A greeble or nurnie is a small piece of detailing added to break up the surface of an object to add visual interest to a surface or object, particularly in movie special effects. They serve no real purpose other than to add complexity to the object, and cause the flow of the eye over the surface of the object to be interrupted, usually giving the impression of increased size. It is essentially the small detailed technical part of a larger object. The detail can be made from geometric primitives, including cylinders, cubes, and rectangles, combined to create intricate, but meaningless, surface detail.

Greebles are commonly found on models or drawings of fictional spacecraft in science fiction. The earliest recorded use of the term ‘greeble’ found to date was by those working on the special effects for ‘Star Wars’ — the group who would later become Industrial Light and Magic. They also described this design method as ‘guts on the outside.’ Ron Thornton is widely believed to have coined the term ‘nurnies’ referring to CGI technical detail that his company Foundation Imaging produced for the ‘Babylon 5’ series.

In physical models, these greebles could be anything from parts of plastic cut to an interesting shape, or actual elements taken from shop bought model kits. For instance, in ‘Star Wars’ the original Imperial Star Destroyer was constructed from a plywood frame and adorned with sheet styrene. Panel lines were cut into the sheet styrene, but essentially that left the ship looking extremely bare. Hundreds of model kits were purchased and the model department promptly took pieces of the model kits and cut them up and stuck them along with more sheet styrene to the surfaces of the ship. The ultimate effect was to make the ship appear more believable to the viewer through the addition of these large areas of ancillary details. The greebles themselves served no purpose other than to fill space and individually had no definite function to the design of the ship, although later each greeble was given a specific function by either fans or technical illustrators for fan guides.

An anecdote from the creation of the first Star Wars movie involves the Tunisian customs enquiring what a part of C-3PO’s costume (listed as ‘assorted greebles’) was. Their response was allegedly ‘Something that looks cool but doesn’t actually do anything.’ As would be expected, given these origins, greebling is most commonly associated with the particular kind of large city-like spaceships made popular in ‘Star Wars,’ but has been generalized to refer to any dense covering by different (usually mechanical) components. Similarly, Borg starships (and drones) in ‘Star Trek’ appear heavily ‘greebled’ using leftover sprues from previous kitbashing and photoetch bits.

In 3D computer graphics, greebles can be created automatically by specific software, in order to avoid the time consuming process of manually creating large numbers of precise, custom geometry. Some consider it a task best suited to automatic, software based procedural generation, particularly if a great degree of control is unnecessary or the greebles will not be particularly large on screen. Most greeble generating software work by sub-dividing the surface to be greebled into smaller regions, adding some detail to each new surface, and then recursively continuing this process on each new surface to some specified level of detail. Similar algorithms are used in the creation of fractal surfaces.

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