Subfields Of Computer Graphics

Geometry

Geometry studies the representation of three-dimensional objects in a discrete digital setting. Because the appearance of an object depends largely on the exterior of the object, boundary representations are most common in computer graphics. Two dimensional surfaces are a good analogy for the objects most often used in graphics, though quite often these objects are non-manifold. Since surfaces are not finite, a discrete digital approximation is required: polygonal meshes (and to a lesser extent subdivision surfaces) are by far the most common representation, although point-based representations have been gaining some popularity in recent years. These representations are Lagrangian, meaning the spatial locations of the samples are independent. In recent years, however, 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).

Subfields Of Geometry

• 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

Animation studies descriptions for surfaces (and other phenomena) that move or deform over time. Historically most interest in this area has been focused on parametric and data-driven models, but in recent years physical simulation has experienced a renaissance due to the growing computational capacity of modern machines.

Subfields Of Animation

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

Rendering

Rendering converts a model into an image either by simulating light transport to get physically-based photorealistic images, or by applying some kind of style as in non-photorealistic rendering. The two basic operations in realistic rendering are:

• Transport (how much light gets from one place to another) and
• Scattering (how surfaces interact with light).

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.
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

• Physically-based rendering - concerned with generating images according to the laws of geometric optics.
• Real time rendering - focuses on rendering for interactive applications, typically using specialized hardware like GPUs.
• Non-photorealistic rendering
• Relighting - recent area concerned with quickly re-rendering scenes.