3D graphics

3D computer graphics, or “3D graphics,” sometimes called CGI, 3D-CGI or three-dimensional computer graphics are graphics that use a three-dimensional representation of geometric data (often Cartesian) that is stored in the computer for the purposes of performing calculations and rendering digital images, usually 2D images but sometimes 3D images. The resulting images may be stored for viewing later (possibly as an animation) or displayed in real time.

3D computer graphics, contrary to what the name suggests, are most often displayed on two-dimensional displays. Unlike 3D film and similar techniques, the result is two-dimensional, without visual depth. More often, 3D graphics are being displayed on 3D displays, like in virtual reality systems.

3D graphics stand in contrast to 2D computer graphics which typically use completely different methods and formats for creation and rendering.

3D computer graphics rely on many of the same algorithms as 2D computer vector graphics in the wire-frame model and 2D computer raster graphics in the final rendered display. In computer graphics software, 2D applications may use 3D techniques to achieve effects such as lighting, and similarly, 3D may use some 2D rendering techniques.

The objects in 3D computer graphics are often referred to as 3D models. Unlike the rendered image, a model's data is contained within a graphical data file. A 3D model is a mathematical representation of ''any'' three-dimensional object; a model is not technically a ''graphic'' until it is displayed. A model can be displayed visually as a two-dimensional image through a process called 3D rendering, or it can be used in non-graphical computer simulations and calculations. With 3D printing, models are rendered into an actual 3D physical representation of themselves, with some limitations as to how accurately the physical model can match the virtual model.

History

William Fetter was credited with coining the term ''computer graphics'' in 1961 to describe his work at Boeing. One of the first displays of computer animation was ''Futureworld'' (1976), which included an animation of a human face and a hand that had originally appeared in the 1971 experimental short '' A Computer Animated Hand'', created by University of Utah students Edwin Catmull and Fred Parke.

3D computer graphics software began appearing for home computers in the late 1970s. The earliest known example is '' 3D Art Graphics'', a set of 3D computer graphics effects, written by Kazumasa Mitazawa and released in June 1978 for the Apple II.

Overview

3D computer graphics production workflow falls into three basic phases:
# 3D modeling – the process of forming a computer model of an object's shape
# Layout and CGI animation – the placement and movement of objects (models, lights etc.) within a scene
# 3D rendering – the computer calculations that, based on light placement, surface types, and other qualities, generate (rasterize the scene into) an image

Modeling

The model describes the process of forming the shape of an object. The two most common sources of 3D models are those that an artist or engineer originates on the computer with some kind of 3D modeling tool, and models scanned into a computer from real-world objects (Polygonal Modeling, Patch Modeling and NURBS Modeling are some popular tools used in 3d modeling). Models can also be produced procedurally or via physical simulation. Basically, a 3D model is formed from points called vertices that define the shape and form polygons. A polygon is an area formed from at least three vertices (a triangle). A polygon of n points is an n-gon. The overall integrity of the model and its suitability to use in animation depend on the structure of the polygons.

Layout and animation

Before rendering into an image, objects must be laid out in a scene. This defines spatial relationships between objects, including location and size. Animation refers to the temporal description of an object (i.e., how it moves and deforms over time. Popular methods include keyframing, inverse kinematics, and motion capture). These techniques are often used in combination. As with animation, physical simulation also specifies motion.

Materials and textures

Materials and textures are properties that the render engine uses to render the model. One can give the model materials to tell the render engine how to treat light when it hits the surface. Textures are used to give the material color using a color or albedo map, or give the surface features using a bump map or normal map. It can be also used to deform the model itself using a displacement map.

Rendering

Rendering converts a model into an image either by simulating light transport to get photo-realistic images, or by applying an art 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). This step is usually performed using 3D computer graphics software or a 3D graphics API. Altering the scene into a suitable form for rendering also involves 3D projection, which displays a three-dimensional image in two dimensions. Although 3D modeling and CAD software may perform 3D rendering as well (e.g., Autodesk 3ds Max or Blender), exclusive 3D rendering software also exists (e.g., OTOY's Octane Rendering Engine, Maxon's Redshift)
3D rendering