Desmond Germans

The distributed ASCI Supercomputer project

The Distributed ASCI Supercomputer (DAS) is a homogeneous wide-area distributed system consisting of four cluster computers at different locations. DAS has been used for research on communication software, parallel languages and programming systems, schedulers, parallel applications, and distributed applications. The paper gives a preview of the most interesting research results obtained so far in the DAS project.

VIRPI: a high-level toolkit for interactive scientific visualization in virtual reality

Research areas that require interactive visualization of simulation data tend to dismiss virtual reality due to the lack of accessible tools for application specialists. This paper presents an integral toolkit for interactive visualization in virtual reality environments. The toolkit defines a framework to build applications that allow the user to interact with arbitrary simulation software and describe virtual measurement tools for the visualized data. The approach is illustrated with a case study in medical imaging.

Griz : experience with remote visualization over an optical grid

This paper describes the experiments of remote rendering over an intercontinental optical network during the iGrid2002 conference in Amsterdam from September 23 to 26. A rendering cluster in Chicago was used to generate images which were displayed in real-time on a 4-tile visualization setup in Amsterdam. On average, one gigabit per second (1 Gbps) was consumed to enable remote visualization, at interactive frame rate, with a 1600 × 1200 pixels configuration.

CAVEStudy: an infrastructure for computational steering in virtual reality environments

We present the CAVEStudy system that enables scientists to interactively steer a simulation from a virtual reality (VR) environment. No modification to the source code is necessary. CAVEStudy allows interactive and immersive analysis of a simulation running on a remote computer. Using a high-level description of the simulation, the system generates the communication layer (based on CAVERN-Soft) needed to control the execution and to gather data at runtime. We describe three case-studies implemented with CAVEStudy: soccer simulation, diode laser simulation and molecular dynamics.

Measuring in Virtual Reality: A Case Study in Dentistry

For application specialists to accept virtual reality (VR) as a valid new measuring environment, we conducted several case studies. This paper describes a case study in dentistry in which VR is used to measure the length of the root canal of a tooth from processed tomography data. This paper shows the advantages of measuring in visualization space rather than in reality. We present a software framework aimed at the application specialist rather than the VR expert. Furthermore, the VR measuring technique is analyzed and compared to traditional measuring techniques for this particular application. We show that VR allows for intuitive measuring paradigms that are accurate and versatile alternatives to situations where traditional techniques are deficient.

CAVEStudy: An Infrastructure for Computational Steering and Measuring in Virtual Reality Environments

We present the CAVEStudy system that enables scientists to interactively steer a simulation from a virtual reality (VR) environment. No modification to the source code is necessary. CAVEStudy allows interactive and immersive analysis of a simulation running on a remote computer. Using a high-level description of the simulation, the system generates the communication layer (based on CAVERNSoft) needed to control the execution and to gather data at runtime. We describe three case-studies implemented with CAVEStudy: soccer simulation, diode laser simulation, and molecular dynamics. In addition, we briefly describe a new technique of virtual measuring which closes the loop between simulation, immersive visualization, interaction in simulation domain and steering, giving the scientist deeper insight into the simulated phenomenon.

Man multi-agent interaction in VR: a case study with RoboCup

We discuss the use of virtual reality (VR) techniques for interaction between humans and a multi-agent system in the context of RoboCup. The goal of RoboCup is to let teams of cooperating autonomous agents play a soccer match, using either robots or simulated players. We use RoboCup to study distributed collaborative applications, which allow multiple users at different geographic locations to cooperate, by interacting in real time through a shared simulation program. Our objective is to construct a VR environment in which humans at different locations can play along with a running RoboCup simulation in a natural way. The simulation system consists of the Soccer Server and a set of processes modeling the players. The server keeps track of the state of the game: provides the players with information on the game, and enforces the rules. The players request state information and autonomously calculate a behavior, sending the server commands that consist of accelerations, turns and kicks. The server discretizes time into slots, only one command is executed per time slot. We have developed a 3D visualization system that allows a user in a CAVE to interact with the soccer simulation software.

Real-time, adaptive measurement of corneal shapes

Conventional tools for measuring the shape of the cornea perform poorly when applied to abnormal eyes. The image processing regularly fails, and the shape reconstruction often produces inaccurate results. This article describes a single measurement instrument that could integrate real-time solutions to both problems.

Lessons learned from building and calibrating the ICWall, a stereo tiled display: Research Articles

Parallel rendering, visibility culling and level-of-detail are key techniques to improve the rendering performance for large geometric data sets. Although each of these techniques has been researched extensively and some systems have been developed to combine them together. However, parallel occlusion culling, that is distributing the computation of occlusion culling to multiple computing nodes such as a CPUs cluster or a GPUs cluster, has rarely been touched. This is because most existing occlusion culling algorithms are difficult to parallelize or do not scale well when parallelized. We first introduce a novel occlusion culling algorithm that uses the occlusion query functionality provided by current GPU. We employ a visibility prediction technique based on temporal coherence to reduce the times of occlusion query. Furthermore, different strategies of parallelizing the occlusion culling algorithm on a GPUs cluster are proposed including data parallelism strategies and functionality parallelism strategies. Data parallelism strategies decompose the data sets for occlusion query into disjoint parts and map these queries on different cluster nodes for parallel execution while functionality parallelism strategies assemble an occlusion culling pipeline with multiple cluster nodes which outputs image stream steadily. We propose a number of solutions to some special issues on parallelizing this occlusion culling algorithm, such as the transferring of data dependency and the load-balancing of occlusion culling pipeline. Experimental results demonstrate the efficiency of the proposed parallelism strategies of the occlusion culling algorithm based on the visibility predictor. Copyright

Lessons learned from building and calibrating the ICWall, a stereo tiled display

Implementation of stereo tiled displays is a rather demanding task. In this article we want to share the lessons we have learned during the design and construction of the ICWall tiled display. This large display, used in a classroom setting, is a high‐resolution stereo tiled display (2 × 8 tiles), built from low‐cost commodity components. The overall image is produced by an array of projectors. When building such a system, a key challenge is to align the projector images. We describe our automated approach for alignment/calibration of the left‐ and right‐eye stereo images. We provide measurements that show accuracy of this procedure. We explain and compare two calibration approaches: a single‐pass and a two‐pass rendering method to align the tiled images. We explain how to provide seamless image on the tiled display and which issues have to be solved. We also discuss the depth perception issues on the ICWall for the large audiences. Another important aspect, is the architecture of the software used for PC‐cluster‐based rendering. We describe Aura, the parallel scene graph API that is used for rendering on our tiled display. Copyright