Conference Year



Blinds, Shading, Daylighting, Ray-tracing, Radiosity


This paper presents a hybrid ray-tracing and radiosity method for processing luminous flux in spaces equipped with venetian blinds. The method considers both diffuse and specular characteristics of blinds and aims to establish a balance between computational speed and accuracy. Specular components are treated using ray-tracing techniques using a shining factor for the blinds to split between directly and diffusely reflected components. The direct components are traced inside the blind cavity and inside the room while the direct-diffuse components inside the blind cavity are processed in a two-dimensional radiosity calculation until the final diffuse flux departing the cavity is determined. Diffuse-to-diffuse transmission is considered using a traditional radiosity method. Each room surface is divided into sub-surfaces and given an initial luminous exitance, after accounting for directly traced portions. Then a 3-D radiosity method is employed for the entire room to compute illuminance distributions on each subsurface and on the work plane. The developed model will help in the estimation of daylight distributions in spaces with venetian blinds and potential lighting energy savings calculations if combined with electric lighting controls. It will also lead to development of new control algorithms for shading and lighting systems for perimeter spaces with controllable shading devices.