[Radiance-general] RE: DF calculated in Radiance and Relux

[Thomas Bleicher]

On 31 Mar 2008, at 10:46, Per Haugaard wrote:

> Dear Thomas and other Radiance users,
>
> Thank you very much for your reply. I used the following rtrace  
> command instead:
> rtrace -w -h -I+ -ab 6 -aa 0.1 -ad 1026 -as 256 -ar 512  
> DF_OfficeLL.oct < DFcoordinates.inp | rcalc -e '$1=($1*0.265+ 
> $2*0.670+$3*0.065)*179/10000*100' > OfficeLL.log
>
> which reduced the calculated DF in radiance to pretty much match  
> the ones calculated in Relux.
Still doesn't explain why a very high '-ab' value results in a DF  
that doesn't look right.

I always thought that Radiance would produce more accurate results  
the longer it runs.

> Then I changed the transmittance for the glazing from 0,72 to 0,58  
> and made a new octree
> and re-calculated the DFs. I here after used the above rtrace command.
> However, this had no influence on the calculated DF at all.

Without knowing the geometry it's hard to say. If your windows are  
the only openings
you should see a reduction in the DF. It's also possible that your  
window polygons are
not where you expect them to be. If you're on a Unix system you can  
use rvu to get
a visual impression of the room and with the 't' keystroke you can  
trace a ray to it's
intersection with the geometry. It tells you which polygon and  
material you've hit.
You can use it to verify your material changes are now part of the  
new octree.

Under Windows you can render a picture to control that the windows  
are in place.
To get an equivalent of the 't' you could use rtrace with a carefully  
selected origin and
direction and a modified output option.
> I have also tried to alter the '-ad', '-as' and the '-ar' with  
> limit results.
These options will only have an effect if your geometry is very  
detailed and you
might miss a window with the initial '-ad' setting. Given the window  
polygons
below I'd say you have a few very large windows, so you don't have to  
change
these values.


Hth,
Thomas
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