Algorithm of Lighting Simulation(<Special Issue>Prospect of Lighting Simulation Program)

Abstract

Recently, much more lighting simulation tools or 3DCAD/CG tools implement algorithms for lighting environment simulation. However, some users of these tools do not understand how the algorithms work and, consequently, they do not know appropriate algorithm for a certain case study. To simulate lighting environment taking into account interreflection, boundary condition of architectural space or light flux must be considered discretely to keep computational load finite. In this article, author try to describe brief explanation of radiosity method, which transacts continuous boundary condition discretely, and raytracing method, which transacts infinite light flux discretely, so that even beginners of numeric calculation can comprehend both algorithms intuitively. At first, principle of interreflection calculation is explained with simple case with 2 elements. Then, calculation method of incident luminous flux ratio from another element is described. Finally, advantageous points and disadvantageous points of both algorithms are explained with various example figures of calculation result.