The early adoption and subsequent interest in photorealistic rendering
by the graphics community is most likely due to the "mission
statement'' of photorealistic rendering: "Create an image that is
indistinguishable from a photograph." This mission statement gives
photorealistic rendering a visual "Turing test", and an easily
defined metric for a successful image. Artistic computer graphics does not have a single
mission statement. Instead, researchers are pursuing a number of image
creation goals. The goals of Artistic computer graphics include simulating traditional
artistic media, understanding the human visual system, communicating
effectively with low bandwidth, abstracting images, enhancing
learning, and improving user interaction.
The control of detail in an image for purposes of communication is
becoming the hallmark of artistic computer graphics. Often this control of image
detail is combined with stylization to evoke the perception of
complexity in an image without an explicit representation. Artistic images
also provide a more natural vehicle for conveying information at
different levels of abstraction and detail. Seven occasions
when an artistic computer generated image has an advantage are listed below.
1. Image Reproducibility: In a technical journal printed in black
and white, fully shaded three-dimensional geometry may not print
well. For example, photographic images do not copy or fax as well as
line art images.
2. Medical Visualization: Researchers are focusing on providing
artistic algorithms, which can be manipulated interactively, for real time
visualizations of volume data. A good example is the visualization of
electric fields inside the human body.
3. Communication of Abstract Ideas: The human visual system
expects realistically rendered characters to behave
realistically. Therefore, nonphotorealistic animation can be used to
express ideas beyond the physical and logical norm, in a way that is
acceptable to a general audience. An example of this is force diagrams
used in physics textbooks.
4. Evoking the Imagination: Simple line drawings can communicate
abstract ideas in ways that a photograph cannot. In a photorealistic
image, everything in the scene is rendered in fine detail, leaving
little to the imagination. In comparison, by not depicting every
detail, a nonphotorealistic image allows the viewer to share in the
interpretive process.
5. Animation: When creating an animation it is necessary to focus
the attention of the audience on the relevant actions and elements in
the scene. A viewer inspecting the fine details of a photorealistic
scene can miss the big picture. Most nonphotorealistic techniques
employ an economy of line, limiting the detail in a scene, which makes
directing the attention of the viewers easier for an animator.
6. Compression: By not depicting all the detail required for
photorealistic images, nonphotorealistically rendered computer
graphics images typically take less time to create, can be rendered to
the screen faster, and use less storage space. For example, half-tone
images yield the same shape from shading cues as traditionally
rendered computer graphics images when viewed from a
distance. However, the half-tone images require between one tenth and
one one-hundredth of the storage
space.
7. Communication of Design or Process Completeness:
Photorealistic rendering implies an exactness and perfection that may
overstate the fidelity of the simulated scene to a photograph. Artistic computer graphics
can aid a viewer in understanding that the image they see is only an
approximate depiction of a scene. An excellent example of this
phenomena is architectural rendering. Architects have found that
on-site building conditions and variations in regional building codes
can lead to last minute changes in building plans. If clients are
shown realistic images of the proposed building these last minute
changes can come as a shock, leading to angry, disappointed clients.
However, if the clients are shown nonphotorealistic images of the
proposed building clients tend to accept the design process as
incomplete and the plans as changeable. Therefore, the clients usually
accept on-site changes.
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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