published in 2007 in Proceedings of the International Building Performance Simulation Association (IBPSA) 2007 Conference
The directionality of light is defined as the balance between the diffuse and directional components of light within an environment. It is an indicator about the spatial distribution of light flow onto an element or into a space. This paper presents a new luminance based metric that quantifies the directionality of light. The diffuse and directional components of the luminous environment are isolated as a unique feature of simulation-based approach. The rationale and methodology of the directional-to-diffuse ratio is discussed through visual demonstrations and quantified metrics.