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Envisioning Information Lecture 16 – Distributed and Collaborative Visualization

Envisioning Information Lecture 16 – Distributed and Collaborative Visualization. Ken Brodlie kwb@comp.leeds.ac.uk. Outline of Lecture. From Visualization to Computational Steering Distributed visualization Extending dataflow across the network

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Envisioning Information Lecture 16 – Distributed and Collaborative Visualization

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  1. Envisioning Information Lecture 16 – Distributed and Collaborative Visualization Ken Brodlie kwb@comp.leeds.ac.uk ENV 2006

  2. Outline of Lecture • From Visualization to Computational Steering • Distributed visualization • Extending dataflow across the network • Grid-based visualization and computational steering • Collaborative visualization • Sharing the display screen • Sharing the visualization ENV 2006

  3. Visualization represented as pipeline: Read in data Construct a visualization in terms of geometry Render geometry as image Realised as modular visualization environment IRIS Explorer is one example Visual programming paradigm Extensible – add your own modules visualize data render http://www.nag.co.uk Dataflow Visualization Systems ENV 2006

  4. Visualization Software Environments • IRIS Explorer is one of a family of similar visualization systems • First product was AVS • Still major player but no longer visual programming • http://www.avs.com • Amira, IBM Open Visualization Data Explorer (DX), IRIS Explorer • visual programming based : plug, play, throw away • application decomposed as set of modules, configured at run-time (blur between building and running an application) • open : user can write modules • low-cost ENV 2006

  5. IBM Open Visualization Data Explorer – now OpenDX • Released around 1991 by IBM • Made open source in 1999 • www.opendx.org • A major use of it has been for weather visualization http://www.research.ibm.com/weather/ ENV 2006

  6. More recent product Increasing use for medical applications.. .. But also engineering including CFD Marketed by TGS www.tgs.com Amira ENV 2006

  7. vtk is a programming - based toolkit Open source C++ library www.kitware.com vtk - Visualization Toolkit ENV 2006

  8. .. And there are many others http://www.kdnuggets.com/software/visualization.html ENV 2006

  9. IRIS Explorer - Creating Your Own Modules • It is possible to create your own modules • The mbuilder tool creates a wrapper around your own code • See: http://www.nag.co.uk/visual/ie/iecbb/doc/html/unix-iemwg5-0.htm ENV 2006

  10. Scripting - skm • IRIS Explorer can be driven either by GUI or by command line interface • Commands can be grouped as a ‘script’ that IRIS Explorer runs • explorer -script <file> • This allows Explorer to be run in batch mode, or to be driven by another application • The scripting language is called Skm (pronounced as ‘scheme’) • Can be used interactively… • … in linux • explorer -script % • … in Windows, • use Skm editor (view menu) ENV 2006

  11. Creating a Simple Script • To launch a module: (start “ReadImg”) (start “DisplayImg”) • To connect ports: (connect “ReadImg” “Output” “DisplayImg” “Input”) • To start a map: (start-map “cfd”) • See chapter 6 of User Manual on Web http://www.nag.co.uk/visual/ie/iecbb/doc/html/unix-ug-chap06.htm ENV 2006

  12. Visualization and Simulation • Visualization is a key tool in understanding the results of numerical simulations of complex physical phenomena • Different modes of combining simulation and visualization: • Post-processing • Tracking • Steering ENV 2006

  13. Post-processing Do the simulation and store results (step 1) Look at the results in a separate process (step 2) Revise the simulation (back to step 1) visualize data render simulation Linking Visualization and Simulation – Post Processing Step 1 Step 2 PRO: study at your own pace CON: must finish simulation first ENV 2006

  14. Tracking Exploit extensibility of the dataflow visualization environment by including the simulation in the pipeline Track the behaviour of simulation as it runs visualize render simulate Linking Simulation and Visualization - Tracking PRO: can abort fruitless simulations ENV 2006

  15. simulate visualize control render Linking Simulation and Visualization - Steering • Computational steering: • By including a control module in the pipeline, we can direct the simulation in response to the visualization PRO: not only can we track, we can alter the actual course of the simulation ‘Human-in-the-loop’ ENV 2006

  16. Early visualization systems all have this extensibility feature and so can be used for steering IRIS Explorer for example New systems have emerged specifically to support steering SCIRun from Utah Pressure profile for EHL contact Computational Steering Environments ENV 2006

  17. An explosion! A dangerous chemical escapes! Where is the fugitive pollutant headed? Who needs to be evacuated? Imagine this …. ENV 2006

  18. Model the dispersion by solving system of PDEs Understand solution by visualization What if scenarios … need to be able to steer the simulation For example, what if the wind changes direction? Understanding What Will Happen ENV 2006

  19. Tracking the Pollution ENV 2006

  20. What can be Steered? • Steering requires the writer of the simulation code to expose parameters that can be legitimately modified in the course of a run • frequency of output of results • values of external influences that may vary over a simulation • Not all parameters can be changed • time step used by numerical codes to achieve stability and/or accuracy • Notion of backtracking is important in some simulations • Often you first observe, then wish to rewind a few timesteps, then replay with different parameter settings ENV 2006

  21. Our Scenario • We shall use this scenario to illustrate: • Distributed visualization : we need to understand where the pollutant is headed in faster than real-time … therefore we need to run the simulation on a powerful compute resource • Collaborative visualization : there is no time to collocate the scientist, the meteorologist, the politician or whoever needs to be involved … so we need to link people in over the network to allow them to visualize collaboratively … while still using IRIS Explorer! ENV 2006

  22. Select remote host Harnessing Remote Compute Resources – Grid Computing Explorer on multiple hosts Explorer on single host • Automatic authentication using: • Globus certificate • SSH Key pair ENV 2006

  23. Simulation Runs Remotely ENV 2006

  24. A Tale ENV 2006

  25. The Monkey Gets the Nuts – Two Heads ARE Better than One Thanks to Accra Academy, Ghana ENV 2006

  26. Radical collocation has proved highly successful in a number of areas Space missions Safety critical software development Productivity doubled Teasley et al, Univ of Michigan But this requires: Social disruption Advance planning … and can end in tears Can we gain at least part of this success using electronic collaboration? Collaborative Working ENV 2006

  27. We need to move away from seeing collaborative visualization as a group around a display screen.. .. Towards collaboration over a network Collaborative visualization Visualizing Collaboratively ENV 2006

  28. Collaborating in the Pollution Demonstrator • Who needs to collaborate and in what way? • Scientists and numerical modellers • Discuss amongst each other possible scenarios • Discuss need to pull in further Grid resources perhaps • Meteorologist • Will play an active part in controlling the simulation • Environmental agency decision makers • Need to analyse ‘what-if’ scenarios and construct presentations for politicians • Politicians, local authorities • Want to see clear presentation of consequences • Probably not interested in steering ENV 2006

  29. visualize visualize data data render render Sharing the Display Screen • A very simple model is to broadcast the display screen of an application to a set of (passive) users • Operating system level • Screen image is broadcast using intelligent compression • Only active user can enter input User A executes application internet User B receives copy of user A desktop - does not execute application ENV 2006

  30. Sharing the Display Screen • There are a number of available technologies for screen sharing • VNC – Virtual Network Computing • Family of open source products evolved from original VNC development by AT&T • RealVNC : www.realvnc.com (original development team) • tightVNC : www.tightvnc.com (new compression algorithms) • Heterogeneous • Microsoft NetMeeting (and now MSN Messenger) ENV 2006

  31. Sharing Display Screen • Advantages • Very simple concept – works for any application • Good for training • Good for presentation to a group • Disadvantages • No independent working • Performance issues when rapid screen changes • Variations • (1) Only one master – only one can control by mouse and keyboard input • (2) Any participant can input ENV 2006

  32. Sharing the Visualization • This is a more flexible approach – and specific to dataflow visualization • Each collaborator is an active participant in the visualization process • Multiple, interlinked applications, where each collaborator runs their own application but data and parameter settings are programmed to be shared between the different applications ENV 2006

  33. Extends the dataflow model to interlink pipelines across the Internet Collaborative server provides the link So one user – for example - can send geometry to another person for viewing render internet Sharing the Visualization visualize data render share collaborative server share ENV 2006

  34. It is useful to be able to program the collaboration To adapt to how people want to collaborate To adapt to network bandwidths Here raw data is exchanged so a different visualization can be created visualise render internet Programming the Collaboration visualize data render share collaborative server share ENV 2006

  35. COVISA in action sharing isosurface level sharing data Collaborator B Collaborator A ENV 2006

  36. Multiple, Interlinked Applications • COVISA part of IRIS Explorer • Advantages • Great flexibility • Independent working • Disadvantages • Difficult to understand what the other user is doing ENV 2006

  37. Initiate collaborative session Scientist in lab Link in meteorologist remotely Bring in the Meteorologist Remotely ENV 2006

  38. We have studied many aspects of scientific visualization: Applications and history Different techniques for scalar and vector data Distributed and collaborative visualization The practical work is giving experience in Exploratory visualization (what is going on?) Presentational visualization (here’s what is going on!) Finally, this afternoon, two case studies Exploration using parallel coordinates Focus and context for volume visualization Conclusions ENV 2006

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