Computer Graphics

Computer graphics

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.

Overview

The term Computer graphics has multiple meaning:

• Field of science, which studies the manipulation of visual and geometric information using computational techniques. Computer graphics as an academic discipline focuses on the mathematical and computational foundations of image generation and processing rather than purely aesthetic issues.
• The economic branch which deals with the creating and modification of an image on a screen.
• The images created or manipulated in two or three dimensions (2D or 3D respectively), see 2D computer graphics and 3D computer graphics.

Computer graphics is often differentiated from the field of visualization, although the two fields have many similarities.

Applications of Computer graphics are:

• Digital art
• Special effects
• Visual effects
• Video games

Connected studies of Computer graphics are:

• Computer vision
• Image processing
• Computational Geometry
• Computational Topology

History

One of the first displays of computer animation was Futureworld (1976), which included an animation of a human face and hand � produced by Ed Catmull and Fred Parke at the University of Utah.

There are several international conferences and journals where the most significant results in computer graphics are published. Among them are the SIGGRAPH and Eurographics conferences and the Association for Computing Machinery (ACM) Transactions on Graphics journal. The joint Eurographics and ACM SIGGRAPH symposium series features the major venues for the more specialized sub-fields: Symposium on Geometry Processing,Symposium on Rendering, and Symposium on Computer Animation. As in the rest of computer science, conference publications in computer graphics are generally more significant than journal publications (and subsequently have lower acceptance rates).

Subfields in computer graphics

A broad classification of major subfields in computer graphics might be:

1. Geometry: studies ways to represent and process surfaces
2. Animation: studies with ways to represent and manipulate motion
3. Rendering: studies algorithms to reproduce light transport
4. Imaging: studies image acquisition or image editing

Geometry

The subfield of geometry studies the representation of three-dimensional objects in a discrete digital setting. Because the appearance of an object depends largely on its exterior, boundary representations are most commonly used. Two dimensional surfaces are a good representation for most objects, though they may be non-manifold. Since surfaces are not finite, discrete digital approximations are used. Polygonal meshes (and to a lesser extent subdivision surfaces) are by far the most common representation, although point-based representations have become more popular recently (see for instance the Symposium on Point-Based Graphics). These representations are Lagrangian, meaning the spatial locations of the samples are independent. Recently, Eulerian surface descriptions (i.e., where spatial samples are fixed) such as level sets have been developed into a useful representation for deforming surfaces which undergo many topological changes (with fluids being the most notable example).

Geometry Subfields

• Constructive solid geometry - Process by which complicated objects are modelled with implicit geometric objects and boolean operations
• Discrete differential geometry - a nascent field which defines geometric quantities for the discrete surfaces used in computer graphics.
• Digital geometry processing - surface reconstruction, simplification, fairing, mesh repair, parameterization, remeshing, mesh generation, surface compression, and surface editing all fall under this heading.
• Point-based graphics - a recent field which focuses on points as the fundamental representation of surfaces.
• Subdivision surfaces
• Out-of-core mesh processing - another recent field which focuses on mesh datasets that do not fit in main memory.

Animation

The subfield of animation studies descriptions for surfaces (and other phenomena) that move or deform over time. Historically, most work in this field has focused on parametric and data-driven models, but recently physical simulation has become more popular as computers have become more powerful computationally.

Subfields

• Performance capture
• Character animation
• Physical simulation (e.g. cloth modeling, animation of fluid dynamics, etc.)

Rendering

Rendering generates images from a model. Rendering may simulate light transport to create realistic images or it may create images that have a particular artistic style in non-photorealistic rendering. The two basic operations in realistic rendering are transport (how much light passes from one place to another) and scattering (how surfaces interact with light). See Rendering (computer graphics) for more information.

Transport

Transport describes how illumination in a scene gets from one place to another. Visibility is a major component of light transport.

Scattering

Models of scattering and shading are used to describe the appearance of a surface. Although these issues may seem like problems all on their own, they are studied almost exclusively within the context of rendering.^{[citation needed]} Shading can be broken down into two orthogonal issues, which are often studied independently:

1. scattering - how light interacts with the surface at a given point
2. shading - how material properties vary across the surface

The former problem refers to scattering, i.e., the relationship between incoming and outgoing illumination at a given point. Descriptions of scattering are usually given in terms of a bidirectional scattering distribution function or BSDF. The latter issue addresses how different types of scattering are distributed across the surface (i.e., which scattering function applies where). Descriptions of this kind are typically expressed with a program called a shader. (Note that there is some confusion since the word "shader" is sometimes used for programs that describe local geometric variation.)