"Virtual Reality can be viewed as a field which can draw upon the principles of direct manipulation for Human-Computer Interaction (HCI) design or as an example or extension of direct manipulation itself. In VR, not only can task objects and actions be naturally represented, the task environment can be naturally represented as well. With either view, an understanding of direct manipulation principles is essential for the successful design of human computer interfaces in virtual environments."
Michael Dennehy
"A favorite example to elucidate direct manipulation principles in contrast with the intermediary style of interaction (eg. traditional keyboard based, command driven interfaces), is travel in a car. With direct manipulation, you drive the car by manipulating the steering wheel and pedals. The car responds immediately to your actions, and these responses are immediately evident. If you are making a mistake such as turning too sharply, you can quickly recognize this and perform a corrective measure. With an intermediary style of interaction, you sit in the backseat of the car giving a stranger directions. Further, imagine the stranger possessing poor interpersonal skills and having a limited vocabulary. You've lost the feel for the road and you don't have a direct view of where you are going. Worse yet, you have to rely on a stranger who, if they don't receive explicit directions using particular phrases in a fixed order, idles in the middle of the road or takes you to unfamiliar places from which you don't know the way out."
Michael Dennehy
"Because these benefits of direct manipulation are also desired in VR systems, direct manipulation principles should be drawn from when designing VR systems especially in the use of VR's special input devices. For instance, when using a data glove, a person should be able to select actions rapidly and easily by pointing and gesturing. Gestures should be natural and intuitive in the particular virtual environment. Actions should be represented visually and be incremental, immediate, and reversible to give a person the impression of acting directly in an environment."
Michael Dennehy
Fundamental units of visual communication:
Retinal variables:
Size
Value (saturation/opacity)
Orientation
Texture
Shape
Position
Color
Two types of retinal variables:
An associative variable does not affect the visibility of other dimensions (e.g. we can recognize color regardless of orientation.)
Hue, Orientation, Texture, Shape, Position are associative.
A dissociative variable significantly affect the visibility of other dimensions (e.g. its hard to determine color of a thin line or small dot).
Size and Value are dissociative (they dominate perception and disrupt processing of other correlated dimensions)
Scale of measurement for each variable:
Categorical: Distinct categories should be obvious. For example, different states, jobs, or students.
Which variables can be used for categorical scale?
Ordered: Determine relative ordering. For example, you rate your professor on the scale: good, medium, bad
Position, size, and value are ordered
Quantitative: Determine amount of difference between
ordered values. For example, family income in US dollars.
Position and size are quantitative
This is the bar charts of the population of the USA over the last 8 years. The left chart shows how 3D hurts the visualization. The right chart is a less fancy but much more effective in 2D.
Pay attentions to the y-axis on the following charts of the same data.
Here is an example how visualization lies: from Time Magazine (4/9/79) via Tufte. Please avoid this.
Pie charts:
These examples are charts from a recent version of Excel. 3D distorts the view making it more difficult (less accurate as well) to read the visualization.
A 2D version is much better. Picking up the right colors is also helpful: we could use colors to relate consoles. For example, Playstation 2 and Playstation 3 are both in (darker and lighter) blue.
