The term 3D computer graphics in particular refers to works of graphic art that were created with the aid of digital computers and specialized 3D software. In general, the term may also refer to the process of creating such graphics, or the field of study of 3D computer graphic techniques and its related technology.
3D computer graphics are distinct from 2D computer graphics in that a three-dimensional virtual representation of objects is stored in the computer for the purposes of performing calculations. In general, the art of 3D graphics is akin to sculpting or photography, while the art of 2D graphics is analogous to painting. In computer graphics software, this distinction is occasionally blurred; some 2D applications use 3D techniques to achieve certain effects such as lighting, while some primarily 3D applications make use of 2D visual techniques.
Creation of 3D computer graphics
The process of creating 3D computer graphics can be chronologically divided into three basic phases:
- Modelling
- Scene layout setup
- Rendering
Modelling
The modelling stage could be described as shaping individual objects that are later used in the scene. There exist a number of modelling techniques; Constructive Solid Geometry, NURBS modelling and polygonal modelling are good examples. Modelling processes may also include editing object surface or material properties (e.g. color, luminosity, diffuse and specular shading components - more commonly called roughness and shininess, reflection characteristics, transparency or opacity, or index of refraction), adding textures, bump-maps and other features.
Modelling may also include various activities related to preparing a 3D model for animation. Objects may be fitted with a skeleton, a central framework of an object with the capability of affecting the shape or movements of that object. This aids in the process of animation, in that the movement of the skeleton will automatically affect the corresponding portions of the model. See also Forward kinematic animation and Inverse kinematic animation.
Modelling can be performed by a means of a dedicated program (e.g. Lightwave Modeler, Rhinoceros 3D, Moray), an application component (Shaper, Lofter in 3D Studio) or some scene description language (as in POV-Ray). In some cases, there is no strict distinction between these phases and modelling is just part of the scene creation process (for example, this is true in case of Caligari trueSpace).
Scene layout setup
Scene setup involves arranging objects, lights, cameras and other entities on a scene which will later be used to produce a still image or an animation. If used for animation, this phase usually makes use of a technique called "keyframing", which facilitates creation of complicated movement in the scene. With the aid of keyframing, instead of having to fix an object's position, rotation, or scaling for each frame in an animation, one only has to set up some key frames between which states in every frame are interpolated.
Lighting is an important aspect of scene setup. As is the case in real-world scene arrangement, lighting is a significant contributing factor to the resultant aesthetic and visual quality of the finished work. As such, it can be a difficult art to master. Lighting effects can contribute greatly to the mood and emotional response affected by a scene, a fact which is well-known to photographers and theatrical lighting technicians.
Rendering
Rendering is the final process of creating the actual 2D image or an animation from the prepared scene. This can be compared to taking a photo or filming the scene after the setup is finished in real life. Photo-realistic image quality is often a desirable outcome, and to this end several different, and often specialized, rendering methods have been developed. These range from the evidently non-realistic wireframe rendering through polygon-based rendering, to more modern techniques such as: scanline rendering, raytracing or radiosity.
Rendering software may simulate such cinematographic effects as lens flares, depth of field or motion blur. These artifacts are, in reality, a by-product of the mechanical imperfections of physical photography, but as the human eye is accustomed to their presence, the simulation of such artifacts can lend an element of realism to a scene. Techniques have been developed for the purpose of simulating other naturally-occurring effects, such as the interaction of light with an atmosphere, smoke, or particulate matter. Examples of such techniques include particle systems (which can simulate rain, smoke, or fire), volumetric sampling (to simulate fog, dust and other spatial atmospheric effects), and caustics (to simulate light focusing by uneven light-refracting surfaces, such as the light ripples seen on the bottom of a swimming pool).
The rendering process is known to be computationally expensive, given the complex variety of physical processes being simulated. Computer processing power has increased rapidly over the years, allowing for a progressively higher degree of realistic rendering. Film studios that produce computer-generated animations typically make use of a render farm to generate images in a timely manner.
3D graphics software
- 3D Studio - probably one of the most popular 3d graphics packages of mid-90's which worked under MS-DOS. Later, it evolved into Win32 application 3D Studio Max, which is popular nowadays, among artists using Microsoft Windows based machines. Originally Autodesk product, it was later developed by Autodesk's division Kinetix. Later still Autodesk created a new division called Discreet (a merger of Kinetix and an acquired company called Discreet Logic) which is developing 3D Studio Max. Current version is 5 (as of late 2002).
- Newtek Lightwave 3D - originally developed for Amiga computers in early 1990's, it later evolved into an advanced and widely used 3d graphics and animation package, now available for Windows, Mac OS and Mac OS X. Current version is 7.5 (as of late 2002). It consists of two components: Modeler and Layout (scene editor).
- Caligari trueSpace - an integrated 3D graphics application with an intuitive interface. A distinctive feature of this application is that all phases of 3d graphics creation are performed within a single program. Not as advanced as leading packages in this domain but provides such features as physical phenomena simulation (e.g. wind, gravity, body collisions) out-of-the-box.
- POV-Ray - advanced free raytracing software. Uses its own scene description language with features like macros, loops and conditional statements. It's completely free albeit not released under GPL. Does not include a built-in modeler.
- Moray - modeler for POVRay.
- Rhinoceros 3D - a powerful NURBS modeller.
- Blender - a modeller and renderer with such features as support for scripting.
- BMRT - a free renderman compatible renderer which implements a subset of renderman API.
For other software, see also entries on CAD and rendering.