Smart Visibility in Visualization
3. Exploded Views and Deformations
Exploded views and deformations modify the spatial ar-rangement of features to uncover the most prominent ones.
It is also a very effective way to present assembly in-structions. Exploded views enable a clear view on indi-vidual features and convey the information about the orig-inal spatial location by helpers such as lines or arrows.
Agrawala et al. [APH∗03] proposed design principles for creating effective assembly instructions based on exploded views. They additionally present a system for the auto-matic design of assembly instructions and a system that semi-automatically generates exploded views from two-dimensional images [LAS04]. The rules for assembly in-structions are based on cognitive psychology and experi-ments:
• assembling is decomposed into a hierarchy of operations and parts
• parts in the same hierarchy (e.g., legs of a chair) have to be added at the same time-step, or in sequence one after another
• step-by-step instructions are better understandable than a single diagram showing all the operations
• diagrams presenting the final assembly are necessary to understand the step-by-step action diagrams
• parts added in the current assembly step must be clearly visible
• objects have to be presented in their clearest orientation Smart-visibility visualizations are using some of the above mentioned rules for other tasks than assembly in-structions. In the following visualization approaches are pre-sented that have been inspired by the exploded views con-cept. They use some of the rules for assembly instructions implicitly.
3.1. Applications in Visualization
One of the visualization techniques that is closely related to exploded views is volume splitting [IDSC04,GBKG04].
This technique is intended for displaying multiple enclosed iso-surfaces within the volumetric data. Each iso-surface, ex-cept the innermost one, is split into two parts and moved apart. Such splitting is denoted as logical splitting. Another type is geometrical splitting which moves apart the two halves of the entire volume. Logical splitting is illustrated in Figure1(b).
McGuffin et al. [MTB03] propose an elaborate frame-work featuring a set of advanced deformations for an under-standable visual presentation of complex three-dimensional information. The operation for investigating the interior of a volume is browsing. The browsing is realized on pre-segmented data decomposed into several semantic layers (e.g., skin, muscle, skull, brain). The user can cut into and open up, spread apart, or peel away parts of the volume in real time. This makes the interior visible while still retain-ing surroundretain-ing context. Additionally they present a set of interaction techniques based on various metaphors. Interac-tion techniques are controlled by pop-up menus and three-dimensional widgets. The interaction technique using leaf-ing deformation is shown in Figure1(c).
Another interesting visualization technique inspired by exploded views is called fanning in time [GBKG04]. This technique is different from previously mentioned tech-niques, because it is a temporal exploded view analogous to temporal exploded views and multiple exposure pho-tographs. It is useful for the visualization of time-series with a relatively small number of time-steps. The main goal is to show all time-steps in one image similar to illustrative pho-tographs of a skateboarder performing a certain skateboard trick. Figure9illustrates the idea of fanning in time and the correspondence to illustrative photography.
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The Eurographics Association 2005.
Viola and Gröller / Smart Visibility in Visualization
Figure 9: Illustrative photography of a skateboarder per-forming a jump (top). Photography expressively displays the principle of a particular trick. The photography is courtesy of Trasher magazine. Fanning in time (bottom) shows all time steps of time-varying dataset of beating heard [GBKG04].
4. Conclusions
In this part of the tutorial we have presented expressive vi-sualization techniques inspired by strategies from traditional illustration. We have shown that many challenging visual-ization tasks can be solved by adopting existing techniques from visual arts. Although computer generated visualization can hardly compete hand crafted illustrations in terms of ex-pressivity, harmony, or esthetics, considerable advantage to traditional illustration is the aspect of real-time interaction and manipulation. Effective combination of expressive visu-alization techniques with right interaction tools conveys the information on complex scientific data much better than a static image.
5. Acknowledgements
The work presented in this publication is car-ried out as part of the exvisation project (www.cg.tuwien.ac.at/research/vis/exvisation) supported by the Austrian Science Fund (FWF) grant no.
P18322.
References
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[BG05] BRUCKNERS., GRÖLLERM. E.:VolumeShop:
An Interactive System for Direct Volume Il-lustration. Tech. rep., Institute of Computer Graphics and Algorithms, Vienna University of Technology, 2005. 4
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[DWE03] DIEPSTRATENJ., WEISKOPFD., ERTLT.: In-teractive cutaway illustrations. InProcceedings of Eurographics’03(2003), pp. 523–532. 2 [FS92] FEINERS., SELIGMANN D.: Cutaways and
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[GMS∗02] GIESECKEF., MITCHELL A., SPENCER H., HILL I., DYGDONJ., NOVAK J.: Technical Drawing. Prentice Hall, 2002. 2
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M.: Spatial and temporal splitting of scalar fields in volume graphics. In Proceedings of IEEE/SIGGRAPH Symposium on Volume Visu-alization’04(2004), pp. pp. 87–94. 1,5 [LAS04] LI W., AGRAWALAM., SALESIN D.:
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Smart Visibility in Visualization I. Viola and M. M. E. Gröller
Institute of Computer Graphics and Algorithms Vienna University of Technology
I. Viola and M. E. Gröller 1
Smart Visibility Techniques
Artificial modifications of the data to enhance visibility of important features
Expressive illustration techniques Visual modifications
Section views
Cut-away and ghosted views Spatial deformations
Deformations Exploded views
I. Viola and M. E. Gröller 2
Motivation
I. Viola and M. E. Gröller 3
Section, Cut-Away, Ghosted Illustrations
http://www.medigraphics.com/
http://www.khulsey.com/
Rules for Cut-Aways and Section Views
Inside and outside objects are differentiable Section view is intersection of two half spaces Section view is aligned to main axis of outside object Jittering mechanism is useful for cut-outs
Mechanism to make the walls visible is needed Cut-away views are single hole in outside object Interior objects are visible from any viewing angle [Diepstraten et al. ’03]
Additional Rules for Ghosted Views
Transparent objects never shine through
Opaque objects occluded by two transparent objects do not shine through
Transparency falls-off close to the edges of transparent objects
[Diepstraten et al. ’02]
I. Viola and M. E. Gröller 6
Viewpoint Independent Cut-Away Views
[Löffelmann et al. ‘97] [Pflesser et al. ‘02]
Streamarrows Volume Cutting
I. Viola and M. E. Gröller 7
Viewpoint–Dependent Cut-Away Views
[Straka et al. ’04] [Bruckner et al. ’05]
VesselGlyph ICPVR VolumeShop
I. Viola and M. E. Gröller 8
representation
0 importance max
dense
Importance-Driven Feature Enhancement
importance importance specification
specification levels of levels of sparseness sparseness importance
importance compositing compositing
0.1
0.7 0.10.7
importance-driven feature enhancement [Viola et al. ’04 ‘05]
importance importance specification
specification levels of levels of sparseness sparseness
0.1
0.7 0.10.7
representation
0 importance max
dense
importance importance compositing compositing
I. Viola and M. E. Gröller 9
Applications
I. Viola and M. E. Gröller 10
Deformations and Exploded Views
http://www.medigraphics.com/
http://www.khulsey.com/
I. Viola and M. E. Gröller 11
Deformations
[Carpendale et al. ‘96] [Mackinlay et al. ‘99]
I. Viola and M. E. Gröller 12
Browsing Deformations
[McGuffin et al. ’03]
Leafer
Peeler
I. Viola and M. E. Gröller 13
Spatial Exploding
[Islam et al. ’04]
Volume Splitting
[Grimm et al. ’04]
Dynamic Multi-Volumes
I. Viola and M. E. Gröller 14
Temporal Exploding (C.E.M.E.N.T. )
I. Viola and M. E. Gröller 15
Temporal Exploding
[Grimm et al. ’04]
Fanning in Time
Conclusions
Visual arts are source of inspiration Illustrations are nicer than synthetic image Visualization can be interactive, illustration not Smart visibility makes visualization expressive
Local modification of visual properties Modification in spatial arrangement
Thank you!
Questions???
viola@cg.tuwien.ac.at