been an ultimate goal of visual computing communities. Burton Inc. in Japan and others built upon the modern laser-plasma technology to come up with 3D Aerial Display device in 2006, with which the users are allowed to plot a unicursal series of illuminants freely in the midair, and thus the surrounding audience can enjoy watching different aspects of the 3D image from different positions, without any eye strain [Kimura et al. 2006].

Kazuhide Ueda, Issei Fujishiro
Visual simulation of bleeding on skin surface
in Proceedings of ACM SIGGRAPH 2011 Posters, Article No. 9, Vancouver, August 9, 2011
The liquid behavior has a significant impact on video works, and bleeding is no exception. Hemorrhage scenes possess highly important implications, as seen from the fact that they might make the work rated age limit. Lack of visual reality in the involved scenes would reduce the overall quality of the work.

Chongke Bi, Shigeo Takahashi, Issei Fujishiro
Degeneracy-aware interpolation of 3D diffusion tensor fields
in Proceedings of SPIE VDA 2012, No. 8294–829411, SanFrancisco, January 2012
Visual analysis of 3D diffusion tensor fields has become an important topic especially in medical imaging for understanding microscopic structures and physical properties of biological tissues. However, it is still difficult to continuously track the underlying features from discrete tensor samples, due to the absence of appropriate interpolation schemes in the sense that we are able to handle possible degeneracy while fully respecting the smooth transition of tensor anisotropic features. This is because the degeneracy may cause rotational inconsistency of tensor anisotropy. This paper presents such an approach to interpolating 3D diffusion tensor fields. The primary idea behind our approach is to resolve the possible degeneracy through optimizing the rotational transformation between a pair of neighboring tensors by analyzing their associated eigenstructure, while the degeneracy can be identified by applying a minimum spanning tree-based clustering algorithm to the original tensor samples. Comparisons with existing interpolation schemes will be provided to demonstrate the advantages of our scheme, together with several results of tracking white matter fiber bundles in a human brain.