6217383
Haptic interaction with fluid media
We present a method for integrating force feedback with interactive fluid simulation. We use the method described to generate haptic display of an incompressible Navier-Stokes fluid simulation. The force feedback calculation is based on the equations of fluid motion, and enables us to generate forces as well as torques for use with haptic devices capable of delivering torque. In addition, we adapt our fluid-haptic feedback method for use in a painting application that is based on fluid simulation, enabling the artist to feel the paint. Finally we describe a force filtering technique to reduce the artifacts that result from using 60Hz simulation data to drive the 1KHz haptic servo loop, a situation which often arises in practice.
7169150
A versatile interactive 3D brush model
We present a flexible modeling approach capable of realistically simulating many varieties of brushes commonly used in painting. Our geometric model of brush heads is a combination of subdivision surfaces and hundreds of individual bristles represented by thin polygonal strips. We exploit bristle-to-bristle coherence, simulating only a fraction of the bristles and using interpolation for the remainder. Our dynamic model incorporates realistic physically-based deformation, including anisotropic friction, brush plasticity, and tip spreading. We use an energy minimization framework with a novel geometric representation of the brush head to generate a wider variety of brushes. Finally, we have developed an improved haptic model that provides realistic force feedback, directly related to the results of the brush dynamic simulation. Using this model, we are able to simulate a wide range of brush styles and create an excellent variety of strokes such as the crisp, curvy strokes of Western decorative painting, or rough scratchy strokes like certain Oriental calligraphy. We have also developed an exporter for a popular free 3D modeling package that makes it easier for non-programmers to create any desired style of brush, real or fanciful.
7639620
Stable and responsive six-degree-of-freedom haptic manipulation using implicit integration
In this paper we present a novel approach for simulating the rigid body dynamics of a haptically manipulated object using implicit integration. Our formulation requires the linearization of contact and manipulation forces, and it provides higher stability and responsiveness than previous methods. The linearization of contact forces, coupled with fast, perceptually based collision detection algorithms, enables us to perform highly stable and responsive 6-degree-of-freedom haptic rendering of complex polygonal models.
206451107
Sensation-Preserving Haptic Rendering
Most human-computer interactive systems focus primarily on the graphical rendering of visual information and, to a lesser extent, on the display of auditory information. Haptic interfaces have the potential to increase the quality of human-computer interaction by accommodating the sense of touch. They provide an attractive augmentation to visual display and enhance the level of understanding of complex data sets. A haptic rendering system generates contact or restoring forces to prevent penetration into the virtual objects and create a sense of touch. The system computes contact forces by first detecting if a collision or penetration has occurred. Then, the system determines the (projected) contact points on the model surface. Finally, it computes restoring forces based on the amount of penetration. Researchers have recently investigated the problem of rendering the contact forces and torques between 3D virtual objects. This problem is known as six-degrees-of-freedom (6-DOF) haptic rendering, as the computed output includes both 3-DOF forces and 3-DOF torques. This article presents an overview of our work in this area. We suggest different approximation methods based on the principle of preserving the dominant perceptual factors in haptic exploration.
9041268
Modeling ice dynamics as a thin-film Stefan problem
Large, 3D ice formations such as icicles exhibit a high degree of geometric and optical complexity. Modeling these features by hand can be a daunting task, so we present a novel physically-based algorithm for simulating this phenomenon. Solidification is usually posed as a so-called 'Stefan problem', but the problem in its classic form is inappropriate for simulating the ice typically found in a winter scene. We instead use the 'thin-film' variant of the Stefan problem to derive velocity equations for a level set simulation. However, due to the scales involved in the problem, even an adaptive grid level set solver is still insufficient to track the tip of an icicle. Therefore, we derive an analytical solution for the icicle tip and use it to correct the level set simulation. The results appear to be in agreement with experimental data. We also present a physically-based technique for modeling ripples along the ice surface that alleviates the need to explicitly track small-scale geometry. To our knowledge, our approach is the most complete model available, and produces complex visual phenomena that no previous method has been able to capture.
6243696
Geometry-driven physical interaction between avatars and virtual environments
We present an interactive technique on virtual contact handling for avatars in virtual environments using geometry-driven physics. If a contact has occurred between an articulated avatar and a virtual environment, the global penetration depth and contact points are estimated based on a fast local penetration depth computation for decomposed convex pieces. The penetration depth and contact information are then used to resolve overlap between the avatar and the virtual environment. If applicable, joint angles for an articulated body are computed using an inverse kinematics approach based on cyclic coordinate descent. Resulting dynamic response with friction is modeled with impulse-based dynamics under the Coulomb friction law. We demonstrate the algorithm on a modestly complex virtual environment. The resulting system is able to maintain an interactive frame rate of 30–60 Hz. Copyright © 2004 John Wiley & Sons, Ltd.
17862666
Virtual Interaction for Effective E-Learning
This research investigates whether information technologies, such as automated question answering (QA), can add interactivity into a multimedia-based e-learning system, as well as how this type of virtual interaction affects the effectiveness of e-learning. Based on a review of multiple learning theories and technologies, an exploratory model for studying the effectiveness of interactive e-learning, Learning with Virtual Mentors (LVM), is proposed and a prototype system is developed to implement the LVM model. A series of studies, including a controlled experiment and surveys, have been conducted to explore the relationships among the core constructs of the LVM model: learning phases, system interactivity, learning activity, and learning outcomes. Findings indicate that virtual interaction positively impacts student behaviors by encouraging students to interact more and increasing student satisfaction with the learning process; however, the correlation between virtual interaction and actual learning performance is limited. Consequently, the LVM model needs to be further explored and developed.
986758
The Interaction of Research Methods for System Evaluation and Theory Testing: A New Vision of the Benefits of Multi-Methodological Information Systems Research
A number of multi-methodological Information Systems research frameworks have been proposed to guide research in the IS field. In this paper, we describe a three-year program of research evaluating a computerbased training system for deception detection (Agent99 Trainer) using one such multi-methodological IS framework. The process and results of this research program clearly demonstrate the benefits of combining and triangulating multiple research methods. Moreover, through the experiences in the Agent99 Trainer study, we discover two different types of interactions between the research methods that were applied in this study. One of the interactions is between the results from different methods, while the other is between the results and the methods themselves. Hence, we propose an extended interpretation of multi-methodological IS research frameworks to incorporate these two types of interactions between research methods. We argue that this extended interpretation will provide a more specific explanation for why the triangulation among multiple research methods can provide benefits to IS research.
2903221
Algorithms for clique-independent sets on subclasses of circular-arc graphs
A circular-arc graph is the intersection graph of arcs on a circle. A Helly circular-arc graph is a circular-arc graph admitting a model whose arcs satisfy the Helly property. A clique-independent set of a graph is a set of pairwise disjoint cliques of the graph. It is NP-hard to compute the maximum cardinality of a clique-independent set for a general graph. In the present paper, we propose polynomial time algorithms for finding the maximum cardinality and weight of a clique-independent set of a 3K2-free CA graph. Also, we apply the algorithms to the special case of an HCA graph. The complexity of the proposed algorithm for the cardinality problem in HCA graphs is O(n). This represents an improvement over the existing algorithm by Guruswami and Pandu Rangan, whose complexity is O(n2). These algorithms suppose that an HCA model of the graph is given.
205481590
Fast and simple algorithms to count the number of vertex covers in an interval graph
This study provides the following fast and simple algorithms for an interval graph: (1) an algorithm for counting the number of vertex covers, and (2) an algorithm for counting the number of minimal vertex covers.
45057698
The distributed program reliability analysis on star topologies
Abstract A distributed computing system consists of processing elements, communication links, memory units, data files, and programs. These resources are interconnected via a communication network and controlled by a distributed operating system. The distributed program reliability in a distributed computing system is the probability that a program which runs on multiple processing elements and needs to retrieve data files from other processing elements will be executed successfully. This reliability varies according to (1) the topology of the distributed computing system, (2) the reliability of the communication edges, (3) the data files and programs distribution among processing elements, and (4) the data files required to execute a program. In this paper, we show that computing the distributed program reliability on the star distributed computing systems is NP-hard. We also develop an efficiently solvable case to compute distributed program reliability when some additional file distribution is restricted on the star topology. Scope and purpose Recent advances in VLSI circuitry have a tremendous impact on the price-performance revolution in microelectronics. This development has led to an increased use of workstations connected in the form of a powerful distributed computing system. Potential benefits offered by such distributed computing systems include better cost performance, enhanced fault tolerance, increased system throughput, and efficient sharing of resources. Distributed program reliability is an important measure that should be examined for designing a high fault-tolerance distributed computing system. This reliability varies according to (1) the topology of the distributed computing system, (2) the reliability of the communication edges, (3) the data files and programs distribution among processing elements, and (4) the data files required to execute a program. This article is concerned with the analysis of distributed program reliability on star distributed computing systems.