Résumé
Computer graphics lighting is the collection of techniques used to simulate light in computer graphics scenes. While lighting techniques offer flexibility in the level of detail and functionality available, they also operate at different levels of computational demand and complexity. Graphics artists can choose from a variety of light sources, models, shading techniques, and effects to suit the needs of each application. Light sources allow for different ways to introduce light into graphics scenes. Point sources emit light from a single point in all directions, with the intensity of the light decreasing with distance. An example of a point source is a standalone light bulb. A directional source (or distant source) uniformly lights a scene from one direction. Unlike a point source, the intensity of light produced by a directional source does not change with distance over the scale of the scene, as the directional source is treated as though it is extremely far away. An example of a directional source is sunlight on Earth. A spotlight produces a directed cone of light. The light becomes more intense as the viewer gets closer to the spotlight source and to the center of the light cone. An example of a spotlight is a flashlight. Area lights are 3D objects which emit light. Whereas point lights and spot lights sources are considered infinitesimally small points, area lights are treated as physical shapes. Area light produce softer shadows and more realistic lighting than point lights and spot lights. Ambient light sources illuminate objects even when no other light source is present. The intensity of ambient light is independent of direction, distance, and other objects, meaning the effect is completely uniform throughout the scene. This source ensures that objects are visible even in complete darkness. A lightwarp is a technique of which an object in the geometrical world refracts light based on the direction and intensity of the light. The light is then warped using an ambient diffuse term with a range of the color spectrum.
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