Three-dimensional models are often generated using specialized software such as 3D modeling tools, but they can also be generated using other methods. As a collection of points and other information, a 3D model can be generated by hand or according to certain algorithms. Although they usually exist virtually on a computer or in a computer file, similar models depicted on paper can also be considered 3D models. Three-dimensional models are widely used wherever three-dimensional graphics are used. In fact, their use predates the popularity of 3D graphics on personal computers. Many computer games use pre-rendered 3D model images as sprites for real-time computer rendering.
Nowadays, 3-D models are used in a variety of different fields. They are used in the medical industry to create accurate models of organs; in the film industry for moving characters, objects, and realistic movies; in the video game industry as a resource in computer and video games; in the scientific field as accurate models of chemical compounds; in the architectural industry to display proposed buildings or representations of landscapes; in the engineering community to design new equipment, vehicles, structures, and other applications; and in more recent decades in the field of 3D models. Engineering uses them to design new equipment, vehicles, structures, and other applications; and in recent decades, the earth sciences have begun to build 3D geological models.
The 3D models themselves are invisible and can be rendered at different levels of detail or shaded in different ways based on simple wireframes. However, many 3D models are overlaid with textures, and the process of arranging textures onto a 3D model is called texture mapping. A texture is an image, but it makes the model more detailed and realistic looking. For example, a 3D model of a person with textured skin and clothing looks more realistic than a simple monochromatic model or a wireframe model.
Besides textures, other effects can be used to add realism to a 3D model. For example, the normals of surfaces can be adjusted to illuminate them, and some surfaces can be texture-mapped using convex-concave texture mapping and other stereoscopic rendering techniques.