Computer-generated imagery

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Morphogenetic Creations computer-generated digital art exhibition by Andy Lomas at Watermans Arts Centre, west London, in 2016. Morphogenic digital art exhibition by Andy Lomas at Watermans Arts Centre, London.jpg
Morphogenetic Creations computer-generated digital art exhibition by Andy Lomas at Watermans Arts Centre, west London, in 2016.

Computer-generated imagery (CGI) is the application of computer graphics to create or contribute to images in art, printed media, video games, films, television programs, shorts, commercials, videos, and simulators. The images may be dynamic or static, and may be two-dimensional (2D), although the term "CGI" is most commonly used to refer to the 3-D computer graphics used for creating characters, scenes and special effects in films and television, which is described as 'CGI animation'.

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The evolution of CGI led to the emergence of virtual cinematography in the 1990s where the vision of the simulated camera is not constrained by the laws of physics. Availability of CGI software and increased computer speeds have allowed individual artists and small companies to produce professional-grade films, games, and fine art from their home computers.[ citation needed ]

The term virtual world refers to agent-based, interactive environments, which are now[ when? ] created with CGI.

Static images and landscapes

Fractal landscape FractalLandscape.jpg
Fractal landscape

Not only do animated images form part of computer-generated imagery, natural looking landscapes (such as fractal landscapes) are also generated via computer algorithms. A simple way to generate fractal surfaces is to use an extension of the triangular mesh method, relying on the construction of some special case of a de Rham curve, e.g. midpoint displacement. [1] For instance, the algorithm may start with a large triangle, then recursively zoom in by dividing it into four smaller Sierpinski triangles, then interpolate the height of each point from its nearest neighbors. [1] The creation of a Brownian surface may be achieved not only by adding noise as new nodes are created but by adding additional noise at multiple levels of the mesh. [1] Thus a topographical map with varying levels of height can be created using relatively straightforward fractal algorithms. Some typical, easy-to-program fractals used in CGI are the plasma fractal and the more dramatic fault fractal. [2]

Many specific techniques been researched and developed to produce highly focused computer-generated effects — e.g., the use of specific models to represent the chemical weathering of stones to model erosion and produce an "aged appearance" for a given stone-based surface. [3]

Architectural scenes

A computer-generated image featuring a house at sunset, made in Blender Lone House.jpg
A computer-generated image featuring a house at sunset, made in Blender

Modern architects use services from computer graphic firms to create 3-dimensional models for both customers and builders. These computer generated models can be more accurate than traditional drawings. Architectural animation (which provides animated movies of buildings, rather than interactive images) can also be used to see the possible relationship a building will have in relation to the environment and its surrounding buildings. The rendering of architectural spaces without the use of paper and pencil tools is now a widely accepted practice with a number of computer-assisted architectural design systems. [4]

Architectural modeling tools allow an architect to visualize a space and perform "walk-throughs" in an interactive manner, thus providing "interactive environments" both at the urban and building levels. [5] Specific applications in architecture not only include the specification of building structures (such as walls and windows) and walk-throughs but the effects of light and how sunlight will affect a specific design at different times of the day. [6]

Architectural modeling tools have now become increasingly internet-based. However, the quality of internet-based systems still lags behind that of sophisticated in-house modeling systems. [7]

In some applications, computer-generated images are used to "reverse engineer" historical buildings. For instance, a computer-generated reconstruction of the monastery at Georgenthal in Germany was derived from the ruins of the monastery, yet provides the viewer with a "look and feel" of what the building would have looked like in its day. [8]

Anatomical models

A CT pulmonary angiogram image generated by a computer from a collection of x-rays SADDLE PE.JPG
A CT pulmonary angiogram image generated by a computer from a collection of x-rays

Computer generated models used in skeletal animation are not always anatomically correct. However, organizations such as the Scientific Computing and Imaging Institute have developed anatomically correct computer-based models. Computer generated anatomical models can be used both for instructional and operational purposes. To date, a large body of artist produced medical images continue to be used by medical students, such as images by Frank H. Netter, e.g. Cardiac images. However, a number of online anatomical models are becoming available.

A single patient X-ray is not a computer generated image, even if digitized. However, in applications which involve CT scans a three-dimensional model is automatically produced from many single-slice x-rays, producing "computer generated image". Applications involving magnetic resonance imaging also bring together a number of "snapshots" (in this case via magnetic pulses) to produce a composite, internal image.

In modern medical applications, patient-specific models are constructed in 'computer assisted surgery'. For instance, in total knee replacement, the construction of a detailed patient-specific model can be used to carefully plan the surgery. [9] These three-dimensional models are usually extracted from multiple CT scans of the appropriate parts of the patient's own anatomy. Such models can also be used for planning aortic valve implantations, one of the common procedures for treating heart disease. Given that the shape, diameter, and position of the coronary openings can vary greatly from patient to patient, the extraction (from CT scans) of a model that closely resembles a patient's valve anatomy can be highly beneficial in planning the procedure. [10]

Cloth and skin images

Computer-generated wet fur Wet Fur - CGI.jpg
Computer-generated wet fur

Models of cloth generally fall into three groups:

To date, making the clothing of a digital character automatically fold in a natural way remains a challenge for many animators. [12]

In addition to their use in film, advertising and other modes of public display, computer generated images of clothing are now routinely used by top fashion design firms. [13]

The challenge in rendering human skin images involves three levels of realism:

The finest visible features such as fine wrinkles and skin pores are the size of about 100 µm or 0.1 millimetres. Skin can be modeled as a 7-dimensional bidirectional texture function (BTF) or a collection of bidirectional scattering distribution function (BSDF) over the target's surfaces.

Interactive simulation and visualization

Interactive visualization is the rendering of data that may vary dynamically and allowing a user to view the data from multiple perspectives. The applications areas may vary significantly, ranging from the visualization of the flow patterns in fluid dynamics to specific computer aided design applications. [15] The data rendered may correspond to specific visual scenes that change as the user interacts with the system — e.g. simulators, such as flight simulators, make extensive use of CGI techniques for representing the world. [16]

At the abstract level, an interactive visualization process involves a "data pipeline" in which the raw data is managed and filtered to a form that makes it suitable for rendering. This is often called the "visualization data". The visualization data is then mapped to a "visualization representation" that can be fed to a rendering system. This is usually called a "renderable representation". This representation is then rendered as a displayable image. [16] As the user interacts with the system (e.g. by using joystick controls to change their position within the virtual world) the raw data is fed through the pipeline to create a new rendered image, often making real-time computational efficiency a key consideration in such applications. [16] [17]

Computer animation

Machinima films are, by nature, CGI films

While computer-generated images of landscapes may be static, computer animation only applies to dynamic images that resemble a movie. However, in general, the term computer animation refers to dynamic images that do not allow user interaction, and the term virtual world is used for the interactive animated environments.

Computer animation is essentially a digital successor to the art of stop motion animation of 3D models and frame-by-frame animation of 2D illustrations. Computer generated animations are more controllable than other more physically based processes, such as constructing miniatures for effects shots or hiring extras for crowd scenes, and because it allows the creation of images that would not be feasible using any other technology. It can also allow a single graphic artist to produce such content without the use of actors, expensive set pieces, or props.

To create the illusion of movement, an image is displayed on the computer screen and repeatedly replaced by a new image which is similar to the previous image, but advanced slightly in the time domain (usually at a rate of 24 or 30 frames/second). This technique is identical to how the illusion of movement is achieved with television and motion pictures.

Virtual worlds

A yellow submarine in Second Life Yellow Submarine Second Life.png
A yellow submarine in Second Life
Metallic balls Metallic balls.png
Metallic balls

A virtual world is a simulated environment, which allows the user to interact with animated characters, or interact with other users through the use of animated characters known as avatars. Virtual worlds are intended for its users to inhabit and interact, and the term today has become largely synonymous with interactive 3D virtual environments, where the users take the form of avatars visible to others graphically. [18] These avatars are usually depicted as textual, two-dimensional, or three-dimensional graphical representations, although other forms are possible [19] (auditory [20] and touch sensations for example). Some, but not all, virtual worlds allow for multiple users.

In courtrooms

Computer-generated imagery has been used in courtrooms, primarily since the early 2000s. However, some experts have argued that it is prejudicial. They are used to help judges or the jury to better visualize the sequence of events, evidence or hypothesis. [21] However, a 1997 study showed that people are poor intuitive physicists and easily influenced by computer generated images. [22] Thus it is important that jurors and other legal decision-makers be made aware that such exhibits are merely a representation of one potential sequence of events.

Motion capture

Computer-generated imagery is often used in conjunction with motion capture to better cover the faults that come with CGI and animation. Computer-generated imagery is limited in its practical application by how realistic it can look. Unrealistic, or badly managed computer-generated imagery can result in the Uncanny Valley effect. [23] This effect refers to the human ability to recognize things that look eerily like humans, but are slightly off. Such ability is a fault with normal computer-generated imagery which, due to the complex anatomy of the human body, can often fail to replicate it perfectly. This is where motion capture comes into play. Artists can use a motion capture rig to get footage of a human performing an action and then replicate it perfectly with computer-generated imagery so that it looks normal.

The lack of anatomically correct digital models contributes to the necessity of motion capture as it is used with computer-generated imagery. Because computer-generated imagery reflects only the outside, or skin, of the object being rendered, it fails to capture the infinitesimally small interactions between interlocking muscle groups used in fine motor control, like speaking. The constant motion of the face as it makes sounds with shaped lips and tongue movement, along with the facial expressions that go along with speaking are difficult to replicate by hand. [24] Motion capture can catch the underlying movement of facial muscles and better replicate the visual that goes along with the audio, like Josh Brolin's Thanos.

See also

Related Research Articles

Computer animation Art of creating moving images using computers

Computer animation is the process used for digitally generating animated images. The more general term computer-generated imagery (CGI) encompasses both static scenes and dynamic images, while computer animation only refers to moving images. Modern computer animation usually uses 3D computer graphics to generate a two-dimensional picture, although 2D computer graphics are still used for stylistic, low bandwidth, and faster real-time renderings. Sometimes, the target of the animation is the computer itself, but sometimes film as well.

Digital art Collective term for art that is generated digitally with a computer

Digital art is an artistic work or practice that uses digital technology as part of the creative or presentation process. Since the 1960s, various names have been used to describe the process, including computer art and multimedia art. Digital art is itself placed under the larger umbrella term new media art.

Autodesk 3ds Max, formerly 3D Studio and 3D Studio Max, is a professional 3D computer graphics program for making 3D animations, models, games and images. It is developed and produced by Autodesk Media and Entertainment. It has modeling capabilities and a flexible plugin architecture and must be used on the Microsoft Windows platform. It is frequently used by video game developers, many TV commercial studios, and architectural visualization studios. It is also used for movie effects and movie pre-visualization. For its modeling and animation tools, the latest version of 3ds Max also features shaders, dynamic simulation, particle systems, radiosity, normal map creation and rendering, global illumination, a customizable user interface, new icons, and its own scripting language.

Visual effects is the process by which imagery is created or manipulated outside the context of a live action shot in filmmaking. The integration of live action footage and CG elements to create realistic imagery is called VFX.

Scientific visualization Field of computer graphics concerned with presenting scientific data visually

Scientific visualization is an interdisciplinary branch of science concerned with the visualization of scientific phenomena. It is also considered a subset of computer graphics, a branch of computer science. The purpose of scientific visualization is to graphically illustrate scientific data to enable scientists to understand, illustrate, and glean insight from their data.

Visualization (graphics) set of techniques for creating images, diagrams, or animations to communicate a message

Visualization or visualisation is any technique for creating images, diagrams, or animations to communicate a message. Visualization through visual imagery has been an effective way to communicate both abstract and concrete ideas since the dawn of humanity. Examples from history include cave paintings, Egyptian hieroglyphs, Greek geometry, and Leonardo da Vinci's revolutionary methods of technical drawing for engineering and scientific purposes.

Non-photorealistic rendering

Non-photorealistic rendering (NPR) is an area of computer graphics that focuses on enabling a wide variety of expressive styles for digital art, in contrast to traditional computer graphics, which focuses on photorealism. NPR is inspired by other artistic modes such as painting, drawing, technical illustration, and animated cartoons. NPR has appeared in movies and video games in the form of cel-shaded animation as well as in scientific visualization, architectural illustration and experimental animation.

Real-time computer graphics term

Real-time computer graphics or real-time rendering is the sub-field of computer graphics focused on producing and analyzing images in real time. The term can refer to anything from rendering an application's graphical user interface (GUI) to real-time image analysis, but is most often used in reference to interactive 3D computer graphics, typically using a graphics processing unit (GPU). One example of this concept is a video game that rapidly renders changing 3D environments to produce an illusion of motion.

Graphic art software software category

Graphic art software is a subclass of application software used for graphic design, multimedia development, stylized image development, technical illustration, general image editing, or simply to access graphic files. Art software uses either raster or vector graphic reading and editing methods to create, edit, and view art.

Virtual cinematography set of cinematographic techniques performed in a computer graphics environment

Virtual cinematography is the set of cinematographic techniques performed in a computer graphics environment. It includes a wide variety of subjects like photographing real objects, often with stereo or multi-camera setup, for the purpose of recreating them as three-dimensional objects and algorithms for the automated creation of real and simulated camera angles. Virtual cinematography can be used to shoot scenes from otherwise impossible camera angles, create the photography of animated films, and manipulate the appearance of computer-generated effects.

3D rendering process of converting 3D models into 2D images on a computer

3D rendering is the 3D computer graphics process of converting 3D models into 2D images on a computer. 3D renders may include photorealistic effects or non-photorealistic styles.

3D computer graphics Graphics that use a three-dimensional representation of geometric data

3D computer graphics, or three-dimensional 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. The resulting images may be stored for viewing later or displayed in real time. Unlike 3D film and similar techniques, the result is two-dimensional, without the illusion of being solid.

A projection augmented model is an element sometimes employed in virtual reality systems. It consists of a physical three-dimensional model onto which a computer image is projected to create a realistic looking object. Importantly, the physical model is the same geometric shape as the object that the PA model depicts.

Computer graphics (computer science) Sub-field of computer science

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 the study of three-dimensional computer graphics, it also encompasses two-dimensional graphics and image processing.

Computer graphics Graphics created using computers

Computer graphics is the branch of computer science that deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized applications. A great deal of specialized hardware and software has been developed, with the displays of most devices being driven by computer graphics hardware. It is a vast and recently developed area of computer science. The phrase was coined in 1960 by computer graphics researchers Verne Hudson and William Fetter of Boeing. It is often abbreviated as CG, or typically in the context of film as computer generated imagery (CGI).

Fractal-generating software

Fractal-generating software is any type of graphics software that generates images of fractals. There are many fractal generating programs available, both free and commercial. Mobile apps are available to play or tinker with fractals. Some programmers create fractal software for themselves because of the novelty and because of the challenge in understanding the related mathematics. The generation of fractals has led to some very large problems for pure mathematics.

The history of computer animation began as early as the 1940s and 1950s, when people began to experiment with computer graphics - most notably by John Whitney. It was only by the early 1960s when digital computers had become widely established, that new avenues for innovative computer graphics blossomed. Initially, uses were mainly for scientific, engineering and other research purposes, but artistic experimentation began to make its appearance by the mid-1960s. By the mid-1970s, many such efforts were beginning to enter into public media. Much computer graphics at this time involved 2-dimensional imagery, though increasingly as computer power improved, efforts to achieve 3-dimensional realism became the emphasis. By the late 1980s, photo-realistic 3D was beginning to appear in film movies, and by mid-1990s had developed to the point where 3D animation could be used for entire feature film production.

A medical animation is a short educational film, usually based around a physiological or surgical topic, that is rendered using 3D computer graphics. While it may be intended for an array of audiences, the medical animation is most commonly utilized as an instructional tool for medical professionals or their patients.

Visual computing is a generic term for all computer science disciplines handling with images and 3D models, i.e. computer graphics, image processing, visualization, computer vision, virtual and augmented reality, video processing, but also includes aspects of pattern recognition, human computer interaction, machine learning and digital libraries. The core challenges are the acquisition, processing, analysis and rendering of visual information. Application areas include industrial quality control, medical image processing and visualization, surveying, robotics, multimedia systems, virtual heritage, special effects in movies and television, and computer games.

References

Citations

  1. 1 2 3 Peitgen 2004, pp. 462–466.
  2. Game programming gems 2 by Mark A. DeLoura 2001 ISBN   1-58450-054-9 page 240
  3. Digital modeling of material appearance by Julie Dorsey, Holly Rushmeier, François X. Sillion 2007 ISBN   0-12-221181-2 page 217
  4. Sondermann 2008, pp. 8–15.
  5. Interactive environments with open-source software: 3D walkthroughs by Wolfgang Höhl, Wolfgang Höhl 2008 ISBN   3-211-79169-8 pages 24-29
  6. Advances in Computer and Information Sciences and Engineering by Tarek Sobh 2008 ISBN   1-4020-8740-3 pages 136-139
  7. Encyclopedia of Multimedia Technology and Networking, Volume 1 by Margherita Pagani 2005 ISBN   1-59140-561-0 page 1027
  8. Interac storytelling: First Joint International Conference by Ulrike Spierling, Nicolas Szilas 2008 ISBN   3-540-89424-1 pages 114-118
  9. Total Knee Arthroplasty by Johan Bellemans, Michael D. Ries, Jan M.K. Victor 2005 ISBN   3-540-20242-0 pages 241-245
  10. I. Waechter et al. Patient Specific Models for Minimally Invasive Aortic Valve Implantation in Medical Image Computing and Computer-Assisted Intervention -- MICCAI 2010 edited by Tianzi Jiang, 2010 ISBN   3-642-15704-1 pages 526-560
  11. Cloth modeling and animation by Donald House, David E. Breen 2000 ISBN   1-56881-090-3 page 20
  12. Film and photography by Ian Graham 2003 ISBN   0-237-52626-3 page 21
  13. Designing clothes: culture and organization of the fashion industry by Veronica Manlow 2007 ISBN   0-7658-0398-4 page 213
  14. Handbook of Virtual Humans by Nadia Magnenat-Thalmann and Daniel Thalmann, 2004 ISBN   0-470-02316-3 pages 353-370
  15. Mathematical optimization in computer graphics and vision by Luiz Velho, Paulo Cezar Pinto Carvalho 2008 ISBN   0-12-715951-7 page 177
  16. 1 2 3 GPU-based interactive visualization techniques by Daniel Weiskopf 2006 ISBN   3-540-33262-6 pages 1-8
  17. Trends in interactive visualization by Elena van Zudilova-Seinstra, Tony Adriaansen, Robert Liere 2008 ISBN   1-84800-268-8 pages 1-7
  18. Cook, A.D. (2009). A case study of the manifestations and significance of social presence in a multi-user virtual environment. MEd Thesis. Available online
  19. Biocca & Levy 1995, pp. 40–44.
  20. Begault 1994, p. 212.
  21. Computer-generated images influence trial results The Conversation, 31 October 2013
  22. Kassin, S. M. (1997). "Computer-animated Display and the Jury: Facilitative and Prejudicial Effects". Law and Human Behavior. 40 (3): 269–281. doi:10.1023/a:1024838715221.
  23. Palomäki, Jussi; Kunnari, Anton; Drosinou, Marianna; Koverola, Mika; Lehtonen, Noora; Halonen, Juho; Repo, Marko; Laakasuo, Michael (2018-11-01). "Evaluating the replicability of the uncanny valley effect". Heliyon. 4 (11): e00939. doi: 10.1016/j.heliyon.2018.e00939 . ISSN   2405-8440. PMID   30519654.
  24. Pelachaud, Catherine; Steedman, Mark; Badler, Norman (1991-06-01). "Linguistic Issues in Facial Animation". Center for Human Modeling and Simulation.

Sources

  • Begault, Durand R. (1994). 3-D Sound for Virtual Reality and Multimedia. AP Professional. ISBN   978-0-1208-4735-8.CS1 maint: ref=harv (link)
  • Biocca, Frank; Levy, Mark R. (1995). Communication in the Age of Virtual Reality. Lawrence Erlbaum Associates. ISBN   978-0-8058-1549-8.CS1 maint: ref=harv (link)
  • Peitgen, Heinz-Otto; Jürgens, Hartmut; Saupe, Dietmar (2004). Chaos and Fractals: New Frontiers of Science. Springer Science & Business Media. ISBN   978-0-387-20229-7.
  • Sondermann, Horst (2008). Light Shadow Space: Architectural Rendering with Cinema 4D. Vienna: Springer. ISBN   978-3-211-48761-7.CS1 maint: ref=harv (link)