Rendering or image synthesis is the method in which shading, color and lamination to a 2D or 3D model by means of computer programs.
Rendering process is very much helpful in showing interactive as well as non-interactive architecture, video games, simulators, TV visual effects, films and designing visualization. There are a wide variety of renderers available, some are integrated into modeling and animation software packages, some are stand-alone and others are open source softwares.
3D graphics, rendering is done slowly, as in pre-rendering, or in real time. When the wireframe sketch is ready, rendering is used over it, which adds various elements such as bitmap textures, procedural textures, lights, bump mapping and relative position. The result is a completed image as per the user's expectation.
Rendering for games and simulations, where the user's interaction is involved. This is calculated and displayed, at rates of approx. 20 to 120 frames/sec. In real-time rendering, the goal is to show as much information as possible as the eye can process in a fraction of a second.
2D and 3D Animations for media in which user interaction is not involved, such as feature films and video, are rendered comparatively slower. For complex scenes, the Rendering times for individual frames varies from a few seconds to several days. It works in this way, rendered frames are initially stored on a hard disk. After that the files can be transferred to other media such as motion picture film or optical disk. These frames are then displayed sequentially at high frame rates, like 24, 25, or 30 frames per second, in order to achieve the illusion of movement.
The rendering process becomes more expensive, when it demands the complex simulation. Using compositing software, other extra layers can be added and a final shot is made ready.