What is visualisation?

Perhaps we can split this into two questions.

Firstly, what is data visualisation? This is the activity of presenting data (from whatever source, in whatever field of study) into some sort of visual format that enhances - or even allows- one's ability to interpret those data. This can range from a simple two-dimensional graph, to a fully immersive, virtual-reality-based environment involving advanced soiftware, multiple projectors, haptics devices and real-time computational steering. In short, presenting data in such a way that allows us to use our eyes, and the brain's associated visual processing, to look for patterns and relationships in data.

Second, what is visualisation, in a more general context? This is a wider and less defined concept. It is, perhaps, the development or presentation of some idea or concept in a visual form. This can range from a presentation of an architectural design via a sketch or, more commonly these days, as a three-dimensional image; to computer-generated imagery that is used in the film industry. The source (i.e. that which is to be visualised) does not need to be data (which we most often think of as being numerical data); it is just something which needs to be, or is better expressed or presented, in a visual form.

More and more, visualisation is being achieved through software. This is especially the case for data visualistion, where many specific software applications have been written explicitly for the purpose of visualising numerical data (examples include AVS Express, Open DX, Visualisation Toolkit, and many more).