Techniques for Interacting with Off-Screen Content Pourang Irani Carl Gutwin University of Manitoba University of Saskatchewan Grant Partridge Mahtab Nezhadasl University of Manitoba University of Manitoba Good afternoon. My name is Pourang Irani. I am presenting work I have done in collaboration with Carl Gutwin and our students Grant Partridge and Mahtab Nezhadasl.

Introduction R M R M R R R M R M R - It is very common to work with documents and workspaces that are larger than the user’s viewport. When we work with text documents, drawing applications or even simply viewing large images, we work with workspaces that span several viewports. With the rapid introduction of devices such as cell phone and PDAs, this is becoming very common. As a result a significant amount of information that is needed resides off-screen For instance, a common scenario could be that your friend asks you to meet her at a restaurant near the north gate metro station. To find this location the user has to start exploring various regions of the workspace. If the region is outside the viewing region then a certain amount of navigation may be necessary until the required information is located. In general, the issue relates to the idea of wanting access to some information, somewhere out of the viewable region or out of sight. Although techniques such as zooming and panning exist for browsing off-screen content, very little is known how they perform on a range of tasks We also want to know whether any one technique really works best for a range of different tasks R R R M R M R

2D navigation: Time Multiplexing Zooming R R M Time multiplexing techniques allow users to interact with different regions of the off-screen space at different times, in other words off-screen space is inspected in a serial fashion. There are a number of time-multiplexing techniques which include: scrolling, panning and zooming In the case of zooming, the user needs to move back and forth between different scales of the workspace in order to find the content of interest One potentially major drawback with time-multiplexing techniques is that \the user has to perform a significant amount of navigation to locate items of interest.

2D navigation: Space Multiplexing Overview+Detail DragMag R M R M Space multi-plexing techniques allow users to concurrently view different regions of the workspace at the expense of screen real estate. These include: O+D, Focus+Context and Portal based techniques. With techniques such as Overview + detail or DragMag there is the additional complexity in managing the overview and the detail windows.

Proxy-based techniques In these techniques, users interact with objects in the workspace through an intermediary proxy Proxy based techniques were introduced for inspecting remote objects or objects that are placed far form the user’s workspace The main ideas behind proxies is that they bring replicas of distant objects closer to the user’s interaction space, for further inspection This allows the user to see details of the target before performing the task, either targeting, or dropping In the case of drag-and-pop the user has to perform small hand movements to connect objects that are related, either for dropping objects onto others or for picking remote objects Vacuum is another technique designed by Bezerianos and Balakrishnan, that also relies on the idea of proxies for selecting remote content. [Bezerianos and Balakrishnan, 2005] [Baudisch et al., 2003]

2D navigation: Proxy Hop (Halo + Proxies) M R R R Hop is a proxy-based technique that allows the user to navigate to off-screen regions by first inspecting the targets. In Hop you have halos, with which you can interact to create proxies and then use the proxies to navigate off-screen. M R

Tasks Baudisch & Rosenholtz [2003] Spatially Absolute “Position” “Closest” “Avoid” Spatially Absolute Existence, Count, Location Spatially Relative Proximity to reference, Proximity b/w objects, Cluster We were interested in testing these various techniques not with only one task, but with a series of tasks. We began by categorizing these tasks. We started off with a set of tasks suggest by Baudisch & Rosenholtz, which they collected based on interviews with PDA users employing maps. These were “position”, “closest”, “avoid” We extended their set of tasks, into two abstract categories: Spatially absolute These describe the relationship between objects and the workspace Spatially relative These involve some form of relationship between different objects, and not b/w the objects and the workspace There are certainly many possible ways to categorize tasks, and many other tasks, such as traversing, route planning, etc. However we selected these as a starting point.

Evaluation: Conditions Navigation Techniques Zoom - two-level zoom DragMag Hop Tasks Absolute Relative We selected techniques to represent the different classes of systems. Zoom for time-multiplexing, DragMag for space-multiplexing, and Hop for proxy based. The experiment was performed on a 800x600 resolution with a TabletPC, so a pen-based device.

Zooming

DragMag

Hop

Results: Completion Time We found that users were twice as fast with Hop as DragMag or Zoom, on spatially absolute tasks. Participants also performed constantly the same with Hop on absolute tasks. However we noticed that participants performed better with Zoom than Hop or DragMag on spatially relative tasks. What is particularly interesting is that performance with DragMag always fell between these two extreme techniques on both types of tasks.

Possible explanations – strategy Number of operations about 1/5 with hop Zooming requires more “trips” … not so good for absolute tasks … but good for spatial information useful for relative tasks DragMag reduced the number of “trips” allows users to perform relative tasks with ease but added complexity of managing windows Hop was good with absolute tasks because it significantly reduction the amount of navigation necessary. This was primarily a result of using proxies. Zooming on the other hand required more “trips” but this was helpful with relative tasks but not so good for simpler absolute tasks. Primarily a result of different scales that does not disorient users. DragMag reduced the number of trips we observed with zoom but the added complexity made it cumbersome for absolute tasks. This was primarily a result of using different scales simultaneously.

Possible explanations – task-based Relative tasks Need orientation and comparisons b/w views Rely on VSTM Absolute tasks Require information about the objects Do not require spatial/orientation information

WinHop (hop + windows) We wanted to maintain the favourable properties of these different techniques and design hybrid systems. This led to the design of WinHop and MultiscaleZoom.

WinHop

WinHop

WinHop

WinHop

WinHop

WinHop (video)

MultiscaleZoom

MultiscaleZoom Take advantage of properties from Time-Multiplexing (zoom) and Proxy based

MultiscaleZoom (video)

Absolute: Location (winhop)

Relative: Cluster (msz)

Results MultiScale zooms outperforms the other techniques on both types of tasks. Interestingly performance is pretty much uniform with multi-scale zoom. Winhop comes in second, but primarily for the spatially absolute tasks. We see that for the Location task, Hop performs better than WinHop. This is primarily due to the fact that in hop users were teleporting but in WinHop they were using the window or portal. In Spatially relative tasks WinHop did not perform any better than Zoom, but significantly better than Hop.

Limitations of Hybrid Techniques WinHop Many operations, significant learning curve MultiScale Zoom Clutter from proxies

Main Findings Each task requires a different navigation strategy Proxy-based ideal for target-only info tasks Time/Space multiplexing ideal for target-target info Hybrids improve performance in both types of tasks Performance with Multiscale Zoom remained constant

Conclusion Beneficial to investigate techniques on multiple tasks Ideal technique gives target and context information Hybrid techniques are reliably good Consider multiscale zoom for small displays Hybrids performance on other tasks