Approximating the gross daylight flux thro ugh venetian blinds.

Hi Christoph,

You can use mkillum or any other aspect of Radiance for an annual illuminance profile by creating a cumulative sky model from weather data. Using mkillum, you would pick up the appropriate external reflections as well, which a BRTDfunc could not do. If you want to break down the profile over time, then you need to create a time-stepped calculation, possibly using an acceleration scheme such as the one you devised or those of John Mardaljevic or Raphael Compagnon. In such cases, I can see where a BRTDfunc modeling blinds might be a real time-saver, since it will avoid a lot of the sampling variance caused by detailed blind geometry. It still wouldn't pick up those external reflections, though.



From: "Reinhart, Christoph" <>
Date: October 29, 2004 9:10:21 AM PDT

Greg, I think that it would be REALLY useful for daylight-coefficient-based
daylight simulations if someone (meaning you:)) came up with a BRTDFunc for
blinds. This way one could simulate interior annual illuminance profiles
with the blinds opened and closed. This is already possible if one simulates
the blinds geometrically in gory detail (genblind), but the simulation times
are horrendous. I assume the calculation time penalty would be less severe
if one used "BRTDFunc" instead? To my knowledge, mkillum cannot be used
with a daylight coefficient approach since mkillum is tied to a specific sky