Computer graphics (computer science): Difference between revisions

Revision as of 00:49, 17 February 2021

Revision as of 01:02, 17 February 2021

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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 representation]]s are most commonly used. Two dimensional [[Surface (topology)|surface]]s are a good representation for most objects, though they may be non-[[manifold]]. Since surfaces are not finite, discrete digital approximations are used. [[polygon mesh|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).<ref>{{cite web |url = http://graphics.ethz.ch/events/pbg/07/ |title=Point Based Graphics 2007 - PBG07 |website = Graphics.ethz.ch |access-date=2014-05-01}}</ref> 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 set]]s have been developed into a useful representation for deforming surfaces which undergo many topological changes (with [[fluids]] being the most notable example).<ref name="stanford fedkiw">{{cite web |url = http://graphics.stanford.edu/~fedkiw/ |title = Ron Fedkiw |website = graphics.stanford.edu |access-date=2014-05-01 }}</ref>

; Geometry Subfieldssubfields include:

* [[Implicit surface]] modeling – an older subfield which examines the use of algebraic surfaces, [[constructive solid geometry]], etc., for surface representation.

* Digital geometry processing – [[3d scanning|surface reconstruction]], simplification, fairing, mesh repair, [[mesh parameterization|parameterization]], remeshing, [[mesh generation]], surface compression, and surface editing all fall under this heading.<ref name="caltech multires dgp">[http://www.multires.caltech.edu/pubs/DGPCourse/ ] {{webarchive |url = https://web.archive.org/web/20070214021951/http://www.multires.caltech.edu/pubs/DGPCourse/ |date=February 14, 2007 }}</ref><ref name="uiuc graphics dgp">[http://graphics.cs.uiuc.edu/~garland/class/geometry/ CS 598: Digital Geometry Processing (Fall 2004)<!-- Bot generated title -->] {{webarchive|url=https://archive.is/20041025104252/http://graphics.cs.uiuc.edu/~garland/class/geometry/ |date=2004-10-25 }}</ref><ref name="ubc sheffa dgp">{{cite web|url=http://www.cs.ubc.ca/~sheffa/dgp/ |title=Digital Geometry Processing |website = cs.ubc.ca |access-date=2014-05-01}}</ref>

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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.

Animation subfields include:

; Subfields

* [[Motion capture|Performance capture]]

* Character animation

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Rendering generates images from a model. Rendering may simulate [[light transport theory|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.

Rendering subfields include:

; Transport

* [[light transport theory|Transport]] describes how illumination in a scene gets from one place to another. [[visibility (geometry)|Visibility]] is a major component of light transport.

The* formerScattering: problemModels refers toof ''[[scattering]],'' i.e.,(how light interacts with the relationshipsurface between''at incominga given point'') and outgoing''[[shading]]'' illumination(how atmaterial properties vary across the surface) are used to describe the appearance of a givensurface. point In graphics these problems are often studied within the context of rendering since they can substantially affect the design of [[rendering algorithm]]s. 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.)

; Scattering

Models of ''scattering'' and ''shading'' are used to describe the appearance of a surface. In graphics these problems are often studied within the context of rendering since they can substantially affect the design of [[rendering algorithm]]s. Shading can be broken down into two orthogonal issues, which are often studied independently:

# '''scattering''' – how light interacts with the surface ''at a given point''

# '''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.)

;Other subfields

* [[Non-photorealistic rendering]]

* [[Physically based rendering]] – concerned with generating images according to the laws of [[geometric optics]]