Focus and Context DIVA Research Group Master Seminar 2006/07 Lorenzo Clementi, 14/2/ of 13

Focus-and-context? Magellan Strait and the Terra Australis Incognita the in the map of Jodocus Hondius, of 13

Presentation outline ● Data representation, data presentation ● Distortion-based, non distortion-based presentations ● Some examples ● Detail-in-context ● Fisheye view, DOI function ● Fisheye menu: an example of fisheye view ● EPF and rubber sheet ● Conclusions 3 of 13

Data representation, data presentation Data representation: create an image representing some data. Data presentation: display on a physical support (screen) the data representation. 4 of 13

Non distortion-based and distortion-based presentations Non distortion-based: the whole data is provided at the same detail level. Distortion-based: a small amount of data is rendered in great detail, while the remaining data is displayed as context. The shading out from focus to context produces a distortion. 5 of 13

Detail-in-context Detail-in-context is a first step towards focus-and-context. Drawbacks: ● the magnified region leaks of context ● There is a discontinuity between the focus and the context 6 of 13

Focus-and-context: the idea 7 of 13 The focus region and its context are smoothly integrated in a single image

Fisheye view Fisheye view is the main focus-and-context technique. ● introduced by Furnas in 1986 (tree structures) ● it can be applied to many kind of data representation 8 of 13 ● a function selects the data that has to be displayed and computes its size of the resulting presentation

Fisheye view: DOI function The concept behind the fisheye view: Degree Of Interest (DOI) function The degree of interest depends on: ● the a priori importance of the item x ● its distance from the current point of focus y 9 of 13

Fisheye menu Fisheye views can be applied to many situations. Example: drop-down menu ● need to select an item from a long list ● the focus region is located where the mouse pointer is ● DOI function: sets the font size ● advantage: very effective for long lists ● drawback: it takes some time to be understood (ex. focus lock mode) ● demo demo 10 of 13

EPF framework Focus-and-context techniques require a common model to be compared and evaluated. Elastic Presentation Framework (EPF) ● 3D space, lens ● 3 major operations: ● Magnification ● Lens-style zooming ● Folding 11 of 13

Rubber sheet framework ● a rubber sheet is fixed on a rigid frame ● zooming corresponds to “stretching” ● the amount of stretching must be balanced by the same amount of “shrinking” ● stretching and shrinking are modelized by vectors 12 of 13

Conclusion ● Focus-and-context presentation methods are often ignored in commercial applications ● There exists very effective solutions that should be seriously considered when large amount of data has to be displayed ● Some of these solutions may require some time to be understood and some of them still need to be improved to be appreciated also by unspecialised users 13 of 13