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Submitted by ajalon on 29 March 2010 - 11:34am
There are some operational features you might consider implementing: stepwise or continuous control, speed control, and undo/redo.
The fundamental operation of an AV is to display a series of events. Depending on how long and involved the series is, and how much the user has to understand, the user might need more or less control over the pacing. For example, if the "event" is just the movement of an object from one position to another, this might be conveyed by a smooth animation. Such "small scale" animations should be controlled by a speed control so that the user can make the animation go fast or slow. Learners can slow down the difﬁcult parts; educators making a presentation can scale the speed to their speech. Everyone gets bored with watching the same thing over and over if goes too slow.
Stepwise vs. Continuous Operation
When a longer series of events is presented, particularly if they contain key content that the user is meant to understand, then it becomes important to give the user control over the pacing of the presentation. The most extreme case is when the "series of events" is the entire algorithm or operation. Many AVs of the past were essentially movies, which gave the user no interaction or control other than the speed of the interaction. In general, the potential of AVs is best realized when users are more engaged, and in control of the information ﬂow. Being able to control the pace might not seem terribly interactive, but it is a crucial step toward engagement. User studies (see Saraiya 2004) show that there is a signiﬁcant improvement in learning outcome when an animation is broken into pieces by providing a "next" button" to let the user move from step to step at their pace.
As with all human-computer interactions, undo and redo are nice features to include where appropriate. Especially if you allow user-entered data, at least one level of undo would be ideal.