HUMAN-COMPUTER INTERACTION
SECOND EDITION
HUMAN-COMPUTER INTERACTION
SECOND EDITION
In many command and control situations, real users are at one remove from the physical world, seeing it through windows, or cameras. The windows or video screens can be replaced by synthesized pictures. The user operates within an immediate physical environment, with real controls and instruments, but the world outside is virtual.
One such interactive VR application in widespread use is the flight simulator. A full cockpit system is placed in a hydraulically supported container, with large screens replacing the cockpit windows. Images are generated and projected onto the screens, whilst the box can be moved rapidly in any direction by the hydraulic rams. The visual information and physical motion simulate accurately the conditions encountered by aircraft. Flight simulators are used extensively in pilot training programmes. Landings can be practised, with the system responding to the commands of the pilot; descending too fast and off to one side, the pilot will have to correct the situation if she wishes to avoid a crash. Emergency situations can also be created, in which aircraft system malfunctions can be artificially created in order to train the pilot to take the correct course of corrective or life-preserving action. With VR, entertainment is never far behind and this kind of system can also be found in many fun fairs!
The advent of ever-faster processors has meant that the graphical capabilities of computer systems have become much better since the early 1990s, allowing more complex displays to be drawn. The ability to draw thousands of lines on the screen every second has meant that the range of possibilities for presenting information has been extended. One effect of this is that animation has become a more common element in systems. Animation is the term given to the addition of motion to images, making them move, alter and change in time. A simple example of animation in an interface is in the form of a clock. Digital clocks can flick by the seconds, whilst others imitate Salvador Dali and bend and warp one numeral into the next. Analog clocks have moving hour and minute hands, with an optional second hand sweeping round the clock face. Such a desktop accessory is found in a lot of interface setups, and the additional processing time required to produce such effects is no longer a major factor.
Another common use for animation in current windowing systems is to animate the cursor. Instead of simply having a basic pointer always on the screen, many interfaces now use the typical 16 ¥ 16 bitmap that makes up the cursor to indicate more complex information. We have seen in Chapter 3 that there are a number of different static cursors that are used, but animation takes this one stage further by adding motion to the images. This is usually done to indicate that some process is in progress, to confirm to the user that something is actually happening. Animating the cursor means that messages do not need to be printed out to a window, making it a neat and concise way of presenting the desired information. On the Macintosh, work in progress is indicated by a watch icon, with the hands moving round and round, or by a spinning disk. One system uses a stick person apparently doing weightlifting, to show that heavy work is in progress, whilst another has an hourglass trickling down.
Animation is also used in a manner similar to that in cartoons, where animated objects are used to perform particular functions for the user. For example, in an
There are a number of different CD approaches that are primarily distinguished by the different forms of compression they use to get more onto less. CD-I has
Page length is also something that has to be attended to: moving to the scrollbar in the margin and scrolling down is a boring and wearisome task for most users. This implies that the information that has to be presented should be split into screen-sized chunks wherever possible. Such a fine-grained breakdown is different from that utilized in printed media such as books, though more common in newspapers and magazines. The outcome of this small-scale chunking, coupled with hierarchical structuring, is that a Web-based version of information is, and should be, different from the version that would be produced for paper presentation - different media, different constraints, different results. One consequence of this is that, if it is likely that a user will require a paper copy of the information made available over the Web, the user should be able to download it in one go as a single complete file, with the same information content but possibly a different layout. Paper does not have the same inbuilt hypertextual and active capabilities as the web page, and will be accessed in a predominantly linear fashion.
There are only a limited number of text-placing options: text can be left or right justified, or centred. There are a few predefined formatting styles such as ordered and unordered lists that have additional structure, in the form of indentation from
Layout of graphics is done implicitly by the browsers; there is very little explicit layout control available to the designer, much as with text, and designers have to be careful that the graphics appear where they want them to. The comments on screen
Icons often appear on web pages, and while there are many available to choose from, they should be used with care. On web pages, icons are typically used in one of two ways. They are either visual clues, associating some small picture with different parts of the text (for example, some pages have icon-sized characters that appear next to instructions). Alternatively, they are used in much the same way as in a standard WIMP interface to represent aspects of the functionality of the underlying pages. In this latter case, they must represent their associated functionality in either a concrete or an abstract form. This means that the design of the individual icon has to be carefully thought out, as a lot of information may have to be represented in a small area of screen estate. However, icons are rarely seen on their own, and when placed next to their neighbours, the whole effect has to be pleasing rather than disruptive and garish. Therefore, the group of icons have to be designed together, with a coherent and recognizable style. The picture is broader than this, however: other applications also use icons, which has its advantages and disadvantages. One advantage is that certain icons are already associated with specific functionality (for example, a picture of a floppy disk to represent 'save'). Disadvantages are that it restricts the individuality and style icon sets can show, and may mean that icons designed for one purpose are misunderstood by users because they have seen something similar in another context. It is therefore vital that time is spent in examining the way icons are used in other systems, before importing them into web pages or designing new ones.
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