MONTE-CARLO METHODS IN GLOBAL ILLUMINATION

lightsources, such as point or directional lightsources are preferred here, since their radiance is a Dirac-delta like function, which simplifies the integral of equation (2.50) to a sum. These methods take into account only a single reflection of the light coming from the abstract lightsources. Ideal mirrors and refracting objects cannot be rendered with these methods. 2. Recursive ray-tracing Another alternative is to eliminate from the rendering equation those energy contributions which cause the difficulties, and thus give ourselves a simpler problem to solve. For example, if limited level, say n, coupling caused by ideal reflection and refraction were allowed, and we were to ignore the other non-ideal components coming from non-abstract lightsources, then the number of surface points which would need to be evaluated to calculate a pixel color can be kept under control. Since the illumination formula contains two terms regarding the coherent components (reflective and refracting l...