Sky luminance: Standard digital form for modelling

Abstract

The luminance distribution of the sky dome provides basic information for various modelling tasks, including daylighting analysis and design, and for the creation of ultra-realistic computer-generated visualisations. To date there have been few tools to support the development and adoption of realistic luminance models for worldwide use. This paper presents a new approach to modelling sky luminance where explicit attention is paid to the presence of clouds and other obstructions to light available from the sky. A standard digital form (SDF) is proposed as a way of providing consistent representations of data from various sources (measured or empirical) that allows the data to be manipulated using a standard and consistent set of basic operators. These operators can be applied to build new (hybrid) models which can then be made available for use in simulation packages. Access to the SDF models is achieved through a standard set of functions which can be integrated into other user-written software.