Immersive ParaView: A Community-based, Immersive, Universal

Scientific Visualization Application

Nikhil Shetty

Kitware Inc.

Aashish Chaudhary

Kitware Inc.

Daniel Coming

Desert Research Institute

William R. Sherman∗

Indiana University

Patrick O’Leary

Idaho National Laboratory

Eric T. Whiting

Idaho National Laboratory

Simon Su

National Oceanic and Atmospheric Administration

ABSTRACT

The availability of low-cost virtual reality (VR) systems coupledwith a growing population of researchers accustomed to newer in-terface styles makes this a ripe time to help domain science re-searchers cross the bridge to utilizing immersive interfaces. Thelogical next step is for scientists, engineers, doctors, etc. to incor-porate immersive visualization into their exploration and analysisworkflows. However, from past experience, we know having accessto equipment is not sufficient. There are also several software hur-dles to overcome. Obstacles must be lowered to provide scientists,engineers, and medical professionals low-risk means of exploringtechnologies beyond their desktops.

Index Terms: I.3.7 [COMPUTER GRAPHICS]: Three-Dimensional Graphics and Realism—Virtual Reality; I.3.4 [COM-PUTER GRAPHICS]: Graphics Utilities—Virtual device inter-faces; I.6.3 [SIMULATION AND MODELING]: Applications—Immersive Visualization;

1 INTRODUCTION

1989 was the breakthrough year in which virtual reality (VR) tech-nology became increasingly available, spreading through manycomputer science and scientific research labs. From the outset, thisnew medium was frequently combined with the also nascent fieldof scientific visualization [3]. Yet, an open-source, robust, gen-eral purpose visualization tool that permits the seamless movementfrom desktop to immersive environments has been an elusive target.

Lacking good immersive visualization software, many developone-off applications serving an immediate need. The results is ap-plications that are either locked to specific hardware, restricted to agiven VR toolkit, or tied to a specific student’s thesis work. Thusthere are significant advantages for taking a general purpose open-source visualization tool, ParaView [2], and integrating immersiveinteraction features directly into its framework. With the advent ofconsumer 3D TV’s, and affordable tracking technologies, immer-sive environments are becoming increasingly democratized. Par-aView’s new immersive interaction capability offers a freely avail-able visualization solution for a highly effective emerging technol-ogy. Immersive ParaView is designed to take advantage of a re-searcher’s current workflow and extend, rather than replace it.

2 OBJECTIVES

As the practice of scientific visualization continues to advance, vi-sualization packages have gone in and out of use. The flux of vi-sualization packages and the flux of immersive interface librarieshave combined to hamper the success of promulgating immersivevisualization to a wide audience. With VTK as a prevailing open-source visualization system, and ParaView a standardized interface

∗e-mail: shermanw@indiana.edu

to VTK, half the uncertainty of immersive visualization can be re-moved. The history of immersive visualization efforts informs usthat breaking from the core of the library versus using it as-is wouldfurther erode adoption, thus our efforts avoid the requirement of us-ing non-vanilla ParaView.

So we set out with three major objectives in mind: to be wellused, to be impactful, and to be sustainable for the long term.There are several tactics we are pursuing to reach our objectives.Clearly open-source is important – the landscape of past effortsalong these lines is strewn with the carcases of efforts that died pri-marily due to their closed nature. We also recognize that to builda community of sufficient size the tool should be general purpose.Just as important as ease of use is good documentation (easy stepsare hard to do if you have to guess what they are). Documenta-tion should also include tutorials on building and using the system.Hence, our selection to build upon ParaView our objectives.

3 ARCHITECTURE

The Visualization Toolkit is an open-source freely available soft-ware system for visualization, image processing, and 3D computergraphics. VTK supports a wide variety of visualization algorithmsand modeling techniques. ParaView [1] is an open-source, multi-platform visualization application, built on VTK. It supports dis-tributed computation models to process large datasets, and it pro-vides a graphical user interface allowing researchers to quicklyinteract with data. Like VTK, ParaView is supported and devel-oped by a large international community of domain researchers andvisualization experts. It accommodates molecular, finite-element,finite-difference simulation results and more, handling an extensiveset of standardized and domain-specific data formats.

A primary goal of ParaView is to develop an extensible architec-ture based on open standards. Our implementation brings ParaViewinto VR. Along with this comes ParaView’s ability to transcend andscale across various hardware. This means that ParaView can nowscale from a thin client to a 6-sided CAVE-like display.

In the standard ParaView architecture, users create visual-ization pipelines locally or remotely and interact with data viamouse/keyboard using the GUI Client or other user interfaces (e.g.,application or web client). The Server Manager then takes theseevents and sends commands to a set of parallel Render Servers andData Servers which it manages either across a network or on a sin-gle machine, using the abstraction of proxies: client-side represen-tations of distributed server-side objects.

The Data Server reads raw data, applies filter algorithms to itand sends it to file and/or Render Servers. For larger data sets, itsupports shared memory and distributed parallelism via the mes-sage passing interface library (MPI). The Render Servers supportparallel processes rendering portions of the data, which are thencomposited into a single image.

3.1 Porting ParaView to support VR

In porting ParaView to VR, we were faced with addressing: 1) howto support multiple displays in the current framework without com-

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promising the essence of ParaView? 2) how to deal with deviceinputs (especially head tracking data) to drive interactions?

We chose the Render Server to drive the VR displays. The Ren-der Server was intended for parallel rendering and image composit-ing. However it can also be perceived as a framework where mul-tiple views of the same data can be rendered synchronously on dif-ferent machines (Figure 1) as in many typical VR displays.

Figure 1: The ParaView architecture adapted for VR. The client per-forms both the tracking and rendering control.

The ParaView client receives tracking data from the VRPN [4]tracking server. The Client performs a dual role as a client, forboth the VRPN and the Render Servers, and as a router, routingtracking data from the VRPN server to every Camera (Figure 1).Tracking information is set in the Camera Proxy on the client-sidewhich in turn propagates to the cameras for each display. Eachcamera combines this information with the display configurationparameters to calculate its appropriate projection.

Perspective-corrected rendering posed a challenge. While Par-aView supports stereoscopic rendering, the Camera Object in Par-aView/VTK lacked off-axis projection. Thus, the VTK Camera wasmodified to support off-axis projections based on the user’s head-tracked position.

3.2 Innovations

The innovations of this work are: 1) porting ParaView to work withimmersive environments; 2) enabling users to migrate visualizationsessions between laptops and immersive environments; 3) leverag-ing a mixed desktop and immersive interfaces; and 4) developing aflexible, network-based visualization architecture.

Immersive ParaView adds physical interaction while preserv-ing the data streaming and data parallel mechanisms in ParaViewfor large data visualization along with other ParaView cababilities.

Visualization Session Migration leverages ParaView’sclient/server model paired with VR hardware abstraction to allowusers to connect on the fly to a VR system. Users can migratebetween multiple sessions of desktops and CAVEs with the sessionstate preserved. Thus, Immersive ParaView enhances flexibilityand lowers barriers for exploring immersive visualization.

Mixed Interfaces arise when the ParaView client runs on a touchdevice in an immersive environment such as a CAVE. The VR dis-play acts as a server, while the a touch tablet or screen acts as aclient to control the visualization. The advantage of physical im-mersion and three-dimensional interfaces are combined with finecontrol of traditional two-dimensional widgets via the fingers al-lowing the most appropriate interface to be used for a given task.

A Network-Based Visualization Architecture supports multi-ple web clients connecting to the same visualization session, there-fore promoting collaboration.

4 RESULTS AND FUTURE DIRECTIONS

We tested this version of ParaView using several different immer-sive environments including a 4-sided CAVE, a 6-sided CAVE, anda low-cost display based on commercial off-the-shelf parts.

Figure 2: The user controls the immersive visualization through anintegrated touchscreen device.

The 4-sided CAVE was tested using a single render server withtwo NVidia QuadroPlex’s. The 6-sided tiled CAVE was tested us-ing a 12-node cluster. The low-cost display consists of a 3D readyTV and optical tracking. All the Immersive ParaView features areplanned to be available in the standard distribution of ParaView re-lease after more extensive testing.

Collaboration is currently possible between members in sin-gle VR setup and a desktop client. With the integration of Par-aViewWeb, additional clients would be able to join into a sessionand collaborate via a web browser. Furthermore, enabling CAVE-to-CAVE collaboration scenarios is a long term goal of this project,and is part of our roadmap for Immersive ParaView’s framework.

In terms of interactions, ParaView currently does not have welldefined Interactor Styles for 3D input devices. In addition, we havenot defined the elements of the architecture that will enable the useof multiple interaction devices. A comprehensive solution will needto be designed and implemented to support these features.

5 CONCLUSION

Effective immersive visualization tools have long held an allure fortheir potential to improve scientific workflows. With ubiquitous im-mersive systems on the horizon, increasingly available low-cost VRsystems, and the maturation of a popular open-source visualizationsystem, the time is ripe for creating a general purpose immersivevisualization system. Immersive ParaView takes strides towards afully-featured, open-source visualization system that can leverageimmersive technologies to serve broad scientific communities. Itoffers a low barrier to entry, drawing users to immersive displaysthrough familiar software and migrating visualization sessions. Asit attracts a user community, we expect Immersive ParaView to be-come sustainable, gain support, and raise awareness and utilizationof VR displays. Ultimately, we aim to improve scientific workflowsas low-cost VR systems and Immersive Paraview and similar toolsbecome integral components in scientists’ labs.

ACKNOWLEDGEMENTS

The authors would like to thank Kitware Inc., DRI, INL, IU forfacilities and support. This work was supported in part through theINL LDRD Program under DOE Idaho Operations Office ContractDE-AC07-05ID14517.

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