A 3D computer graphic is an image that uses computer software to create objects in virtual three-dimensional (3D) space. This is in contrast to two-dimensional (2D) images that exist only as flat images that may use visual tricks, such as perspective, to create the illusion of three-dimensionality. A 3D computer graphic is typically created by artists through the creation of a 3D model, consisting of a wireframe and polygons, which is then usually textured and lit before being rendered.
Often referred to simply as computer graphics (CG) or computer generated imagery (CGI), a 3D computer graphic is created using computer software that is developed specifically for creating 3D graphics. This type of imagery was originally created solely through mathematic algorithms and equations. Modern 3D imagery, however, is made through the use of software that presents a graphical user interface (GUI) to the artist, which allows a 3D computer graphic to be made without direct interaction between the artist and the mathematical properties of the image.
The creation of a 3D computer graphic typically begins with modeling the object that will appear in the final image. A cube, for example, can be created quite simply and, like all 3D imagery, consists of a wireframe and polygons. The wireframe is the basic shape of the object consisting of various points and the lines connecting those points. This can be easily imagined as what the object would look like if it was made out of chicken wire.
Polygons are the shapes, also called faces, which fill in the wireframe to create a solid 3D computer graphic. Using the example of a cube, the corners would be made of the points and lines of the wireframe, while the actual sides of the cube would be polygons or faces. This form is then textured, which means that images are applied to the polygons to provide it with an appearance beyond a single color. Such textures can include: simple graphics, such as an illustration of wood grain; bump mapping, which would provide a sense of depth to the creases in the grain; and reflection maps, which provide shininess to textures like glass and metal.
Once the object is modeled and textured, then lighting can be added to give the object shadows and highlights. This scene is then rendered to create a 3D computer graphic. During rendering, the various elements in the scene are composited and compiled to create an image file that can be used to share and view the 3D computer graphic scene. Many professional studios have groups of computers used only for rendering, as this process can take a long time and often requires a great deal of processing power.