The terms "three-dimensional" (3D or 3-D) and "two-dimensional" (2D or 2-D) are most commonly used in reference to photography and other graphic image technology, such as animation and computer graphics. The difference between 3D and 2D images is that 3D images add the perception of depth. A 2D image, on the other hand, has only height and width. The term "three-dimensional" also is sometimes used to describe a physical item such as a sculpture or mobile, which could be described as three-dimensional art, in comparison with a two-dimensional painting.
Three-dimensional imagery cannot be created without duplicating the effect of two eyes working in tandem, which allows three-dimensional perceptive effects such as depth perception. Early 3D technology imitated this process with dual-camera or dual-lens setups. Modern computer technology can easily create realistic effects in both 3D and 2D.
Photography records images for reproduction on flat, two-dimensional surfaces, such as paper prints or display screens. This has the effect of flattening the image, reducing or eliminating the effect of depth. Natural vision produces this effect because the eyes are set slightly apart, allowing the brain to process two different views of the same image. During the late 19th century, photographers attempted to rectify this problem with dual still and motion cameras that were designed to work in tandem. Viewing these “stereoscopic” images through special viewers simulated the effect of seeing a three-dimensional image.
The terms 3D and 2D first came into popular use because of the film industry. During the 1950s, Hollywood filmmakers experimented with 3D movies as a marketing gimmick. These movies were filmed with a variation on the stereoscopic dual-camera setups. They were expensive to produce and required viewers to wear special glasses to experience the 3D effect. Only a few of these movies became lasting classics, most in the horror/suspense genre, such as House of Wax, Creature from the Black Lagoon and Alfred Hitchcock’s Dial M for Murder.
A second wave of 3D films in the 1980s had similar results. The earliest video games, meanwhile, also had 2D graphics, but in the 1980s and 1990s, rapid advances in computer processing and memory made more realistic images possible. By the 21st century, computer-generated imagery (CGI) could create 3D and 2D effects for big and small screens alike. In 2009, James Cameron’s film Avatar pioneered a new wave of cinematic 3D by combining cutting-edge CGI and digital filmmaking technology. Soon, many of Hollywood’s big-budget effects films were following suit.
In real life, there is another crucial difference between 3D and 2D vision. Three-dimensional vision contributes to depth perception, or the ability to estimate an object’s distance. This fact has been humorously pointed out on the science fiction television series Futurama because one of the show’s main characters, Leela, has only one eye. Despite being the pilot of an interstellar space ship, Leela often complains that she has no depth perception. Ironically, Andre de Toth, the director of the famous 3D film House of Wax, also had only one eye, and he could not see in 3D.