Paul Heinzlreiter

Visualization services on the grid: The grid visualization kernel

Two important tools of todays science and engineering are computational grids and visualization. While grid infrastructures offer a means to process large amounts of data across different, possibly distant resources, visualization aids in understanding the meaning of data. The Grid Visualization Kernel (GVK) addresses the connection of grid applications and visualization clients on the grid. The visualization capabilities of GVK are provided as flexible grid services via dedicated interfaces and protocols, while GVK itself relies on Globus services to implement the functionality of the visualization pipeline. This paper describes the concept of GVK and its core functionality for grid visualization services, and discusses how to use visualization in the grid environment.

Grid-Enabled Visualization with GVK

The present status of visualization on the grid is not really satisfying. In contrast to other grid services, such as batch processing, data transfer, and resource scheduling, visualization is still utilized in the traditional point-to-point fashion, with applications integrating visualization as subroutine calls or even post-mortem. This situation is addressed by the Grid Visualization Kernel GVK, which proposes a fully grid-enabled approach to scientific visualization. The infrastructure of GVK features a portal for arbitrary simulation servers and visualization clients, while the actual processing of the visualization pipeline is transparently performed on the available grid resources.

Optimizations in the grid visualization kernel

Computational grids are large-scale computing infrastructures, which offer ubiquitous access to networked resources for integrated and collaborative use by multiple organizations. The required abstraction and management for grids is transparently performed in the grid middleware layer. An example is the Grid Visualization Kernel GVK, which supports distributed near real-time interaction between distant simulation servers and visualization clients. Efficient transportation of data via limited and varying bandwidth is achieved by applying optimized abstraction and filtering techniques. The basic idea is to incorporate knowledge about visualization data structures and user viewpoints before transferring the data between server and client. Corresponding ideas include optimizations like multiple levels of detail, occlusion-culling, reference and image-based rendering.

Interactive Virtual Reality on the Grid

The grid has received a substantial amount of interest (and funding) over the past few years, even though the majority of grid applications are still batch-oriented. For this reason, extensions to grid middleware are a basic necessity to advance the idea of the grid into new application domains. The glogin tool and its integration into the Grid Visualization Kernel (GVK) yield both, interactivity and visualization, into the grid. While glogin enables the tunneling of arbitrary interactive traffic in and out of the grid, GVK offers transparent visualization services for grid applications while exploiting the grid’s performance for time-consuming visualization tasks. In this paper, the utilization of glogin and GVK is demonstrated for Virtual Reality (VR) environments. Two distinct approaches for VR, using either abstract visualization objects or video streams, are explained, highlighting advantages and disadvantages of each.

An adaptive network architecture for close-coupled collaboration in distributed virtual environments

This paper describes a network architecture for large-scale, interactive, distributed 3D environments. Its main goals are the maintenance of low latency during user interaction and fast broadcasting techniques in order to fulfill consistency requirements. The main purpose is supporting close-coupled collaboration within a large virtual environment. Additionally the network topology adapts itself to varying amounts of users and computers connected to the system.

Navigation models for a flexible, multi-mode VR navigation framework

Navigation is a key issue for Virtual Reality (VR) applications because it forms an integral part of the feeling of presence, which should be conveyed by VR applications. This paper presents several VR navigation modes which are useful for orientation and interaction in Virtual Environments (VEs). Due to the existence of different kinds of applications several navigation modes are required.

Interactive Virtual Reality Volume Visualization on the Grid

Grid computing evolves into a standard method for processing large datasets. Consequently most available grid applications focus on high performance computing and high-throughput computing. The interactive visualization of the acquired simulation results can be performed directly on the grid using the Grid Visualization Kernel GVK, which is a grid middleware extension built on top of the Globus Toolkit. An example is the visualization of volume data within Virtual Reality environments, where the data for visualization is generated somewhere on the grid, while the user explores the visual representation at some other place on the grid.

Int.eu.grid

The int.eu.grid project aims to provide a production quality grid computing infrastructure for e-Science supporting parallel and interactive applications. The infrastructure capacity is presently about 750 cores distributed over 12 sites in 7 countries, and it implies a much larger management and coordination effort to guarantee high availability and fast start-up mechanisms of (batch and parallel) interactive applications. Int.eu.grid is also strongly focused on providing a user-friendly access to the grid through a powerful GUI allowing a transparent access to grid resources and the possibility to interact in real time with running applications. In this chapter we present the management policies, infrastructure services, and operation mechanisms that enable interactivity over the grid bringing a new added value to grid environments.

Scheduling and Resource Brokering within the Grid Visualization Kernel

The role of grid computing as a tool for computational science which has evolved over the past years leads to additional requirements for grid middleware. One of these requirements is visualization support which is provided by the Grid Visualization Kernel (GVK). To enable proper usage of grid resources for visualization purposes sophisticated scheduling and resource brokering mechanisms are required. These mechanisms enable the automatic construction of a visualization pipeline taking into account the requirements specified by the user as well as resource availability.

MCE–CAVE: program for interactive visualization of electron density maps within the CAVE virtual-reality environment

Department of Solid State Chemistry, Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic, Institute of Physical Biology, Novy ZaÂmek 136, 373 33 Nove Hrady, Czech Republic, and Department for Graphics and Parallel Processing (GUP), Institute of Technical Computer Science and Telematics, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria. Correspondence e-mail: husakm@vscht.cz