3D Rendering for Real-time and video
Rendering is the final process of creating the actual 2D image or animation from the prepared scene. This can be compared to taking a photo or filming a scene after the setup is finished in real life. Several different, and often specialized, rendering methods have been developed. These range from the distinctly non-realistic wireframe rendering through polygon-based rendering, to more advanced techniques such as: scanline rendering, ray tracing, radiosity, and gobal illumination. Rendering may take from seconds to days for a single image/frame. In general, different methods are better suited for either photo-realistic rendering, or real-time rendering.
Rendering for interactive media, such as games and simulations, is calculated and displayed in real time, at rates of approximately 20 to 120 frames per second. In real-time rendering, the goal is to show as much information as possible as the eye can process in a 30th of a second, or 30 frames per second, which is the standard frame rate for video. The goal of real time rendering is primarily speed and not photo-realism. In fact, here exploitations are made in the way the eye ‘perceives’ the world, and as a result the final image presented is not necessarily that of the real-world, but one close enough for the human eye to tolerate. Rendering software may simulate such visual effects as lens flares, depth of field or motion blur. These are attempts to simulate visual phenomena resulting from the optical characteristics of cameras and of the human eye. These effects can lend an element of realism to a scene, even if the effect is merely a simulated artifact of a camera. This is the basic method employed in interactive video games. The rapid increase in computer processing power has allowed a progressively higher degree of realism for real-time rendering, including techniques such as HDR rendering. Real-time rendering is often polygonal and aided by the computer’s graphic processor unit.
Animations for non-interactive media, such as feature films and video, are rendered much more slowly. Non-real time rendering enables the leveraging of limited processing power in order to obtain higher image quality. Rendering times for individual frames may vary from a few seconds to several days for complex scenes. Rendered frames are stored on a hard disk then can be transferred to other media such as motion picture film or optical disk. These frames are then displayed sequentially at high frame rates, typically 30 frames per second, to achieve the illusion of movement.
When the goal is photo-realism, techniques are employed such as radiosity or global illumination. This is the basic method employed in 3d architecure visualization, product visualization and video cinematics and motion pictures. Techniques have been developed for the purpose of simulating other naturally-occurring effects, such as the interaction of light with various forms of matter.
The rendering process is 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 render farms to generate images in a timely manner. Directors like Michael Bay are increasingly utilizing 3D film making and animation technologies in an effort to advance the usage and content rate of this remarkable technology. However, falling hardware costs mean that it is entirely possible to create small amounts of 3D animation on a home computer system. The output of the renderer is often used as only one small part of a completed motion-picture scene. Many layers of material may be rendered separately and integrated into the final shot using video editing compositing software.
