3D model
From Wikipedia, the free encyclopedia
In 3D computer graphics, a 3D model is a mathematical representation of any three-dimensional object (either inanimate or living). It can be displayed as a two-dimensional image through a process called 3D rendering or used in a computer simulation of physical phenomena.
3D models are most often created with special software applications called 3D modelers. Being a collection of data (points and other information), 3D models can be created by hand or algorithmically (procedural modeling). Though they most often exist virtually (on a computer or a file on disk), even a description of such a model on paper can be considered a 3D model.
3D models are widely used anywhere 3D graphics are used. Actually, their use predates the widespread use of 3D graphics on personal computers. Many computer games used pre-rendered images of 3D models as sprites before computers could render them in real-time.
Today, 3D models are used in a wide variety of fields. The medical industry uses detailed models of organs. The movie industry uses them as characters and objects for animated and real-life motion pictures. The video game industry uses them as assets for computer and video games. The science sector uses them as highly detailed models of chemical compounds. The architecture industry uses them to demonstrate proposed buildings and landscapes. The engineering community uses them as designs of new devices, vehicles and structures as well as a host of other uses. In recent decades the earth science community has started to construct 3D geological models as a standard practice.
A 3D model by itself is not visual. It can be rendered as a simple wireframe model at varying levels of detail, or mathematically shaded in a variety of ways. It is usually desirable to add color to a model's surface in a user controlled way prior to rendering. Most 3D modeling software allows the user to color the model's vertices, and that color is then interpolated across the model's surface during rendering. This is often how models are colored by the modeling software while the model is being created. The most common method of adding color information to a 3D model is by applying a 2D texture image to the model's surface through a process called texture mapping. Texture images are no different than any other digital image, but during the texture mapping process, special pieces of information (called texture coordinates or UV coordinates) are added to the model that indicate which parts of the texture image map to which parts of the 3D model's surface. Textures allow 3D models to look significantly more detailed and realistic than they would otherwise.
Other effects, beyond texturing, can be done to 3D models to add to their realism. For example, the surface normals can be tweaked to affect how they are lit, certain surfaces can have bump mapping applied and any other number of 3D rendering tricks can be applied.
3D models are often animated for some uses. For example, 3D models are heavily animated for use in feature films and video games. They can be animated from within the 3D modeler that created them or externally. Often extra data is added to the model to make it easier to animate. For example, some 3D models of humans and animals have entire bone systems so they will look realistic when they move and can be manipulated via joints and bones.
[edit] 3D model market
There is a large and thriving market for 3D models (as well as 3D-related content, such as textures, scripts, etc.), either as individual models or large collections. Online marketplaces for 3D content allow individual artists to sell content that they have created. Often, the artists' goal is to get additional value out of assets they have previously created for projects. By doing so, artists can earn more money out of their old content, and companies can save money by buying pre-made models instead of paying an employee to create one from scratch. These marketplaces typically split the sale between themselves and the artist that created the asset, often in a roughly 50-50 split. In most cases, the artist retains ownership of the 3d model; the customer only buys the right to use and present the model.
