Ching-Kuang Shene

Hierarchical Streamline Bundles

Effective 3D streamline placement and visualization play an essential role in many science and engineering disciplines. The main challenge for effective streamline visualization lies in seed placement, i.e., where to drop seeds and how many seeds should be placed. Seeding too many or too few streamlines may not reveal flow features and patterns either because it easily leads to visual clutter in rendering or it conveys little information about the flow field. Not only does the number of streamlines placed matter, their spatial relationships also play a key role in understanding the flow field. Therefore, effective flow visualization requires the streamlines to be placed in the right place and in the right amount. This paper introduces hierarchical streamline bundles, a novel approach to simplifying and visualizing 3D flow fields defined on regular grids. By placing seeds and generating streamlines according to flow saliency, we produce a set of streamlines that captures important flow features near critical points without enforcing the dense seeding condition. We group spatially neighboring and geometrically similar streamlines to construct a hierarchy from which we extract streamline bundles at different levels of detail. Streamline bundles highlight multiscale flow features and patterns through clustered yet not cluttered display. This selective visualization strategy effectively reduces visual clutter while accentuating visual foci, and therefore is able to convey the desired insight into the flow data.

ThreadMentor: a pedagogical tool for multithreaded programming

ThreadMentor is a multiplatform pedagogical tool designed to ease the difficulty in teaching and learning multithreaded programming. It consists of a C++ class library and a visualization system. The class library supports many thread management functions and synchronization primitives in an object-oriented way, and the visualization system is activated automatically by a user program and shows the inner working of every thread and every synchronization primitive on-the-fly. Events can also be saved for playback. In this way, students will be able to visualize the dynamic behavior of a threaded program and the interaction among threads and synchronization primitives.

A Unified Approach to Streamline Selection and Viewpoint Selection for 3D Flow Visualization

We treat streamline selection and viewpoint selection as symmetric problems which are formulated into a unified information-theoretic framework. This is achieved by building two interrelated information channels between a pool of candidate streamlines and a set of sample viewpoints. We define the streamline information to select best streamlines and in a similar manner, define the viewpoint information to select best viewpoints. Furthermore, we propose solutions to streamline clustering and viewpoint partitioning based on the representativeness of streamlines and viewpoints, respectively. Finally, we define a camera path that passes through all selected viewpoints for automatic flow field exploration. We demonstrate the robustness of our approach by showing experimental results with different flow data sets, and conducting rigorous comparisons between our algorithm and other seed placement or streamline selection algorithms based on information theory.

Blending two cones with Dupin cyclides

Abstract This paper presents a complete theory of blending cones with Dupin cyclides and consists of four major contributions. First, a necessary and sufficient condition for two cones to have a blending Dupin cyclide is established. Second, based on the intersection structure of the cones, finer characterization results are obtained. Third, a new construction algorithm that establishes a correspondence between points on one or two coplanar lines and all constructed blending Dupin cyclides makes the construction easy and well-organized. Fourth, the completeness of the construction algorithm is proved. Consequently, all blending Dupin cyclides are organized into one to four one-parameter families, each of which is “parameterized” by points on a special line. It is also shown that each family contains an infinite number of ring cyclides, ensuring the existence of singularity free blending surfaces.

On the lower degree intersections of two natural quadrics

In general, two quadric surface intersect in a space quartic curve. However, the intersection frequently degenerates to a collection of plane curves. Degenerate cases are frequent in geometric/solid modeling because degeneracies are often required by design. Their detection is important because degenerate intersections can be computed more easily and allow simpler treatment of important problems. In this paper, we investigate this problem for natural quadrics. Algorithms are presented to detect and compute conic intersections and linear intersections. These methods reveal the relationship between the planes of the degenerate intersections and the quadrics. Using the theory developed in the paper, we present a new and simplified proof of a necessary and sufficient condition for conic intersection. Finally, we present a simple method for determining the types of conic in a degenerate intersection without actually computing the intersection, and an enumeration of all possible conic types. Since only elementary geometric routines such as line intersection are used, all of the above algorithms are intuitive and easily implementable.

A visualization system for multithreaded programming

Almost all modern operating systems, from Windows to Unix, support multithreaded programming. To make sure our students can lead the trend of computer science in the foreseeable future, we need to introduce them to this important technology. However, we have found through experience in teaching multithreaded programming that the paradigm shift from sequential to multithreaded causes students significant problems, such as (1) multithreaded program development requires a new mindset, (2) multithreaded program behavior is dynamic, making debugging very difficult, and (3) proper synchronization is more difficult than anticipated [10, 11]. Moreover, detecting race conditions and deadlocks is more easily said than done.

A tool for teaching curve design

This paper describes a tool for teaching curve design. This tool is a component of the software tools to be used in a computing with geometry course [3, 4] that is being developed under the support of National Science Foundation. Curve design is important in computer graphics, animation, and computer aided design. Unfortunately, curve design requires very involved mathematics even though many curve design concepts are intuitive. As a result, it has been a challenging job for instructors teaching curves and surfaces in computer graphics, computer aided design, and other related courses. During past years, there have not been very many efforts dedicated to curve design tool development. Yen [7] produced a well-received video program explaining important concepts of B-spline curves and surfaces and Rockwood and Chambers [6] published a multimedia tutorial on computer aided geometric design. The former only provides a one-way communication, while the latter restricts users to a predefined environment with very limited interaction for users to carry out experiments. To fill this gap, our tool provides students with a fully interactive environment in which they are free to design, modify, and manipulate curved objects and perform experiments without constraints.In the following, Section 2 presents design issues, Section 3 discusses general features, Section 4 enumerates basic elements, Section 5 covers advanced topics, and Section 6 is our conclusion. Interested readers should consult [1, 2, 5] for mathematical background details.

Computing the intersection of a plane and a natural quadric

Abstract A method of computing the intersection of a plane and a natural quadric surface is presented. This problem is basic in geometric areas such as solid modeling and descriptive geometry. Our method, arising out of recent work on lower degree intersections of quadrics, computes the directions of the axes of the intersection, and then computes their lengths using the Dandelin sphere. The method also gives all parallel plane sections of the natural quadric, with no added computation.

Teaching surface design made easy

All popular computer graphics textbooks have chapters on curves and surfaces [1, 5, 6, 7]. Teaching these chapters could be one of the most challenging tasks in a computer graphics course because of the involved mathematics and the difficulty of visualizing the anticipated effects of the theoretical results. We certainly can skip these chapters and only rely on the polyhedron world, because Gouraud’s or Phong’s shading algorithms could make polyhedra objects appear as realistic curvilinear ones. Unfortunately, real world applications such as ship hull and car body design are usually curvilinear and may only be approximated using polyhedron models. Thus, to address this problem and to make teaching surface design easier, we have designed a pedagogical tool as part of our NSF supported project [8]. One of our goals is to provide the students with an interactive environment which is used to visualize, experiment and verify important and fundamental concepts and algorithms. While there are good textbooks on curve and surface design [3, 4, 9], we can only find two pedagogical aids. Yen’s video program [11] only provides one way information flow. Rockwood and Chambers [10] describe a multimedia tutorial on computer aided geometric design which runs on Windows. It is basically a tutorial that introduces concepts using some animation but lacks a

Multithreaded programming in an introduction to operating systems course

This paper presents a way of teaching multithreaded programming as a component in an introduction to operating systems course. Topics include programming assignments, term projects, and experiences. This paper also suggests future work for overcoming a bottleneck that occurs in the current version of this course.