HUMAN-COMPUTER INTERACTION
SECOND EDITION
HUMAN-COMPUTER INTERACTION
SECOND EDITION
Gesture is a component of human-computer interaction that has become the subject of attention in multi-modal systems. Being able to control the computer with certain movements of the hand would be advantageous in many situations where there is no possibility of typing, or when other senses are fully occupied. For some disabled users, such as the deaf, it offers a mode of communication that is familiar. But, like speech and handwriting, gesture is user dependent, subject to variation and co-articulation. The technology for capturing gestures is expensive; either a vision system (see below) or a dataglove (see Chapter 2) is needed. The dataglove provides easier access to highly accurate information, but is a relatively intrusive technology, requiring the user to wear the special Lycra glove. The interpretation of the sampled data is very difficult, since segmenting the gestures causes problems. A team from Toronto [88] have produced a gesture recognition system that translates hand movements into synthesized speech, using five neural networks working in parallel to learn and then interpret different parts of the inputs.
Granularity of integration What is the appropriate level of integration between different streams of information? Should every action be linked to an audio or video stream at the instant that action was performed, or does it make more sense to use a coarser level of granularity?
Supporting revision during access It is important to integrate different streams of information at the time they are originally captured. For example, in a classroom setting, it makes sense to link what an instructor says with what she is writing or showing at that time in class. From a student's perspective, however, it may be equally important to provide the capability to modify a record of a class after the class as well. It therefore becomes important to consider capture and integration activities that occur during the access phase.
Virtual reality (VR) refers to the computer-generated simulation of a world, or a subset of it, in which the user is immersed. It represents the state of the art in multi-media systems, but concentrates on the visual senses. VR allows the user to experience situations that are too dangerous or expensive to enter 'in the flesh'. Users may explore the real world at a different scale and with hidden features made visible. Alternatively, the virtual worlds that are generated may be entirely synthesized: realistic within themselves, but purely a manifestation of electronic structures.
A stronger sense of connection can be obtained using semi-transparent goggles. Users can move around in the real world and see real objects, but computer images are reflected off the inside of the glass and overlay the physical objects. Again this can be used to show unrelated information; for example, some wearable computers allow users to read their email whilst walking around. However, the real sense of two worlds meeting comes when the projected image in some way links or refers to the object it overlays. For example, one experimental system has virtual balls, which can be picked up and thrown by the user [8]. When the virtual ball 'hits' the real wall it bounces off. The balls can even bounce down a real staircase.
VR and 3D displays can be used to visualize scientific data and other complex information. Whether or not 3D representations are used, animation techniques, especially when under interactive user control, can give a sense of engagement with data, and encourage discovery and pattern formation.
Perhaps the most powerful use of time is when changes are under user control - interactivity. This is central even to our perception of three dimensions. Stereo vision, shadows and lighting all give an impression of depth, but it is the ability to move around an object, to view it at different angles, which gives a true sense of a real 3D object. Interactivity is also a key factor in the virtual wind tunnel. A movie of the wind tunnel would be useful, but the real power comes because the engineer can move about inside the tunnel, using bubble tracers to investigate particular areas of interest. Another example of the use of interaction is the interface in Figure 15.13 for viewing the Visible Human [182]. A slider is used to control the position of the viewed slice in the body. In this case the slider corresponds to spatial dimension. In other systems sliders are used to select values or ranges for parameters. One system, Homefinder, uses max-min sliders to select price ranges, number of rooms, etc., while in real time a map shows the locations of all houses satisfying the criteria. Even more complex data are visualized using the Influence Explorer [244], which shows the results of a multi-parameter/multiple result mathematical model. The user selects parameter/performance ranges and in real time a histogram displays the number of simulations that satisfy all or most of the criteria (Figure 15.14). Colour is used to represent full vs. partial matches.
Disabled users may find systems that take full advantage of their capabilities so that their disability is minimized and not highlighted, whereas able-bodied people might find that interaction becomes natural, fun, efficient and effortless. We may all benefit from these newer interaction styles that utilize more of our senses in an involving interactive experience, but only if this is wisely done.
A classic paper which not only showed that virtual reality could be available at a much lower cost than previously assumed, but also exposing the critical factors for a sense of engagement.
Non-cursor process indicators often take the form of a pop-up box with a moving slider, or a stick person walking backwards and forwards. These are important to give the user a sense of progress and to prevent inactivity being interpreted as an indication of a system fault. In addition, animated icons may be used to show system state; for example, Netscape Navigator has shooting stars to indicate that it is downloading information. Animated icons can also be used to make the meaning of the icon clearer. This is especially useful for icons representing actions that are not well represented by static image. However, such animation must be used sparingly to avoid distraction!
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