HUMAN-COMPUTER INTERACTION
SECOND EDITION
HUMAN-COMPUTER INTERACTION
SECOND EDITION
We have seen several groupware systems which attempt to compensate for these losses. In Section 13.4.2, we discussed the idea of a group pointer, a mouse-controlled icon which can be used to point to things on a shared screen. Somewhat more esoteric, but more immediate, are the shared work surfaces (Section 13.4.3) which mix an image of the participants' hands with the electronic screen. The participants can then simply point at the relevant item on the screen, as they would face to face.
When recordings are replayed, they can be digitally speeded up. If you simply play an audio recording faster the pitch rises - human speech ends up rather like Mickey Mouse's. However, digital signal-processing techniques can accelerate a recording while keeping the same pitch. Speech can be played back at up to twice the normal rate without any loss of comprehensibility. This can be used in a
Users with physical disabilities vary in the amount of control and movement that they have over their hands, but many find the precision required in mouse control difficult. Speech input and output is an option for those without speech difficulties.
VR has been made possible by the advent of very fast high-performance computers. Despite the exponential rise in processor speeds, high-resolution immersive VR is still not available for mass-market applications, and many systems are primarily research projects. Desktop VR is a lower-cost alternative. In desktop VR, 3D images are presented on a normal computer screen and manipulated using mouse and keyboard, rather than using goggles and datagloves. Many readers may have used such systems on personal computers or games consoles: flight simulators, or interactive games such as DOOM or MYST.
This form of VR has become available to many through VRML (Virtual Reality Markup Language), which allows virtual worlds to be distributed over the Web and integrated with other Web-based materials (Figure 15.7). VRML worlds can include static 3D objects, which the user can navigate around looking at different aspects, and dynamic objects that move about and react when 'touched' by the mouse cursor. In addition, VRML is integrated with the rest of the Web by link objects, which, when clicked, take you to another web page or VRML world. Other Internet-based VR systems are also available that allow greater interactivity and collaboration with other remote users (see also Chapter 13).
There are many different ways of traversing the network, and so there are many different ways of reading a hypertext document - the intention is that the user is able to read it in the way that suits him best. Links can exist at the end of pages, with the user choosing which one to follow, or can be embedded within the document itself. For example, in an on-line manual, all the technical words may be linked directly to their definitions in the glossary. Simply clicking on an unknown word takes the user to the relevant place in the glossary. Another unknown word encountered there can also be traced back to its definition and then the user can easily return to his original place in the manual. The positions of these links are known as hot-spots since they respond to mouse clicks. Hot-spots can also be embedded within diagrams, pictures or maps, allowing the user to focus his attention on aspects that interest him.
The popularity of the Web is due mainly to the ease of use offered by the browsers, notably Mosaic, Netscape Navigator and Microsoft Internet Explorer. These offer a graphical interface to the document, controlled by the mouse. Hypertext links are shown by highlighting the text that acts as the link in an alternative colour and are activated by clicking on them. A further colour is used to indicate a link that has already been visited. Hypertext links can also be embedded into regions within an image. The browser contains most of the functionality required to view a web document, supporting text and graphics in an integrated package. Movies are less well combined, requiring a separate viewing package to be spawned, such as a
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