[Radiance-general] Re: Tregenza Sky and Daylight Coefficients

[Greg Ward]

Hi Chris,

I keep hoping I'll get around to making this more automatic.  The  
current distribution of Radiance has a file called "tregenza.cal"  
included in the ray/src/cal/cal/ directory, which converts a sky  
direction into a Tregenza bin number for rtcontrib.  There is another  
file called "tregsrc.cal" in the same directory that is used to  
generate Tregenza solar and sky positions, and a file called  
"tregsamp.dat" in the ray/lib directory that has 64 randomly  
distributed samples over each Tregenza patch, plus 64 randomly  
distributed samples over the ground (negative altitude angles).  This  
file is useful in combination with rtrace to determine the patch  
contributions for a particular sky/ground model.

I have some scripts as well for using these files, but they are  
complicated and specific to projects I've done in the past, and not  
generally usable or understandable.  I wish I could provide you with  
more, but that's all I have at the moment.

Best,
-Greg

> From: Christian Humann <chris at coolshadow.com>
> Date: January 7, 2009 8:31:31 AM PST
>
> Greetings and Happy New Year to all!
>
> Can anyone point me in the right direction for finding examples and  
> related papers on using / creating a Tregenza sky for calculating  
> Daylight Coefficients?  I've been using Daysim and am trying to  
> scratch my head around what exactly it's doing in the background.   
> My understanding so far is that Daysim uses a modified Rtrace  
> routine, and I'm interested in how the more recent Rtcontrib can be  
> used in its place. Thanks.
>
> Chris H
> Berkeley, CA USA