8. Simulation Science Basis Group

We research three-dimensional scientific visualization technology to visualize the simulation and experiment results, and to contribute to the device design by the virtual-reality system. We investigate the technology in order to use the computer and its environment more highly, which are indispensable to perform simulation researches.

Introduction of research 1 Analysis of simulation data by virtual-reality system

Introduction of research 2 Integrated scientific visualization of simulation and experimental device data by virtual-reality system

Introduction of research 3 Irreversible data compression concepts in time-order of particle trajectory for visualization of huge particle system

Introduction of simulation code

Introduction of research 1

Analysis of simulation data by virtual-reality system 1
Computer produces huge numerical data in the calculation process of simulation research. It is difficult to know what happens in the simulation even when you watch such the raw data. It becomes able to understand first the state of the simulation when you adapt the data to an easy-to-understand expression, such as, a graph and a contour plot of the numerical data.

Recently, a large-scale three-dimensional simulation has been performed because of rapidly-advancing technology of super-computer. These data are usually shown and analyzed on the two-dimensional plane through the monitor by three-dimensional visualization software. However, since the depth information is not sufficient, it is difficult or impossible to understand the spatial structure of physical quantities, which are calculated in three-dimensional space (ex. magnetic field structure, and the particle orbits). For this reason, it is desirable to analyze the three-dimensional simulation results in the three-dimensional space.

In this research, we performed an analysis by an immersive virtual-reality system gCompleXcopeh in order to understand the three-dimensional simulation results in three-dimensional space. CompleXcope is composed of room-size four screens for stereo and immersive view, liquid-crystal glasses with tracking system for stereo and interactive view, and three-dimensional mouse Wand for interactive view. Viewer with liquid-crystal glasses comes into the room surrounded by the four screens. It is possible to see the stereo and immersive view through the liquid-crystal glasses. When the viewer moves its head or walks in the room, the images on the screens are reconstructed rapidly according to its movement by tracking system. The viewer feels itself being in the simulation model with high immersive feeling, and it can watch the three-dimensional objects with any size and from all directions.

By means of CompleXcope, we investigated the particle behavior in the electromagnetic field obtained by simulation. As a result, it was clearly shown that the particle motion which drew a complex three-dimensional orbit played an important role in the magnetic reconnection phenomena. The visualization software (VFIVE and its expansion version) can serve functions, which are expected to be applied to other fields as well as the reconnection research. It is worthy of attention as an important guiding principle for an establishment of basic technology of simulation science and a progress of simulation research.


ReferenceFgScientific Visualization of Magnetic Reconnection Simulation Data by CAVE Virtual Reality Systemh, H. Ohtani and R. Horiuchi, Plasma and Fusion Research, 3, (2008), 054.

Immersive virtual-reality systemgCompleXcopeh.

Scientific visualization of magnetic reconnection simulation by VFIVE expansion version.

Introduction of research 2
Integrated scientific visualization of simulation and experimental device data by virtual-reality system

We integrally visualize simulation results of equilibrium plasma in the vacuum vessel of Large Helical Device (LHD) by CompleXcope. Since the experimental device, data is based on CAD software, the devices such as diverter plates and cyclotron heating antennae are located in the same positions as those in the actual LHD vessel. Under the results of magnetohydrodynamics (MHD) equilibrium simulation code "HINT," An isosurface of a plasma pressure, a magnetic field line and an orbit of drift particle can be calculated and displayed in VR space interactively. From this success, a lot of attractive potentialities have opened up for intuitively understanding the physics of plasma, for aiding in the design and arrangement of the devices, and for confirming the field of vision from the observation port in VR space.

Integrated virtual-reality visualization of simulation and experimental device.

gScientific Visualization of Plasma Simulation Results and Device Data in Virtual-Reality Spaceh, H.Ohtani, Y.Tamura, A.Kageyama, S.Ishiguro, IEEE Transactions on Plasma Science Special Issue - Images in Plasma Science 2011, 39 (11), (2011), 2472-2473. DOI:10.1109/TPS.2011.2157174

gIntegrated Visualization of Simulation Results and Experimental Devices in Virtual-Reality SpacegCH.Ohtani, A.Kageyama, Y.Tamura, S.Ishiguro, M.Shohji, Plasma and Fusion Research, 6, (2011), 2406027 (4pages). DOI: 10.1585/pfr.6.2406027

EH.Miyachi et al: IEEE Computer Society, (2005), 530.

EH.Miyachi et al: IEEE Computer Society, (2007), 536. 

Introduction of research 3
Irreversible data compression concepts in time-order of particle trajectory for visualization of huge particle system
We proposed a data compression scheme for large-scale particle simulations, which had favorable prospects for scientific visualization of particle systems. Our data compression concepts dealt with the data of particle orbits obtained by simulation directly. We named this concept gTOKI (Time-Order Kinetic Irreversible compression)h. We presented an example of an implementation of the data-compression scheme and showed several application results and good data compression rates under the error control for plasma and galaxy formation simulation data.

Reproducibility of the compressed data. Time evolution of the particle x coordinate of three-dimensional plasma particle simulation is shown. Red line indicates the decoded data, and green plus symbol shows the simulation data.

  • Reference:
    (1) H.Ohtani, K.Hagita, A.M.Ito, T.Kato, T.Saitoh and T.Takeda: Journal of Physics: Conference Series, accepted (2013).

Introduction of simulation code

  • Subject: To analyze interactively and three-dimensionally the three-dimensional field data, such as the flow and magnetic fields, with a deep absorption into the data space.
  • Function: Input data are the multiple scalar and vector fields defined on the Cartesian coordinate. It serves basic visualization functions, such as isosurface, cross section, volume rendering, streamline, arrow expression of vector field. It also serves original functions, which bring out the best in the virtual-reality interactive environment.
  • Features: It is possible to analysis the data interactively reflecting the characteristics of the virtual-reality, for example, release of tracing particles from the three-dimensional mouse one after another, observation of movement of several hundred tracing particles, which seem like dancing, blown by the wind, in the virtual spot light radiated from the mouse.
  • Reference:
    (1) Nobuaki Ohno, and Akira Kageyama, Region-of-Interest Visualization by CAVE VR System with Automatic Control of Level-of-Detail, Comput. Phys. Comm., vol.181, pp.720-725 (2010)
    (2)A. Kageyama, and N. Ohno, Interactive Three-Dimensional Visualization Software by Virtual Reality Technology, Journal of Plasma and Fusion Research, vol.84, No.11, pp.834--843 (2008)
    (3) N. Ohno and A. Kageyama, Scientific Visualization of Geophysical Simulation Data by the CAVE VR System with Volume Rendering, Phys. Earth Planet. Interiors, vol.163, pp.305--311, doi:10.1016/j.pepi.2007.02.013 (2007)
    (4) N. Ohno, A. Kageyama, and K. Kusano, Virtual Reality Visualization by CAVE with VFIVE and VTK, J. Plasma Physics., J. Plasma Physics, vol.72, part 6, pp.1069-1072 (2006)
    (5) Akira Kageyama, Yuichi Tamura, and Tetsuya Sato, Visualization of Vector Field by Virtual Reality, Progress of Theoretical Physics Supplment, Vol. 138, (2000), pp.665-673
    (6) Akira Kageyama, Yuichi Tamura, and Tetsuya Sato, Scientific Visualization in Physics Research by CompleXcope CAVE System, Transactions of the Virtual Reality Society of Japan, Vol.4, No.4 (1999) pp.717-722