High-resolution data-driven models of Daylight Redirection Components

Daylight Redirecting Components (DRCs) guide daylight to zones with insufficient daylight exposure. They reduce energy demand for lighting, heating and cooling, and improve visual and thermal comfort. The data-driven model in Radiance is a means to model DRCs in daylight simulation. Rather than internal optical mechanisms, their resulting Bidirectional Scattering Distribution Function (BSDF) is replicated.We present models of two DRCs that are generated from measurements.

The impact of the following three necessary steps in the generation of data-driven models from measured BSDF shall be evaluated:

1) interpolation between measurements at sparse sets of incident directions;
2) extrapolation for directions that cannot be measured;
3) application of a directional basis of given directional resolution.

It is shown that data-driven models can provide a realistic representation of both DRCs. The sensitivity to effects from interpolation differs for the two DRCs due to the varying complexity of their BSDFs. Due to the irregularity of the measured BSDFs, extrapolation is not reliable and fails for both tested DRCs. Different measurement and modeling protocols should be applied to different class systems, rather than aiming at a common low-resolution discretization.