Computer graphics

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A Blender 2.45 screenshot.
A 2D projection of a 3D projection of a 4D Pentachoron performing a double rotation about two orthogonal planes.

Computer graphics are graphics created by computers and, more generally, the representation and manipulation of pictorial data by a computer.


[edit] Overview

The term computer graphics includes almost everything on computers that is not text or sound. Today nearly all computers use some graphics and users expect to control their computer through icons and pictures rather than just by typing.[1] The term Computer Graphics has several meanings:

Today computers and computer-generated images touch many aspects of our daily life. Computer imagery is found on television, in newspapers, in weather reports, and during surgical procedures. A well-constructed graph can present complex statistics in a form that is easier to understand and interpret. Such graphs are used to illustrate papers, reports, theses, and other presentation material. A range of tools and facilities are available to enable users to visualize their data, and computer graphics are used in many disciplines. [2]

[edit] History

In 1960 William Fetter, a graphic designer for Boeing Aircraft Co., was credited with coining the phrase "Computer Graphics" to describe his research at Boeing. Fetter has said that the terms were actually given to him by Verne Hudson at Boeing. In a 1978 interview, Fetter stated that there had been a long-standing need in many applications for a simulation of the human figure that both accurately describes the human body and is adaptable to different user environments. His early work at Boeing focused on the development of such ergonomic descriptions. One of the most memorable and iconic images in the early history of computer graphics was a human figure, often referred to as the "Boeing Man", but referred to by Fetter as the "First Man".[3]

SAGE Sector Control Room.

The field of computer graphics developed with the emergence of computer graphics hardware. Early projects like the Whirlwind and SAGE Projects helped develop the computer graphics discipline by providing the CRT as a viable display and interaction interface, and introduced the light pen as an input device. Further advances in the development of the digital computer such as the TX-2 computer in 1959 at MIT's Lincoln Laboratory led to the further developments in interactive computer graphics. The first interactive computer graphics system used a display, a light pen, and a bank of switches as the interface. The TX-2 integrated a number of new man-machine interfaces. A light pen could be used to draw sketches on the computer and both the Sketchpad interactive computer graphics were born. In the Lincoln Labs on their TX-2 computer Ivan Sutherland's PhD work made him the "grandfather" of interactive computer graphics and graphical user interfaces.[3]

The research at MIT would help shape the early computer and computer graphics industries. Soon major corporations became interested in the technology. TRW, Lockheed-Georgia, General Electric and Sperry Rand are a few of the many computer graphics companies that began in the mid 1960's. IBM quickly responded to this interest by releasing the IBM 2250 graphics terminal, the first commercially available graphics computer.[4]

The organizations, conferences, graphics standards, and publications in the field of computer graphics emerged since the end of the 1960s. In 1969, the ACM initiated a A Special Interest Group in Graphics (SIGGRAPH) devoted to simulation and modeling, to text editing and composition, to computer generated art, cartography and mapping, computer aided design and, computer graphics software and hardware. In 1973, the first annual SIGGRAPH conference was held, which has become one of the focuses of the organization. Over the years, SIGGRAPH grew adding Panels and Courses, an Art Show, and venues for emerging technologies. Several related conferences have occasionally co-located with SIGGRAPH, and an Education track became part of the overall conference offerings.[3]

During the late 1970s, personal computers became more powerful, capable of drawing both basic and complex shapes and designs. In the 1980s, artists and graphic designers began to see the personal computer, particularly the Commodore Amiga and Macintosh, as a serious design tool, one that could save time and draw more accurately than other methods. 3D computer graphics became possible in the late 1980s with the powerful SGI computers, which were later used to create some of the first fully computer-generated short films at Pixar. The Macintosh remains one of the most popular tools for computer graphics in graphic design studios and businesses.

Modern computer systems, dating from the 1980s and onwards, often use a graphical user interface (GUI) to present data and information with symbols, icons and pictures, rather than text. Graphics are one of the five key elements of multimedia technology.

3D graphics became more popular in the 1990s in gaming, multimedia and animation. In 1996, Quake, one of the first fully 3D games, was released. In 1995, Toy Story, the first full-length computer-generated animation film, was released in cinemas worldwide. Since then, computer graphics have become more accurate and detailed, due to more advanced computers and better 3D modelling software applications, such as Cinema 4D.

[edit] Image types

[edit] 2D computer graphics

Raster graphic sprites (left) and masks (right)

2D computer graphics are the computer-based generation of digital images—mostly from two-dimensional models, such as 2D geometric models, text, and digital images, and by techniques specific to them. The word may stand for the branch of computer science that comprises such techniques, or for the models themselves.

2D computer graphics are mainly used in applications that were originally developed upon traditional printing and drawing technologies, such as typography, cartography, technical drawing, advertising, etc.. In those applications, the two-dimensional image is not just a representation of a real-world object, but an independent artifact with added semantic value; two-dimensional models are therefore preferred, because they give more direct control of the image than 3D computer graphics, whose approach is more akin to photography than to typography.

[edit] Pixel art

Pixel art is a form of digital art, created through the use of raster graphics software, where images are edited on the pixel level. Graphics in most old (or relatively limited) computer and video games, graphing calculator games, and many mobile phone games are mostly pixel art.

[edit] Vector graphics

Example showing effect of vector graphics versus raster graphics.

Vector graphics formats are complementary to raster graphics, which is the representation of images as an array of pixels, as it is typically used for the representation of photographic images.[5] There are instances when working with vector tools and formats is best practice, and instances when working with raster tools and formats is best practice. There are times when both formats come together. An understanding of the advantages and limitations of each technology and the relationship between them is most likely to result in efficient and effective use of tools.

[edit] 3D computer graphics

3D computer graphics in contrast to 2D computer graphics are graphics that use a three-dimensional representation of geometric data that is stored in the computer for the purposes of performing calculations and rendering 2D images. Such images may be for later display or for real-time viewing.

Despite these differences, 3D computer graphics rely on many of the same algorithms as 2D computer vector graphics in the wire frame model and 2D computer raster graphics in the final rendered display. In computer graphics software, the distinction between 2D and 3D is occasionally blurred; 2D applications may use 3D techniques to achieve effects such as lighting, and primarily 3D may use 2D rendering techniques.

3D computer graphics are often referred to as 3D models. Apart from the rendered graphic, the model is contained within the graphical data file. However, there are differences. A 3D model is the mathematical representation of any three-dimensional object (either inanimate or living). A model is not technically a graphic until it is visually displayed. Due to 3D printing, 3D models are not confined to virtual space. A model can be displayed visually as a two-dimensional image through a process called 3D rendering, or used in non-graphical computer simulations and calculations.

[edit] Computer animation

An example of Computer animation produced using Motion capture

Computer animation is the art of creating moving images via the use of computers. It is a subfield of computer graphics and animation. Increasingly it is created by means of 3D computer graphics, though 2D computer graphics are still widely used for stylistic, low bandwidth, and faster real-time rendering needs. Sometimes the target of the animation is the computer itself, but sometimes the target is another medium, such as film. It is also referred to as CGI (Computer-generated imagery or computer-generated imaging), especially when used in films.

To create the illusion of movement, an image is displayed on the computer screen then quickly replaced by a new image that is similar to the previous image, but shifted slightly. This technique is identical to the illusion of movement in television and motion pictures.

[edit] Concepts and Principles

[edit] Image

In common usage, an image or picture is an artifact, usually two-dimensional, that has a similar appearance to some subject—usually a physical object or a person. Images may be two-dimensional, such as a photograph, screen display, and as well as a three-dimensional, such as a statue. They may be captured by optical devices—such as cameras, mirrors, lenses, telescopes, microscopes, etc. and natural objects and phenomena, such as the human eye or water surfaces.

A digital image is a representation of a two-dimensional image using ones and zeros (binary). Depending on whether or not the image resolution is fixed, it may be of vector or raster type. Without qualifications, the term "digital image" usually refers to raster images.

[edit] Pixel

In the enlarged portion of the image individual pixels are rendered as squares and can be easily seen.

In digital imaging, a pixel is the smallest piece of information in an image.[6] Pixels are normally arranged in a regular 2-dimensional grid, and are often represented using dots or squares. Each pixel is a sample of an original image, where more samples typically provide a more accurate representation of the original. The intensity of each pixel is variable; in color systems, each pixel has typically three or four components such as red, green, and blue, or cyan, magenta, yellow, and black.

[edit] Graphics

Graphics are visual presentations on some surface, such as a wall, canvas, computer screen, paper, or stone to brand, inform, illustrate, or entertain. Examples are photographs, drawings, line art, graphs, diagrams, typography, numbers, symbols, geometric designs, maps, engineering drawings, or other images. Graphics often combine text, illustration, and color. Graphic design may consist of the deliberate selection, creation, or arrangement of typography alone, as in a brochure, flier, poster, web site, or book without any other element. Clarity or effective communication may be the objective, association with other cultural elements may be sought, or merely, the creation of a distinctive style.

[edit] Rendering

Rendering is the process of generating an image from a model, by means of computer programs. The model is a description of three dimensional objects in a strictly defined language or data structure. It would contain geometry, viewpoint, texture, lighting, and shading information. The image is a digital image or raster graphics image. The term may be by analogy with an "artist's rendering" of a scene. 'Rendering' is also used to describe the process of calculating effects in a video editing file to produce final video output.

3D projection
3D projection is a method of mapping three dimensional points to a two dimensional plane. As most current methods for displaying graphical data are based on planar two dimensional media, the use of this type of projection is widespread, especially in computer graphics, engineering and drafting.
Ray tracing
Ray tracing is a technique for generating an image by tracing the path of light through pixels in an image plane. The technique is capable of producing a very high degree of photorealism; usually higher than that of typical scanline rendering methods, but at a greater computational cost.
Example of shading.
Shading refers to depicting depth in 3D models or illustrations by varying levels of darkness. It is a process used in drawing for depicting levels of darkness on paper by applying media more densely or with a darker shade for darker areas, and less densely or with a lighter shade for lighter areas. There are various techniques of shading including cross hatching where perpendicular lines of varying closeness are drawn in a grid pattern to shade an area. The closer the lines are together, the darker the area appears. Likewise, the farther apart the lines are, the lighter the area appears. The term has been recently generalized to mean that shaders are applied.
Texture mapping
Texture mapping is a method for adding detail, surface texture, or colour to a computer-generated graphic or 3D model. Its application to 3D graphics was pioneered by Dr Edwin Catmull in 1974. A texture map is applied (mapped) to the surface of a shape, or polygon. This process is akin to applying patterned paper to a plain white box. Multitexturing is the use of more than one texture at a time on a polygon.[7]

[edit] Volume rendering

Volume rendered CT scan of a forearm with different colour schemes for muscle, fat, bone, and blood.

Volume rendering is a technique used to display a 2D projection of a 3D discretely sampled data set. A typical 3D data set is a group of 2D slice images acquired by a CT or MRI scanner.

Usually these are acquired in a regular pattern (e.g., one slice every millimeter) and usually have a regular number of image pixels in a regular pattern. This is an example of a regular volumetric grid, with each volume element, or voxel represented by a single value that is obtained by sampling the immediate area surrounding the voxel.

[edit] 3D modeling

3D modeling is the process of developing a mathematical, wireframe representation of any three-dimensional object via specialized software. The product is called a "3D model". It can be displayed as a two-dimensional image through a process called 3D rendering or used in a computer simulation of physical phenomena. The model can also be physically created using 3D Printing devices. Models may be created automatically or manually. The manual modeling process of preparing geometric data for 3D computer graphics is similar to plastic arts such as sculpting.

[edit] Pioneers in graphic design

Charles Csuri
Charles Csuri is best known for pioneering the field of computer graphics, computer animation and digital fine art, creating the first computer art in 1964. Csuri has been recognized as the father of digital art and computer animation by Smithsonian, and as a leading pioneer of computer animation by the Museum of Modern Art (MoMA) and The Association for Computing Machinery Special Interest Group Graphics (ACM-SIGGRAPH).
Donald P. Greenberg
Donald P. Greenberg is an internationally recognized pioneer in computer graphics, Greenberg has authored hundreds of articles and served as a teacher and mentor to many prominent computer graphic artists and animators. Five former students have won Academy Awards for Scientific or Technical Achievements, five have won the SIGGRAPH Achievement Award, and many now work for Pixar Animation Studios. Greenberg was the founding director of the National Science Foundation Science and Technology Center for Computer Graphics and Scientific Visualization when it was created in 1991. His former students include Robert L. Cook, Marc Levoy, and Wayne Lytle.
A. Michael Noll
Noll was one of the first researchers to use a digital computer to create artistic patterns and to formalize the use of random processes in the creation of visual arts. His initial digital computer art was programmed in the summer of 1962 at Bell Telephone Laboratories in Murray Hill, NJ, making him one of the earliest digital computer artists. In 1965 Noll along with two other pioneers within the field of early computer art, Frieder Nake and Georg Nees in Germany, were the first to exhibit publicly their computer art. During April 1965, the Howard Wise Gallery in New York City exhibited Noll's computer art along with random-dot patterns by Bela Julesz.
Other pioneers

[edit] The study of computer graphics

[edit] Computer graphics

A modern render of the Utah teapot, an iconic model in 3D computer graphics created by Martin Newell in 1975.

The study of computer graphics is a sub-field of computer science which studies methods for digitally synthesizing and manipulating visual content. Although the term often refers to three-dimensional computer graphics, it also encompasses two-dimensional graphics and image processing.

As an academic discipline, computer graphics studies the manipulation of visual and geometric information using computational techniques. It focuses on the mathematical and computational foundations of image generation and processing rather than purely aesthetic issues. Computer graphics is often differentiated from the field of visualization, although the two fields have many similarities.

[edit] Connected studies

Connected studies include:

[edit] Applications

[edit] References

[edit] Further reading

  • James D. Foley, Andries Van Dam, Steven K. Feiner and John F. Hughes (1995). Computer Graphics: Principles and Practice. Addison-Wesley
  • Donald Hearn and M. Pauline Baker (1994). Computer Graphics. Prentice-Hall.
  • Francis S. Hill (2001). Computer Graphics. Prentice Hall.
  • John Lewell (1985). Computer Graphics: A Survey of Current Techniques and Applications. Van Nostrand Reinhold.
  • Jeffrey J. McConnell (2006). Computer Graphics: Theory Into Practice. Jones & Bartlett Publishers.
  • R. D. Parslow, R. W. Prowse, Richard Elliot Green (1969). Computer Graphics: Techniques and Applications.
  • Peter Shirley and others. (2005). Fundamentals of computer graphics. A.K. Peters, Ltd.
  • M. Slater, A. Steed, Y. Chrysantho (2002). Computer graphics and virtual environments: from realism to real-time. Addison-Wesley

[edit] External links

Look up computer graphics in Wiktionary, the free dictionary.

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