Two-dimensional, or 2D, computer graphics appear flat on the screen and are viewed from only one angle. Old arcade games, such as Pac-Man, offer an accurate representation of 2D graphics. Pac-Man's character and the ghosts that chase him appear as flat shapes seen from only one side regardless of where he moves on the screen. A newer computer or video game, in contrast, features characters which appear three-dimensional, or 3D, and can turn in circles so the viewer can see them from all angles. 3D graphics create the illusion of having depth, despite the fact that they are technically still flat images on a screen, while a 2D computer graphic does not create this illusion of depth and, instead, simply shows a flat shape or outline.
To create a 2D computer graphic, the artist combines shapes, colors, and lines into an image meant for viewing on a computer screen. The image is seen head-on from one angle. This could be from behind, beside, in front, or even from above the character, but the character still appears flat. The angle the character is drawn at and the shading around him may create a subtle illusion of being 3D, but he is still a single, flat image.
In contrast to a 2D image, a 3D image is built around a wireframe. This is a mesh-like model of lines that create geometric shapes, such as spheres, around which texture and color are applied. This creates a 3D character that can move and be seen from multiple angles. It takes more computer power to generate a 3D image than a 2D image.
Typically, a 2D computer graphic is made from a standard image while a 3D computer graphic is made from a vector image. Vector images scale and resize to fit their container, in this case the computer screen. 2D computer graphics are drawn out like illustrations in a book and stay the same size. Newer technology allows for 2D images to be vectors and scale up and down, but this is essentially the same as drawing a flat image and then drawing it in multiple sizes. The 3D image, in contrast, must also scale the shading and highlighting on the object to fit the new size.
With computers and technology constantly pushing the limits of what they can produce, most images today are 3D and use smaller 2D computer graphics when necessary. A character's armor might use a 2D computer graphic as a logo painted on it, while a flag might have a 2D computer graphic as its symbol. Creating 3D objects, in comparison to 2D objects, relies strongly on mathematics to calculate how each piece should fit together and move within its environment. A symbol on a building does not have to change, while a person running needs to show realistic arm and leg movements as well as movement in the person's hair flowing behind them.