Rendering or image synthesis is the process of generating a photorealistic or non-photorealistic image from a 2D or 3D model by means of a computer program. The resulting image is referred to as the render. Multiple models can be defined in a scene file containing objects in a strictly defined language or data structure. The scene file contains geometry, viewpoint, texture, lighting, and shading information describing the virtual scene. The data contained in the scene file is then passed to a rendering program to be processed and output to a digital image or raster graphics image file. The term "rendering" is analogous to the concept of an artist's impression of a scene. The term "rendering" is also used to describe the process of calculating effects in a video editing program to produce the final video output.
Global illumination (GI), or indirect illumination, is a group of algorithms used in 3D computer graphics that are meant to add more realistic lighting to 3D scenes. Such algorithms take into account not only the light that comes directly from a light source, but also subsequent cases in which light rays from the same source are reflected by other surfaces in the scene, whether reflective or not.
In 3D computer graphics, radiosity is an application of the finite element method to solving the rendering equation for scenes with surfaces that reflect light diffusely. Unlike rendering methods that use Monte Carlo algorithms, which handle all types of light paths, typical radiosity only account for paths which leave a light source and are reflected diffusely some number of times before hitting the eye. Radiosity is a global illumination algorithm in the sense that the illumination arriving on a surface comes not just directly from the light sources, but also from other surfaces reflecting light. Radiosity is viewpoint independent, which increases the calculations involved, but makes them useful for all viewpoints.
In computer graphics, photon mapping is a two-pass global illumination rendering algorithm developed by Henrik Wann Jensen between 1995 and 2001 that approximately solves the rendering equation for integrating light radiance at a given point in space. Rays from the light source and rays from the camera are traced independently until some termination criterion is met, then they are connected in a second step to produce a radiance value. The algorithm is used to realistically simulate the interaction of light with different types of objects. Specifically, it is capable of simulating the refraction of light through a transparent substance such as glass or water, diffuse interreflection between illuminated objects, the subsurface scattering of light in translucent materials, and some of the effects caused by particulate matter such as smoke or water vapor. Photon mapping can also be extended to more accurate simulations of light, such as spectral rendering. Progressive photon mapping (PPM) starts with ray tracing and then adds more and more photon mapping passes to provide a progressively more accurate render.
The Utah teapot, or the Newell teapot, is a 3D test model that has become a standard reference object and an in-joke within the computer graphics community. It is a mathematical model of an ordinary Melitta-brand teapot that appears solid with a nearly rotationally symmetrical body. Using a teapot model is considered the 3D equivalent of a "Hello, World!" program, a way to create an easy 3D scene with a somewhat complex model acting as the basic geometry for a scene with a light setup. Some programming libraries, such as the OpenGL Utility Toolkit, even have functions dedicated to drawing teapots.
Shading refers to the depiction of depth perception in 3D models or illustrations by varying the level of darkness. Shading tries to approximate local behavior of light on the object's surface and is not to be confused with techniques of adding shadows, such as shadow mapping or shadow volumes, which fall under global behavior of light.
The Stanford bunny is a computer graphics 3D test model developed by Greg Turk and Marc Levoy in 1994 at Stanford University. The model consists of 69,451 triangles, with the data determined by 3D scanning a ceramic figurine of a rabbit. This figurine and others were scanned to test methods of range scanning physical objects.
Greg Turk is an American-born researcher in the field of computer graphics and a professor at the School of Interactive Computing in the College of Computing at the Georgia Institute of Technology. His paper "Zippered polygon meshes from range images", concerning the reconstruction of surfaces from point data, brought the "Stanford bunny", a frequently used example object in computer graphics research, into the CGI lexicon. Turk actually purchased the original Stanford Bunny and performed the initial scans on it. He is also known for his work on simplification of surfaces, and on reaction–diffusion-based texture synthesis. In 2008, Turk was the technical papers chair of SIGGRAPH 2008. In 2012, Greg Turk was awarded the ACM Computer Graphics Achievement Award 2012.
The bidirectional reflectance distribution function is a function of four real variables that defines how light is reflected at an opaque surface. It is employed in the optics of real-world light, in computer graphics algorithms, and in computer vision algorithms. The function takes an incoming light direction, , and outgoing direction, , and returns the ratio of reflected radiance exiting along to the irradiance incident on the surface from direction . Each direction is itself parameterized by azimuth angle and zenith angle , therefore the BRDF as a whole is a function of 4 variables. The BRDF has units sr−1, with steradians (sr) being a unit of solid angle.
Path-tracing is a computer graphics Monte Carlo method of rendering images of three-dimensional scenes such that the global illumination is faithful to reality. Fundamentally, the algorithm is integrating over all the illuminance arriving to a single point on the surface of an object. This illuminance is then reduced by a surface reflectance function (BRDF) to determine how much of it will go towards the viewpoint camera. This integration procedure is repeated for every pixel in the output image. When combined with physically accurate models of surfaces, accurate models of real light sources, and optically correct cameras, path tracing can produce still images that are indistinguishable from photographs.
In computer graphics, per-pixel lighting refers to any technique for lighting an image or scene that calculates illumination for each pixel on a rendered image. This is in contrast to other popular methods of lighting such as vertex lighting, which calculates illumination at each vertex of a 3D model and then interpolates the resulting values over the model's faces to calculate the final per-pixel color values.
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.
Marc Levoy is a computer graphics researcher and Professor Emeritus of Computer Science and Electrical Engineering at Stanford University, a vice president and Fellow at Adobe Inc., and a Distinguished Engineer at Google. He is noted for pioneering work in volume rendering, light fields, and computational photography.
Computer graphics lighting is the collection of techniques used to simulate light in computer graphics scenes. While lighting techniques offer flexibility in the level of detail and functionality available, they also operate at different levels of computational demand and complexity. Graphics artists can choose from a variety of light sources, models, shading techniques, and effects to suit the needs of each application.
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. The individuals who serve as professional designers for computers graphics are known as "Graphics Programmers", who often are computer programmers with skills in computer graphics design.
In 3D computer graphics, 3D modeling is the process of developing a mathematical coordinate-based representation of any surface of an object in three dimensions via specialized software by manipulating edges, vertices, and polygons in a simulated 3D space.
This is a glossary of terms relating to computer graphics.
Michael F. Cohen is an American computer scientist and researcher in computer graphics. He was a senior research scientist at Microsoft Research for 21 years until he joined Facebook Research in 2015. In 1998, he received the ACM SIGGRAPH CG Achievement Award for his work in developing radiosity methods for realistic image synthesis. He was elected a Fellow of the Association for Computing Machinery in 2007 for his "contributions to computer graphics and computer vision." In 2019, he received the ACM SIGGRAPH Steven A. Coons Award for Outstanding Creative Contributions to Computer Graphics for “his groundbreaking work in numerous areas of research—radiosity, motion simulation & editing, light field rendering, matting & compositing, and computational photography”.
Sutherland's Volkswagen, or the Utah VW Bug, is a 3D model. It is a mathematical model of a 1967 Volkswagen Beetle and one of the earliest 3D computer models, aside from Catmull's hand.
