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by Juan C. Dürsteler [message nº 163]

Animation permits the representation of change, including time in the visual equation. In this issue we review the basic variables of animation and the profit we can extract from its use.
Blocksplash, a single photogram of an animation that shows a silver block catapulting several wooden cubes against a wall of water.
: Image as can be seen at Mark Carlson's web page.

Animation (see glossaery definition) is the outcome of the process of taking a series of individual images concatenating them into a temporised sequence in such a way that it gives the sensation of continuous movement.

Because of their very nature static images pose difficulties to the expression of change that is consubstantial to the passing of time. In many cases the only way to represent said change is in a conceptual way, maybe joining with arrows (the graphic object typically conveying direction and change) the transformed or moved elements.

Animation, very simple conceptually, nevertheless allows you to visualise the flow of change in structures and complex spatial relationships and even is able to depict causality properly (see issues number 18 and number 152).

We can count, at least, two main uses of animation:

  • Visual narrative
    When speaking of animation, what immediately comes to mind is the ideas associated to movies, from cartoons to the most recent achievements of computer generated movies. Visual narrative, to tell stories, sequences of events. Cinema, which is nothing more than a way to animate photographs, exemplifies the use of animation in visual narrative. See for example the animation movies at the Open Directory

  • Process Visualisation
    A process is, by definition, the description of a series of changes with time. It can be the manufacturing of a certain good, the changes that occur in the development of natural phenomena, or the set of operations that one has to perform to get the desired outcome. Animation are very useful here in order to ease the understanding of intermediate steps that lead to the final outcome. Examples of this are videos like the description of the movements of the continental drift of the University of California in Berkeley or the fantastic images of the collision of galaxies created by Summers, Mihos and Hernquist. Not to miss the excellent animations you can find at the animation group of the GVU Center at Georgia Tech.

    The goal in these cases is mainly didactic, it's all about learning/discovering by seeing.
ColGalax.jpg (13451 bytes)
Collision between galaxies, extraordinary animation by F. Summers, C. Mihos y L. Hernquist.
Source: Image as can be seen at the Hubblesite.org webpage.
Balls sinking into water and collision of two balls in a pool, photograms of two animations illustrating the interaction between rigid solids and fluids.
: Image as can be seen at Mark Carlson's webpage.

Hayward* in his book “Computers for animation” specifies the basic variables of animation that we, following authors like Magnenat-Thalman and others, group into, at least, two categories, as pertaining to graphic objects or to animation elements:

  • Graphic objects
    are the carriers of static information in each photogram. They coincide approximately with Jacques Bertin concept of visual variables.
    • Size:
      In many cases size is associated to the value of a certain variable. Therefore the changes of a certain variable in time can be associated with changes of size (length, area or volume) of a graphic object.

    • Shape:
      The shape of objects are used to encode their inclusion into a category or to a data series, for example triangles for a certain category and rhomboids for another one. In cartography the projection means that some countries change shape depending on which one we are using. The changing shape allows you to visualise changes in data when considering a different category or when seen with a different projection.

    • Texture, pattern, colour.
      These are graphical variables that, like shape or size allow us to encode certain variables of our problem incorporating informative richness to the animation. For example the change in colour of an object representing a chat can be helpful to distinguish the peak moments of participation when the chat is "hot" (in red) from those of little participation when we can say that it's "cold" (in blue).

    • Position and orientation
      The location of a point regarding the visualisation space represents the values of a set of variables, i.e., their coordinates. Because of this the movement of a point can very effectively show the change of the many values that it can represent. For example a dot moving in 2D can be showing the increase of value of sticker in the stock exchange along with its liquidity. The variation of "point" in parallel coordinates can give an idea of the changes occurring in a great deal of variables (for parallel coordinates see issue number 54)

  • Animation elements
    are the elements that enable the representation of change
    • Speed
      Speed provides the notion of the rate of change with time of a certain variable. Acceleration gives the rate of change of speed. Both quantities allow us to easily show the rate of change, for example, to represent the way and rate the population of many countries has concentrated in the cities as time went by.

    • Viewpoint
      The camera's position and orientation (the specification of our visualisation) provides us with the focus of our attention. The movement of the camera to look at a different direction enables us to change the focus of our attention to accentuate another aspect or topic of what we are dealing with.

    • Distance
      The change of this element enables a natural zoom. Again it allows us to refocus our attention on a partial aspect of the change or on a general view of the same (seeing the focus or the context. To a certain extent it acts as a change of scale.

    • Scene
      Here Hayward refers to the use of special visual effects like fading mix or wipe to produce the transition between one scene and the following one indicating the transition from one topic to another, marking a change of subject in the visual narrative.

Animation has evolved quickly in the last few years as the many movies that include animation or that are made completely of animations can testify. Many outstanding examples of simulation and visualisation of natural phenomena or complex processes have come to light in the last few years too.

The ensemble of visualization, animation and interaction make a very powerful trio both for the discovery of knowledge hidden in the data and for the transmission of the existing knowledge.

Hayward, S. (1984) Computers for animation. Norwich: Page Bros. Ltd

Links of this issue:

http://www.cc.gatech.edu/~carlson/   Mark Carlson's web page
http://www.infovis.net/printRec.php?rec=glosario&lang=2#Animacion   Glossary entry about Animation
http://www.infovis.net/printMag.php?num=18&lang=2   Issue 18 An image is worth 1000 words
http://www.infovis.net/printMag.php?num=152&lang=2   Num 152 about Simulators and Dynamic Visualisation
http://dmoz.org/Arts/Animation/Movies/   Open directory entry for Animation movies
http://www.ucmp.berkeley.edu/geology/anim1.html   Continental drift animation
http://hubblesite.org/newscenter/newsdesk/archive/releases/2002/09/video/a   Galaxy collision video at Hubblesite.org
http://www.cc.gatech.edu/gvu/animation/   Georgia Tech Animation Group
http://hubblesite.org/newscenter/newsdesk/archive/releases/2002/09/   Hubblesite page with individual photograms of the video
http://www.infovis.net/printMag.php?num=54&lang=2   Issue 54 City'O'Scope (parallel coordinates)
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