Insung Ihm

Wavelet-Based 3D Compression Scheme for Interactive Visualization of Very Large Volume Data

Interactive visualization of very large volume data has been recognized as a task requiring great effort in a variety of science and engineering fields. In particular, such data usually places considerable demands on run‐time memory space. In this paper, we present an effective 3D compression scheme for interactive visualization of very large volume data, that exploits the power of wavelet theory. In designing our method, we have compromised between two important factors: high compression ratio and fast run‐time random access ability. Our experimental results on the Visual Human data sets show that our method achieves fairly good compression ratios. In addition, it minimizes the overhead caused during run‐time reconstruction of voxel values. This 3D compression scheme will be useful in developing many interactive visualization systems for huge volume data, especially when they are based on personal computers or workstations with limited memory.

Algebraic surface design with Hermite interpolation

This paper presents an efficient algorithm called Hermite interpolation, for constructing low-degree algebraic surfaces, which contain, with C1 or tangent plane continuity, any given collection of points and algebraic space curves having derivative information. Positional as well as derivative constraints on an implicitly defined algebraic surface are translated into a homogeneous linear system, where the unknowns are the coefficients of the polynomial defining the algebraic surface. Computaional details of the Hermite interpolation algorithm are presented along with several illustrative applications of the interpolation technique to construction of joining or blending surfaces for solid models as well as fleshing surfaces for curved wire frame models. A heuristic approach to interactive shape control of implicit algebraic surfaces is also given, and open problems in algebraic surface design are discussed.

3D RGB image compression for interactive applications

This paper presents a new 3D RGB image compression scheme designed for interactive real-time applications. In designing our compression method, we have compromised between two important goals: high compression ratio and fast random access ability, and have tried to minimize the overhead caused during run-time reconstruction. Our compression technique is suitable for applications wherein data are accessed in a somewhat unpredictable fashion, and real-time performance of decompression is necessary. The experimental results on three different kinds of 3D images from medical imaging, image-based rendering, and solid texture mapping suggest that the compression method can be used effectively in developing real-time applications that must handle large volume data, made of color samples taken in three- or higher-dimensional space.

Higher-order interpolation and least-squares approximation using implicit algebraic surfaces

In this article, we characterize the solution space of low-degree, implicitly defined, algebraic surfaces which interpolate and/or least-squares approximate a collection of scattered point and curve data in three-dimensional space. The problem of higher-order interpolation and least-squares approximation with algebraic surfaces under a proper normalization reduces to a quadratic minimization problem with elegant and easily expressible solutions. We have implemented our algebraic surface-fitting algorithms, and included them in the distributed and collaborative geometric environment SHASTRA. Several examples are given to illustrate how our algorithms are applied to algebraic surface design.

Practical animation of turbulent splashing water

Despite recent advances in fluid animation, producing small-scale detail of turbulent water still remains challenging. In this paper, we extend the well-accepted particle level set method in an attempt to integrate the dynamic behavior of splashing water easily into a fluid animation system. Massless marker particles that still escape from the main body of water, in spite of the level set correction, are transformed into water particles to represent subcell-level features that are hard to capture with a limited grid resolution. These physical particles are then moved in the air through a particle simulation system that, combined with the level set, creates realistic turbulent splashing. In the rendering stage, the particles physical properties such as mass and velocity are exploited to generate a natural appearance of water droplets and spray. In order to visualize the hybrid water, represented in both level set and water particles, we also extend a Monte Carlo ray tracer so that the particle agglomerates are smoothed, thickened, if necessary, and rendered efficiently. The effectiveness of the presented technique is demonstrated with several examples of pictures and animations.

Smoothing polyhedra using implicit algebraic splines

Polyhedron “smoothing” is an efficient construction scheme for generating complex boundary models of solid physical objects. This paper presents efficient algorithms for generating families of curved solid objects with boundaty topology related to an input polyhedron. Individual faces of a polyhedron are replaced by low degree implicit algebraic surface patches with local support. These quintic patches replace the @ contacts of planar facets with C’ continuity along all irtterpatch boundaries. Selection of suitable instances of implicit surfaces as well as local control of the individual surface patches are achieved via simultaneouss interpolation and weighted least-squares approximation.

Mobile collaborative medical display system

Because of recent advances in wireless communication technologies, the world of mobile computing is flourishing with a variety of applications. In this study, we present an integrated architecture for a personal digital assistant (PDA)-based mobile medical display system that supports collaborative work between remote users. We aim to develop a system that enables users in different regions to share a working environment for collaborative visualization with the potential for exploring huge medical datasets. Our system consists of three major components: mobile client, gateway, and parallel rendering server. The mobile client serves as a front end and enables users to choose the visualization and control parameters interactively and cooperatively. The gateway handles requests and responses between mobile clients and the rendering server for efficient communication. Through the gateway, it is possible to share working environments between users, allowing them to work together in computer supported cooperative work (CSCW) mode. Finally, the parallel rendering server is responsible for performing heavy visualization tasks. Our experience indicates that some features currently available to our mobile clients for collaborative scientific visualization are limited due to the poor performance of mobile devices and the low bandwidth of wireless connections. However, as mobile devices and wireless network systems are experiencing considerable elevation in their capabilities, we believe that our methodology will be utilized effectively in building quite responsive, useful mobile collaborative medical systems in the very near future.

Animation of reactive gaseous fluids through chemical kinetics

Although chemically reactive fluids may be used effectively to increase the reality of visual effects, little work has been done with the general modeling of chemical reactions in computer animation. In this paper, we attempt to extend an established, physically based fluid simulation technique to handle reactive gaseous fluids. The proposed technique exploits the theory of chemical kinetics to account for a variety of chemical reactions that are frequently found in everyday life. In extending the existing fluid simulation method, we introduce a new set of physically motivated control parameters that allow an animator to control intuitively the behavior of reactive fluids. Our method is straightforward to implement, and is flexible enough to create various interesting visual effects including explosions and catalysis. We demonstrate the effectiveness of our new simulation technique by generating several animation examples with user control.

Piecewise linear approximations of digitized space curves with applications

Generating piecewise linear approximations of digitized or “densely sampled” curves is an important problem in many areas. Here, we consider how to approximate an arbitrary digitized 3-D space curve, made of n+1 points, with m line segments. We present an O(n 3 log m) time, O(n 2 log m) space, dynamic programming algorithm which finds an optimal approximation. We then introduce an iterative heuristic algorithm, based upon the notions of curve length and spherical image, which quickly computes a good approximation of a space curve in O(N iter n) time and O(n) space. We apply this fast heuristic algorithm to display space curve segments and implicit surface patches, and to linearly approximate curved 3D objects, made by rotational sweeping, by binary space partitioning trees that are well-balanced.

Strong matching preclusion

The matching preclusion problem, introduced by Brigham et al. R.C. Brigham, F. Harary, E.C. Violin, and J. Yellen, Perfect-matching preclusion, Congressus Numerantium 174 (2005) 185?192, studies how to effectively make a graph have neither perfect matchings nor almost perfect matchings by deleting as small a number of edges as possible. Extending this concept, we consider a more general matching preclusion problem, called the strong matching preclusion, in which deletion of vertices is additionally permitted. We establish the strong matching preclusion number and all possible minimum strong matching preclusion sets for various classes of graphs.