The framework presented in this thesis is suitable also for the analysis of data from problem domains outside engineering. We have successfully used the same principles to analyze the evacuationof a building [74], asocial network[137], and ageospatial-temporaldata set [173].
Based on a collaboration with medical experts, the system has been adapted and improved to support the analysis ofmedical measurement datarecorded at the intensive care unit of a hospi-tal [160]. Another enhancement of the system has been used, in cooperation with ethologists, to analyze animals’ paths of motion in behavioral experiments [168].
8.5 Discussion
Sophisticated tools are required to explore and analyze complex, high-dimensional, and time-dependent data sets generated by the simulation of car components and subsystems. Computa-tional analysis methods have been widely used for such data sets. This thesis describes different, interactive visual analysis based approaches, which allow users to interact with the data and aid engineers in getting insight and generate useful knowledge from the raw numbers in a guided human-computer dialogue. We described a framework based on the concept of coordinated multiple views, specialized visualizations for time-dependent data, integrated computation of derived data attributes, and interaction techniques that support interactive data analysis. We also introduced novel 3D visualizations for multibody systems. The selection of tools and methods presented support common tasks, such as parameter sensitivity analysis and optimization. We discussed the benefits of those techniques and how engineers gain valuable insight into real-world simulation data using the proposed set of tools.
128 CHAPTER 8. SUMMARY
Chapter 9
Conclusions
“Everything‘s got a moral if only you can find it.”
— Lewis Carroll (1832–1898)1 Simulations of complex systems are routinely performed in several applications domains, in-cluding automotive engineering and meteorology. The simulation can be repeated with per-turbed input parameters to represent different boundary conditions or design choices. The goal of the analysts is to generate useful knowledge from the complex simulation results. Interactive visual analysis is seen as a valuable approach to assist them in this process [88]. Simulation results are multi-run, multivariate, and time-dependent. The analysis of this kind of data is particularly challenging, because analysis tools need to address all of those different data char-acteristics [118]. This thesis presented interactive visual tools and methods for the analysis of such complex data sets. Although our work is motivated by the need for the analysis of simu-lation results in the automotive industry, the discussed concepts are applicable to several other problem domains.
We use coordinated multiple views [214] to display different perspectives of the data. Novel visualizations for time-dependent data are integrated. A rich set of interaction possibilities en-ables the user to focus on interesting features. Focus+context visualization helps relate features to the rest of the data [59]. The focus can be iteratively changed, refined, or broadened, reflect-ing the user’s mental process durreflect-ing exploration. The rapid brushreflect-ing and studyreflect-ing of the linked views helps in the development of a mental model of the relations in the data. Correlations in multivariate results can be found, and relationships between features in parameter space and in result space can be explored.
We have integrated the on-demand computation of derived data attributes [61], such as ex-trema and first derivative of time-dependent data, into the visual analysis. This enables the ana-lyst to select also those features that cannot be specified via simple brushing of the original data variates. The combination of those building blocks allows the users to explore and analyze their data effectively. They can formulate and evaluate hypotheses visually to generate insight. They can use the insight gained to refine their hypotheses or generate new ones, making the process
1English author, mathematician, and logician. His most notable work isAlice’s Adventures in Wonderland.
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130 CHAPTER 9. CONCLUSIONS iterative. They can achieve complex analysis goals, such as exploring the system’s sensitivity to its parameters and finding optimal simulation parameter values. We also propose 3D visu-alizations to capture the spatio-temporal aspect of data generated by simulations of multibody dynamics.
Much of the work presented in this thesis was done while collaborating with engineers work-ing in automotive engine design. This collaboration was very inspirwork-ing, because we had a chance to understand what they want to achieve, what they expect from the visualization, and how they make sense of data. It was interesting to observe that engineers and the visualization commu-nity often have very different views on the analysis, even on basic terminology. Indeed, the two groups sometimes have markedly different concepts of “data”, “visualization”, and “analysis”.
We found that 3D visualizations were generally well-received. Engineers deemed them intuitive and they were able and willing to work productively with them. On the contrary, the more abstract visualizations integrated in coordinated multiple views were initially received with less enthusiasm. Interaction is crucial in working with such systems, and some of the engineers we collaborated with needed time to become able to leverage brushing and the coordination of views effectively (compare to Liu and Stasko [153]). Initially, they did not naturally engage in interactive exploration, but rather opted to use visualization only for confirmation. This is also reflected, to some extent, in their terminology, referring to visualization as “post-processing”, with little interaction implied. The flexibility in interaction that a general purpose system should offer is perhaps too much when the user focuses on more specific tasks. For visual analysis solutions targeted at specific tasks and domains, it may be more productive to streamline the interface for ease of use, also considering domain knowledge in the design [109].
In the traditional workflow, the analysis of simulation data begins after the simulation has finished and all data is available. Recently, there is an increased interest in real-time analysis and also real-time, interactive steering of simulations [210]. A challenge for future work is to incorporate new data into the analysis progressively as it is being generated, without causing the users to lose their overview and focus.
It is generally accepted in the visualization community that visualization for presentation requires very different values compared to visualization for exploration and analysis. Still, most of the engineers we worked with wished to use the same tools to analyze data and to document and present their findings. Considering their workflow, this requirement sounds natural. Never-theless, it is very difficult to provide tools that blend the interactivity, flexibility and performance required for exploration and analysis with the aesthetic values one expects in presentation. As a matter of fact, analysts often have to resort to using different, independent tools for the dif-ferent purposes, which hinders their workflow [223]. We speculate that the better integration of visual analysis systems with the tools used for presentation could lead to their more wide-spread acceptance.
Acknowledgments
“The only thing that will redeem mankind is cooperation.”
— Bertrand Russell (1872–1970)1 Completing this thesis would not have been possible without the support and cooperation from a lot people. First and foremost, I would like to thank my supervisorHelwig Hauser(now with the University of Bergen, formerly with the VRVis Research Center) for his support. He was always there to point out the most interesting directions of work and also to provide the most valuable constructive comments and feedback, exactly at the right time. Very special thanks go toKreˇsimir Matkovi´c(VRVis) for the immense professional and moral support. Thank you for steadily encouraging me to continue working on and eventually finishing this thesis.
This thesis was written while working for theVRVis Research Center(www.vrvis.at) and collaborating withAVL-List GmbH(www.avl.com), active in internal combustion engine research and development. AVL’s contribution goes far beyond providing data sets for testing and demonstrating ideas. People at AVL contributed in many different ways to this thesis. They identified open issues and problems in their everyday work where interesting opportunities for interactive visual analysis could be found. Their input as domain experts is invaluable. I am thankful to my coauthors at AVL, in alphabetical order: Mario Duras, Mario Jelovi´c, Josip Juri´c, andJ¨urgen Krasser, as well asAlan Leˇzat VRVis. Furthermore, the long and fruitful dis-cussions withSaˇsa Bukovnik,Wolfgang Hellinger,Bernhard Loibnegger,G¨unter Offner,Martin Sopouch, andChristian Vockat AVL have made me more aware of the engineering background, which inevitably also made me understand the visualization and visual analysis problem better.
Additional thanks go toAudrey Cahill(AVL),Mark A. Mitterdorfer(now with Intel Corporation, formerly with AVL),Robert S. Laramee(now with Swansea University, formerly with VRVis), Johannes Tax, andMichaela Hallerfor their feedback on my papers. I am also grateful to the anonymous reviewers for their constructive comments.
I am particularly thankful toDenis Graˇcanin(Virginia Tech) for the perfectly timed collab-orations on papers and for using the time zone difference between Austria and the United States to our maximum advantage. He really knows how to make that productive. Special thanks go to Meister Eduard Gr¨ollerandWerner Purgathofer(Vienna University of Technology) for turning seemingly big problems into non-problems. This thesis could not have been finished without their support. I am grateful toL´aszl´o Szirmay-Kalos(Budapest University of Technology), the
1British philosopher, logician, mathematician, and social critic. Received the 1950 Nobel Prize in Literature in recognition of his varied and significant writings in which he champions humanitarian ideals and freedom of thought.
131
132 ACKNOWLEDGMENTS supervisor of my master’s thesis. I have always been interested in computer graphics since I was about 12, but he was the one who encouraged me to write my first conference paper and started me out on the path of computer graphics research. After so many years, thank you.
Finally, but most importantly, thanks go to my lovely wifeEditwho supported and encour-aged me during the long days and nights before submitting papers and endured my occasional ramblings about visual analysis at home. Very special thanks and warm hugs to my daughters AnnaandJulia, who missed Daddy so much while he was working on this thesis. I appreciate the sacrifices they made.
Curriculum Vitae
About Zolt´an Konyha
Zolt´an Konyha, MSc, born on 27 December 1976, in Gy˝or, Hungary, as the first son of Dipl.-Ing.
M´arta Csiff´ary and Dipl. Ing.-L´aszl´o Konyha.
Married with Edit Csap´o, MSc.
Two daughters, Anna (2006) and J´ulia (2011).
Contact information
Address: Lilienthalgasse 39, A-8080 Graz, Austria. Email:konyha@vrvis.at
Education
1991–1995 R´evai Mikl´os Gimn´azium(high school) in Gy˝or, Hungary. Graduation (Matura) with highest distinction in June 1995.
1995–2001 Studies of Computer Scienceat the Budapest University of Technology and Eco-nomics, focus on Business Telecommunication and Computer Aided Design of Information Systems.
2001 Diploma thesis: Automobile Simulation in Virtual Environment (in Hungarian).
Supervisor: Dr. L´aszl´o Szirmay-Kalos. Graduation to “Master of Science in Technical Informatics”.
2006– Phd studentin Computer Science (Informatik) at the Vienna University of Tech-nology, resulting in work on thisPhd thesisat the VRVis Research Center.
Professional activities
1998–1999 Teaching assistant, lab on the Unix operating system, at the Dennis Gabor Col-lege, Budapest, Hungary. (ref: Dr. P´al Jedlovszky)
2001–2012 Junior Researcherand Software Developer at VRVis Research Center, Vienna, Austria. (ref: Dipl.-Ing. Georg Stonawski)
2012– Software Engineerat AVL-List GmbH, Graz, Austria. (ref: Dr. J¨urgen Krasser) 133
134 CURRICULUM VITAE
Activities related to scientific work
• Research projectSimulation and analysis of TCP traffic over ATM telecommunication networks with Ericsson Research Hungary in 1998 during my studies at the Budapest University of Technology and Economics. (ref: Dr. Gergely Seres, Ericsson Research Hungary)
• Diploma thesis: Automobile Simulation in Virtual Environment (in Hungarian) at the Department of Control Engineering and Information Technology, Budapest University of Technology and Economics. Supervisor: Dr. L´aszl´o Szirmay-Kalos. (January 2001)
• Reviewer for conferences: Advanced Visual Interfaces (2010), Eurographics / IEEE Symposium on Visualization(2009-2010),Spring Conference on Computer Graphics(2010), Winter School of Computer Graphics(2010),
• Co-authorof the “Simple and Effective Integrated Display”award winning entry[173]
to theVAST Challenge 2008(a participation category of theIEEE VAST 2008 Symposium, part ofVisWeek 2008).
Publications
Please see theRelated Publications and theBibliographysections of this thesis for a list of publications related to the contents of this thesis.
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