Panel Organizer and Moderator: Dirk Bartz, University of Tübingen. Panelists: Hans Hagen, Technical University of Kaiserlautern. Victoria Interrante, University ...
Illustrative Rendering Techniques for Visualization: Future of Visualization or Just Another Technique? Panel Organizer and Moderator: Dirk Bartz, University of T¨ ubingen Panelists: Hans Hagen, Technical University of Kaiserlautern Victoria Interrante, University of Minnesota Kwan-Liu Ma, University of California, Davis Bernhard Preim, University of Magdeburg
Figure 1: Illustrative rendering of anatomical and technical objects. From Left to right: Abdominal dataset with colon, skeleton and skin; skull; CT scan of ignition plug of motor; head with skull and paranasal sinus. Images are courtesy of Zein Salah, VCM, University of T¨ ubingen.
I NTRODUCTION Illustrative rendering has gone a long way already. While it has been a topic at Eurographics, ACM SIGGRAPH, and other events since the early nineties, it was basically introduced to visualization by Interrante et al. in 1996 [2], and later by Treavett/Chen [3] and by Ebert/Rheingans [1]. At last years IEEE Visualization conference, illustrative rendering for visualization has been identified as one of the items on the agenda of future research items. Furthermore, it has been chosen next to perception and other topics as one of the special topic areas for IEEE Visualization 2005. Illustrative rendering, often also depicted as non-photorealistic rendering1 or stylized rendering, employs abstraction techniques to convey the relevant information, and de-emphasize less important details. The question remains how this abstraction process is guided and in particular how can we ensure that relevant information is maintained. Consequently, research on illustrative rendering needs to address how the information is perceived by the human observer, next to the investigation of algorithmic aspects. In this panel, we will discuss various aspects on this topic. Kwan-Liu Ma will discuss how illustrative rendering can be used 1 This term seems to be inappropriate to differentiate illustrative rendering from “traditional” visualization, since visualization is typically not photorealistic.
IEEE Visualization 2005 October 23-28, Minneapolis, MN, USA 0-7803-9462-3/05/$20.00 ©2005 IEEE.
in scientific visualization, and Bernhard Preim will explore its use for the visualization in the medical imaging domain. Perception aspects will be presented by Victoria Interrante. A different perspective if illustrative rendering is useful for typical visualization problems will be added by Hans Hagen. M ODERATOR ’ S AND PANELISTS ’ S S TATEMENTS AND B IOGRAPHIES Dirk Bartz: Is illustrative rendering focusing on important features, or does remove important details? Position Statement As pointed-out above, illustrative rendering techniques have been chosen as one important items on the list of current research topics. While there are several examples how illustrative rendering can be used to add valuable insights to a variety of different datasets, it overall merits for visualization are not (yet) clear. Is it able to routinely deliver more than beautiful images? Do the used abstraction techniques guide the user to the important data features? How difficult is the parametrization of the techniques to achieve the goals? I think that this has not been sufficiently answered so far. In this panel, we hope address these questions from various perspective. Biography Dirk Bartz is head of the research group on Visual Computing for Medicine (VCM), a jointed research group of the Computer Graphics Laboratory (WSI/GRIS) of the University of Tu¨ bingen and of the University Hospital T¨ubingen. His recent works covers interactive virtual medicine, illustrative rendering, and stylized augmented reality. In 1998, he was co-chair of the ”9th Eurographics Workshop on Visualization in Scientific Computing” and in 2002 he was
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Professor Ma received his PhD in computer science from the University of Utah in 1993. During 1993-1999, he was with ICASE/NASA LaRC as a research scientist. In 1999, he joined UC Davis. In the following year, Professor Ma received the Presidential Early Career Award for Scientists and Engineers (PECASE) for his work in parallel visualization. In 2001, he received the Schlumberger Foundation Technical Award for his work in large data visualization. Professor Ma is a member of IDAV (Institute for Data Analysis and Visualization). Currently, he is leading research projects in parallel rendering, volume modeling and visualization, artistically inspired illustrations, visual interface designs, and information visualization. He organized a SIGGRAPH 2002 course on NPR. He is presently organizing a NSF sponsored workshop on cyber security, and also serves on the program committees of the Visualization 2005 Conference as well as the Information Visualization 2005 Symposium. He is the editor of the VisFiles Column of the ACM SIGGRAPH’s Computer Graphics Quarterly. Bernhard Preim: Find out where illustrative techniques provide a real benefit Position Statement
Figure 2: Illustrative rendering of abdominal dataset, frontal view with colon (red), skeleton (blue), and skin (pink). Image is courtesy of Zein Salah, VCM, University of T¨ ubingen.
chair of the ”4th Eurographics Workshop on Parallel Graphics and Visualization”. Dirk studied computer science and medicine at the University of Erlangen-N¨urnberg and at Stony Brook University. He received a Diploma (M.S.) in computer science from the University of Erlangen-N¨urnberg, and a Ph.D. in computer science from the University of T¨ubingen (both in Germany). Kwan-Liu Ma: User’s knowledge needs to be incorporated Position Statement While volume rendering technology has become mature, competent illustrative rendering techniques for visualization are still lacking. Some researchers in the visualization field, including myself, have been working on new and improved non-photorealistic rendering (NPR) techniques. However, illustrative rendering encompasses far more than just rendering, including such topics as interface support and the ability to incorporate domain knowledge. The rendering component of illustrative rendering has seen steady progress, but the other two components have not kept pace. We have seen silhouette rendering of a CT engine scan, stippled rendering of an MRI-based human head scan, and tone shading of a jet stream simulation. But these images are not necessarily illustrative to the scientists producing the data, and may not even be as valuable as traditional direct volume rendering. Before truly illustrative rendering is practical, we must understand how to incorporate the knowledge and to answer the questions of those directly involved with the data. Biography Professor Ma’s research spans the fields of visualization, computer graphics, and high performance computing. His goal is to continuously advance the state of the art in data visualization technology.
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Illustrative rendering techniques are an essential extension to conventional rendering techniques which have a great potential in clinical applications, such as diagnosis and therapy planning. To be accepted by physicians, illustrative techniques need to be combined with conventional medical visualization techniques. The use of illustration techniques must not hamper interactivity. Therefore, efficient and frame-coherent techniques are urgently needed. We explored efficient cylindrical cut-away views to emphasize and investigate small pathologies. Illustrative techniques allow to emphasize important regions, such as those around a pathology, and to integrate more information in one visualization, for example functional and anatomic information. Two informal studies we conducted for for Ear-, Noseand Throat surgery and liver surgery planning revealed that silhouette and feature lines are regarded as useful to depict large objects serving as anatomic context (see Fig. 3). Illustrative techniques such as hatching often require additional preprocessing such as sophisticated smoothing and/or the adjustment of many parameters which is tedious and may lead to suboptimal results. Due to the severe time constraints in clinical settings, the use of illustrative rendering techniques must be carefully finetuned to particular visualization problems and clinical tasks. Presets are required in order to provide good “suggestions” for the parameters of illustrative rendering techniques. We should carefully fine-tune our illustrative techniques to particular clinical problems; otherwise they never get used in clinical settings. We also need to demonstrate an advantage in controlled user studies. We should find out in which specific situations illustrative techniques have a benefit and are more than just a nice feature. Biography Bernhard Preim received the diploma in computer science in 1994 (minor in mathematics) and a Ph.D. in 1998 from the Otto-vonGuericke University of Magdeburg. He then moved to Bremen where he joined the staff of MeVis (Center for Medical Diagnosis System and Visualization). In close collaboration with radiologists and surgeons he directed the work on ”computer-aided planning in liver surgery” and initiated several projects funded by the German Research Council in the area of computer-aided surgery. In June 2002 he received the Habilitation degree (venia legendi) for computer science from the University of Bremen. Since Mars 2003 he
Biography Victoria Interrante is an Associate Professor in the Department of Computer Science and Engineering at the University of Minnesota, where she has taught since 1998. Her research focuses on the application of insights from visual perception, art and illustration to the design of more effective techniques for conveying information through images. Dr. Interrante received her PhD in 1996 from the University of North Carolina at Chapel Hill, and worked from 1996-1998 as a staff scientist at ICASE, a non-profit research center operated by the Universities Space Research Association at NASA Langley. In 1999 she received a Presidential Early Career Award for Scientists and Engineers for her research in seeking insights into the science behind the art of effective visual representation. Hans Hagen: Immerse the user - integrate him/her in the visualization environment Position Statement
Figure 3: Visualization for Neck Dissection planning. Anatomic context visualized as combination of strongly transparent surface and silhouette rendering. Image is courtesy of Christian Tietjen, University of Magdeburg.
is full professor for ”Visualization” at the computer science department at the Otto-von-Guericke-University of Magdeburg, heading a research group which is focused on medical visualization and applications in surgical education and surgery planning. Bernhard Preim is member of the ACM and the German Chapter of the ACM where he served as Vice-President (2001-03) and Past Vice- President (2003- 05). He is speaker of the working group Medical Visualization in the German Society for Computer Science. He is member of the scientific advisory boards of ICCAS (International Competence Center on Computer-Assisted Surgery, since 2003) and CURAC (German Society for Computer- and Roboter-assisted Surgery, since 2004) and Visiting Professor at the University of Bremen. Victoria Interrante: Applying insights from perception to the development of effective illustrative renderings Position Statement The ultimate goal of using illustrative rendering in visualization is to improve a viewer’s ability to perceive important, task-relevant information about a represented dataset by displaying it in a nonphotorealistic manner that selectively emphasizes the most critical features in the data while concurrently minimizing the visual salience of unimportant and potentially distracting details. The key challenges in developing an effective illustrative rendering are: to determine what the important features are of the data that the viewer needs to understand, and to determine how to represent these features in a way that facilitates his efforts to achieve the desired understanding. In my panel statement I will review some of the fundamental insights that we can draw from historical research in visual perception to help guide the design of effective illustrative representations.
Common approaches to visualization largely consist of stressing the points in which computers exceed human performance. They are based on the assumption that users working with a visualization system will have to adapt themselves to their working environment and not vice versa. These approaches do not sufficiently take into account that computers may be very efficient at fast searching and ordering large amounts of data, while humans are much more adept at visually arranging and manipulating data, as well as recognizing relations between different sets of data (meta-data). The logical conclusion is that illustrative rendering techniques should emphasize the strengths of both humans and machines in an immersive visualization environment, in order to achieve great improvements in the effectiveness of common workflows. Therefore, illustrative rendering methods must present and visualize data in a way that integrates the user into his artificial surroundings seamlessly and give him/her the opportunity to interact with it in a natural way. The research in illustrative rendering should not only take into account visualization techniques but should also include new ways for interacting with the data and the provided visualizations. In addition, the user should be supported by self-adapting techniques (regarding the used hardware and software environment, the data itself, the user’s demands and knowledge, etc.) - for me, a smooth integration of illustrative rendering and artificial intelligence methods seems to be one key element for such approaches. Biography Hans Hagen received his PhD in Mathematics from the University of Dortmund in 1982. From 1983 to 1986 he covered a position as Assistant Professor at the Arizona State University. In 1986 he was appointed full professor at the Technical University of Braunschweig. Since 1988 Hans Hagen is a full professor for Computer Science at the University of Kaiserslautern. There, he is heading the research group for Computer Graphics and Computer Geometry. In addition to his position at the university, in 1998 he joined the German Research Center for Artificial Intelligence (DFKI). At this institute he covers the position of a Scientific Director and Head of the research lab Intelligent Visualization and Simulation. Besides his duties as Professor and Head of research lab, he serves the University of Kaiserslautern as Dean of the Computer Science Department and as member of the University’s Advisory Board. Hans Hagen is both national and international a pioneer in his research domains geometric modeling and scientific visualization. Additionally, his scientific interests cover the domains of computer graphics and computer aided geometric design. He is the former Editor-in-Chief of the IEEE Transactions on Visualization and Computer Graphics and is co-editor of all relevant computer
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graphics journals. His scientific work covers more than 150 refereed publications and 14 books. He received a number of awards: John Gregory Memorial Award for Research Accomplishments in Geometric Modeling (2001), IEEE Computer Society Meritorious Service Award (2002), and IEEE Computer Society Golden Core Membership (2004). Since January 2005 he is also PI of the International Research Training Group “Visualization of Large and Unstructured Data Sets”. R EFERENCES [1] D. Ebert and P. Rheingans. Volume Illustration: Non-Photorealistic Rendering of Volume Models. In Proc. of IEEE Visualization, pages 195–202, 2000. [2] V. Interrante, H. Fuchs, and S. Pizer. Illustrating Transparent Surfaces with Curvature-Directed Strokes. In Proc. of IEEE Visualization, pages 221–218, 1996. [3] S. Treavett and M. Chen. Pen-and-Ink Rendering in Volume Visualization. In Proc. of IEEE Visualization, pages 203–210, 2000.
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