[Radiance-general] Approximating the gross daylight flux thro ugh venetian blinds.

[Greg Ward]

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.

-Greg

> From: "Reinhart, Christoph" <Christoph.Reinhart at nrc-cnrc.gc.ca>
> 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
> condition?
>
> Christoph