Wednesday, May 20, 2009

The Purpose of Computer Generated Images and Video

Traditionally, the goal of computer graphics has been photo-realism; to generate synthetic images that are indistinguishable from photographs. Today, this goal has arguably been achieved. Given enough time computers can generate imagery that is indistinguishable from photographic images to the naked eye, and models exist that simulate optical processes down to the level of individual photons. Generating computer images that are indistinguishable from photographs is essential for a host of applications including design, marketing, and the entertainment industry. In many applications, however, an artistic image has advantages over a photorealistic image. Artistic images omit extraneous detail, focus attention on relevant features, clarify, simplify, and disambiguate shape, and show hidden parts. This has lead an increasing number of scientists to question realism as the only goal for computer graphics, and ask: What are the images we create used for?

If the purpose of an image is simulation of physical interaction between light and matter (for research, realistic conceptualization, or entertainment), then photo-realism is a logically sound choice. If, on the other hand, the purpose is more general or abstract (to convey an idea, to give directions, to explain a situation, to give an example) then photo-realism may confuse the issue at hand through unnecessary specificity, visual clutter (masking), and physical limitations. For example, the spatial layout map of a subway system does not include every bend and corner (specificity) because only the stations and their relative positions are of interest to the viewer. The map does not include all the buildings and streets where the subway runs (visual clutter) because this would make it difficult to see the subway paths. Lastly, the map could not have been captured in a single photograph (physical limitation) because most parts of the subway system are underground and mutually hidden.


The Three types of Artistic Computer Graphics

We use the classification system of the Gooch and Gooch textbook that identifies three areas of Artistic computer graphics: (1)~Natural media simulation; (2)~Computer Tools for Artists; and (3)~Artistic style simulation.

Natural media simulation: Artistic rendering gives the graphics community freedom to choose media in addition to a camera for creating images. Natural media simulation concerns itself with simulating (realistically) the substance that is applied to an image (e.g. oil, acrylic, coal), the instruments with which the substance is applied (e.g. brush, pencil, crayon), and the substrate to which the substance is applied (e.g. canvas, paper). In all cases, the simulated media is intended to produce surface marks that are indistinguishable from the real media.

A common assumption in the graphics community is that artistic rendering only involves simulating natural artistic media. This assumption is not surprising, because the first research in the field focused on reproducing traditional art forms, such as pen and ink, watercolor, and oil on canvas. Technology development in any field first seeks to imitate the previous mode of working. Thus, Artistic rendering seems to be following the usual development scheme. Artistic rendering currently embraces a wider scope of research. For example, a recent trend in artistic rendering research is interactive techniques. Current work focuses on the detection and rendering of feature lines to communicate shape. Silhouettes, surface and texture boundary lines, as well as creases are important for communicating the shape of an object.

Computer Tools for Artists: Simulated media itself is of little practical use if it is not controlled by some entity. One of the most important skills for an artist to learn is choosing the correct medium for a given subject. Artists make these choices guided by considerations such as aesthetic appeal and the effectiveness of the medium in communicating the required visual message. Assisting users in creating images is therefore a worthwhile endeavor. Commercial products, such as Photoshop or CorelDraw provide a rich set of tools and functionality by re-purposing standard input devices (mouse, keyboard, digital tablet). Other software and research work assist users with technically challenging, tedious, or repetitive tasks, but ultimately the user still has to create the image and therefore make all decisions about layout, design, placement, etc.

Artistic Styles: The last category of NPR research takes inspiration from existing artistic styles and attempts to automatically transform some data (usually geometric models or photographs) into images in a given artistic style. Examples of this work include the creation of line drawings from three-dimensional models, light-models for cartoon-like shading, and painterly systems from geometric models, videos or photographs.

It should be noted that none of these systems presumes to create Art, they merely generate images that (as realistically as possible) resemble a particular artistic style. In short, much of Artistic computer graphics research is still devoted to realistic picture (as opposed to photo) creation.



May 21, 2009
Author Info:
Dr. Bruce Gooch is the President of Toon-FX, a software company whose products allow users to automatically create cartoon representations of their digital photographs and video. Visit http://www.Toon-FX.com to learn more.
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