Light and Skin Interactions

3.1. Global Light Transport

In order to render the image of a scene or object, we need to compute the radiance values at selected points. This process involves the solution of an integral equation describing light transfer in the environment of interest. This integral light transport equation, also known as the rendering equation in computer graphics [136], can be expressed in different forms, depending on the application field. For consistency with the graphics literature, we will express it in terms of radiances on the basis of the ray law (the radiance is constant along a line of sight between objects [225]), and the definition of the bidirectional scattering distribution function (BDF) (Section 2.6.2). In a simplified form, it is given ...