Three-dimensional NPR is the style that is most commonly seen in video games and movies. The output from this technique is almost always a 3D model that has been modified from the original input model to portray a new artistic style. In many cases, the geometry of the model is identical to the original geometry, and only the material applied to the surface is modified. The majority of NPR techniques applied to 3D geometry are intended to make the scene appear two-dimensional.
The input to a two-dimensional NPR system is most commonly an image; however, there are systems that take 3D geometry information as input and produce a 2D image or video as output. Again, many of the systems are intended to mimic a desired artistic style, such as watercolor, impressionism, or pen and ink drawing.
The most useful illustrations in technical illustrations are not necessarily photorealistic. Non-photorealistic renderings, such as exploded view diagrams, greatly assist in showing placement of parts in a complex system.
Users who are interested in having much more control in the NPR process may be more interested in interactive techniques. Many of these NPR systems provide the user with a canvas that they can "paint" on using the cursor - as the user paints, a stylized version of the image is revealed on the canvas. This is especially useful for people who want to simulate different sizes of brush strokes according to different areas of the image.
In contrast to the methods mentioned previously, another technique in NPR is simulating the painter's medium. Methods include simulating the diffusion of ink through different kinds of paper, and also of pigments through water for simulation of watercolor.
The term "non-photorealistic rendering" was probably coined by David Salesin and Georges Winkenbach in a 1994 paper. Many researchers find the terminology to be unsatisfying; some of the criticisms are as follows:
The first conference on Non-Photorealistic Animation and Rendering included a discussion of possible alternative names. Among those suggested were "expressive graphics", "artistic rendering", "non-realistic graphics", "art-based rendering", and "psychographics". All of these terms have been used in various research papers on the topic, but the term NPR seems to have nonetheless taken hold.
Some key papers in the development of NPR are:
Agency Reviews Patent Application Approval Request for "Non-Photorealistic Rendering of Geographic Features in a Map"
Oct 03, 2013; By a News Reporter-Staff News Editor at Politics & Government Week -- A patent application by the inventors Giencke, Peter W....
Wipo Publishes Patent of Google for "Non-Photorealistic Rendering of Geographic Features in a Map" (American Inventors)
Sep 13, 2013; GENEVA, Sept. 13 -- Publication No. WO/2013/134108 was published on Sept. 12.Title of the invention: "NON-PHOTOREALISTIC...
WIPO ASSIGNS PATENT TO INDUSTRY-ACADEMIC COOPERATION FOUNDATION, YONSEI UNIVERSITY FOR "APPARATUS AND METHOD FOR GENERATING NON-PHOTOREALISTIC IMAGE USING NON-PHOTOREALISTIC RENDERING, AND RECORDING MEDIUM WHEREIN PROGRAM FOR IMPLEMENTING THE METHOD IS RECORDED" (SOUTH KOREAN INVENTORS)
Dec 01, 2010; GENEVA, Dec. 1 -- Publication No. WO/2010/134675 was published on Nov. 25. Title of the invention: "APPARATUS AND METHOD FOR...