On the Computation of Equivalent Sphere Illumination

Equivalent sphere illumination (ESI) can be calculated by an efficient technique that will make computation for many target locations in a room practical. The technique can be easily coded into a computer program, and results will be provided much faster that programs based on other computational techniques. Computations for the background and task luminance of a target are separated into two components: Part I of this paper considers the calculation of the direct components (the Appendices give a specific algorithm for their computation); Part II considers the computation of the reflected components.