Steering smog prediction

The use of computational steering for smog prediction is described. This application is representative for many underlying issues found in steering high performance applications: high computing times, large data sets, and many different input parameters. After a short description of the smog prediction model, its visualization and steering are described. The amount of computation needed to solve the governing transport equations is alarmingly high. The user has a large number of options for the display of various aspects of the simulation, and also for the interactive control of its input data. Smooth animation is very important to monitor the evolution of pollutants and for a responsive feedback to parameter changes. Here a performance of least 15 frames per second is required. We discuss techniques that allow the user to steer the numerical solver, such that an optimal tradeoff between computation speed and accuracy can be made

CSE: a modular architecture for computational steering

Computational steering is the ultimate goal of interactive simulation. Steering enables users to supervise and dynamically control the computation of an ongoing simulation. We describe CSE: a modular architecture for a computational steering environment. The kernel of the architecture is designed to be very simple, flexible and minimalistic. All higher level system functionality is pushed into modular components outside of the kernel, resulting in a rich and powerful environment. For these modular components (called satellites) a uniform user interface metaphor for users, based on a tray of cards, has been used. The card tray metaphor is very simple to understand and provides users with a simple mechanism to organize and retrieve the tools. Several applications of the environment are shown

Designing 3D Selection Techniques Using Ballistic and Corrective Movements

The two-component model is a human movement model in which an aimed movement is broken into a voluntary ballistic movement followed by a corrective movement. Recently, experimental evidence has shown that 3D aimed movements in virtual environments can be modeled using the two-component model. In this paper, we use the two-component model for designing 3D interaction techniques which aim at facilitating pointing tasks in virtual reality. This is achieved by parsing the 3D aimed movement in real time into the ballistic and corrective phases, and reducing the index of difficulty of the task during the corrective phase. We implemented two pointing techniques. The ‘AutoWidth’ technique increases the target width during the corrective phase and the ‘AutoDistance’ technique decreases the distance to the target at the end of ballistic phase. We experimentally demonstrated the benefit of these techniques by comparing them with freehand aimed movements. It was shown that both ‘AutoWidth’ and ‘AutoDistance’ techniques exhibit significant improvement on target acquisition time

The effect of varying path properties in path steering tasks

Path steering is a primitive 3D interaction task that requires the user to navigate through a path of a given length and width. In a previous paper, we have conducted controlled experiments in which users operated a pen input device to steer a cursor through a 3D path subject to fixed path properties, such as path length, width, curvature and orientation. From the experimental data we have derived a model which describes the efficiency of the task. In this paper, we focus on studying the movement velocity of 3D manipulation path steering when one or more path properties vary during the task. We have performed a repeated measures design experiment of 8 scenarios, including a scenario in which all path properties were kept constant, 3 scenarios in which the path width, curvature and orientation varied, 3 scenarios of varying two path properties, and 1 scenario of varying all properties. The analysis of our experimental data indicates that a path of varying orientation or width results in a low average steering velocity. During a continuous steering, the joint where a change in path curvature or orientation takes place also significantly decreases the velocity. In addition, path width and curvature are highly-correlated to the average velocity of a segment, i.e. the wider a segment (or the smaller the path curvature), the larger the average steering velocity on that segment. The results of this work could serve as guidelines for designing higher level interaction techniques and better user interfaces for traditional HCI tasks, e.g. 2D or 3D nested-menu navigation

Modeling object pursuit for 3D interactive tasks in virtual reality

Models of interaction tasks are quantitative descriptions of relationships between human temporal performance and the spatial characteristics of the interactive tasks. Examples include Fitts' law for modeling the pointing task and Accot and Zhai's steering law for the path steering task, etc. Models can be used as guidelines to design efficient user interfaces and quantitatively evaluate interaction techniques and input devices. In this paper, we introduce a 3D object pursuit interaction task, in which users are required to continuously track a moving target in a virtual environment. The entire movement of the task is broken into a tracking phase and a correction phase. For each phase, we propose a model that has been verified by two experiments. As the experimental results show, the time for the tracking phase is fixed once a task has been established, while the time for the correction phase usually varies according to some characteristics of the task. It can be modeled as a function of path length, target width and the velocity with which the target moves. The proposed model can be used to quantitatively evaluate the efficiency of user interfaces that involve the interaction with moving objects

Porting a visualization package from IRIX to NT : what will I get, what will I pay?

We discuss our experiences in porting a moderately large scientific visualization environment from IRIX to NT~4.0. Two porting strategies have been taken: a port via a POSIX emulation layer and a native NT port. POSIX compliant code can be ported to NT with relatively little effort if the code adheres to general accepted programming principles, such as modularity and encapsulation. The performance of a modern 3D Wintel machine is quite satisfactory for a variety of scientific desktop tasks. We have compared the performance of a 2 CPU Dell OptiPlex with FireGL 4000 graphics option to various SGI desktop workstations