Rendering

Rendering is the process of producing bitmapped images from a view of 3-D models in a 3-D scene. It is, in effect, "taking a picture" of the scene. An animation is a series of such renderings, each with the scene slightly changed.

A camera is placed at a location in a 3-D coordinate space, pointing in a given direction. Those polygons that fall within the camera's field of view are mathematically projected onto a plane, just as a real camera projects an image onto film. The rendering process necessarily involves some means of determining whether a given surface of a model is obscured by another surface closer to the camera.

Once it is determined what surfaces are visible to the camera, and where they project to on the viewing plane, the color of each pixel must be determined. Depending on the sophistication of the process in a given case, this result is the combination of the surface properties assigned to the object (color, shininess, etc.) and the lighting placed in the scene.

As an animation requires as many as 30 renderings for every second, rendering time is an extremely important consideration in all 3-D animation. Rendering time is a function not only of the power of the computer used, but also of the number of polygons in the scene, the complexity of the lighting, and the presence of computationally-intensive elements such as transparency and reflective surfaces.

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