Lighting Models

Abstract

This chapter presents the basics for illumination in computer graphics. A distinction is made between local and global illumination models. In a modelled computer graphics scene, the light from modelled light sources hits the surface of objects, is reflected there and creates lighting effects depending on the material properties of the object surfaces. The Phong model is presented as an important representative of local illumination models. Furthermore, this chapter contains explanations of shading methods that determine how the polygons of the object surfaces are coloured on the basis of the lighting calculation. In a three-dimensional scene, not only objects are illuminated by light sources, resulting in certain (local) effects. In addition, some of the light is reflected from the surfaces of the objects, which in turn illuminates other objects. These interactions are modelled by global illumination models. The radiosity model can be used to model global diffuse reflections. Ray tracing methods are suitable for simulating global specular reflections. This chapter contains the basics of these two methods.