Download CS335 Graphics and Multimedia: Understanding Illumination, Shading, and Light Transport - and more Study notes Computer Science in PDF only on Docsity! CS335 Graphics and Multimedia Fall 2009 Simulate of the light transport • Illumination - the transport of luminous flux from light sources between points via direct and indirect paths • Lighting - the process of computing the luminous intensity reflected from a specified 3-D point • Shading - the process of assigning a colors to a pixels x L I C k ’ • Only the direct illumination from the emitters to the reflectors of the scene • Ignore the geometry of light emitters, and consider only the geometry of reflectors • most of the light from a scene results from a single bounce of a emitted ray off of a reflective surface • Why??? Graphics Hacks • No spatial or directional characteristics • The amount of ambient light incident on each object is a constant for all surfaces in the scene. • An ambient light can have a color. • The amount of ambient light that is reflected by an object is independent of the object's position or orientation. • Surface properties are used to determine how much ambient light is reflected. Ambient Light Source diffusekk IkI ambient ambientambientreflected , • All of the rays from a directional light source have the same direction, and no point of origin. • It is as if the light source was infinitely far away from the surface that it is illuminating. • Example: Directional Light Sources • An ideal diffuse surface is, at the microscopic level, a very rough surface. • Because of the microscopic variations in the surface, an incoming ray of light is equally likely to be reflected in any direction over the hemisphere. • Diffuse reflections are constant over each surface in a scene, independent of the viewing direction. Ideal Diffuse Reflection • An ideal diffuse surface is also called Lambertian Lambert's Cosine Law • Its brightness proportional to the cosine of the angle between reflector’s surface normal and incident light rays • Independent of angle between observer and reflector Computing Diffuse Reflection • kd: the reflector’s diffuse reflectance • Ilight: the intensity of the incident light • Some objects are microscopically smooth, but not perfectly so • These objects appear glossy: Non-ideal Specular Reflectors • Not based on physical theory • But easy to compute and obtains visually pleasing results Phong Illumination Model for Specular Reflection • Ambient Reflection • Diffuse Reflection • Specular Reflection Summary of 3 Illumination Models
