抄録
The Monte Carlo method, which has recently been widely used to predict the illuminance distribution of a room arranged in a complicated way with furniture, is an easier algorithm than others and is suited to simulating the various states of lighting in a room. The accuracy of the illuminance distribution calculation is affected by the number of particles that substitute for the luminous flux of the light source and by the number of elements of the room surfaces. Therefore, we investigated the optimal number of the particles and elements considering the CPU time and error rate of the illuminance calculation when a shadow caster assumed to be a worker's head was set at an arbitrary position in a rectangular parallel-piped model room. A new method, which uses the incident particles on the surrounding elements of the calculation point, was developed to decrease the CPU time and calculation error. We examined various reflectances of the room surfaces, positions and diameters of the shadow caster. As a result, using only 1/10 the CPU time of previous methods, we found that the optimal number of particles is five million and the optimal number of elements each surface of a room is 40×40 to 60×60.
