[Radiance-general] Randance and different sky descriptions

[Rob Guglielmetti]

Hi Allison,

Nice to see you on the list! So what you have here is two different ways of specifying the sky. The first form ("Software 1"), the gensky command is given inline (hence the '!' that precedes the gensky command), and the STDOUT (which contains the skyfunc and the sun source description) are then passed on to the celestial hemisphere sky and ground primitives. In the second form, that STDOUT is explicitly listed in the sky description. If you simply try the "Software 1" sky description's gensky command at the command line, you get:

command:
gensky 3 21 12.01 +s -a 40.03 -o 105.28 -m 105.00

output (STDOUT):
# gensky 3 21 12.01 +s -a 40.03 -o 105.28 -m 105.00
# Local solar time: 11.87
# Solar altitude and azimuth: 49.5 -3.1
# Ground ambient level: 15.0

void light solar
0
0
3 6.88e+06 6.88e+06 6.88e+06

solar source sun
0
0
4 0.034560 -0.648139 0.760737 0.5

void brightfunc skyfunc
2 skybr skybright.cal
0
7 1 1.09e+01 2.30e+01 6.50e-01 0.034560 -0.648139 0.760737


You can see that these sections bear a resemblance to the first sections in your "Software 2" sky description in format, but not in value(s). Again, these are the bits that define the luminous sky and ground hemispheres, as well as the position and intensity of the sun. So clearly the Software 2 gensky input is different from the Software 1 gensky input. I can't back out what Software 2's gensky input must have looked like, although I'm sure a few people on this list may be able to. THe bigger issue is we need to know some more details about your test case, and the relative differences in the reported values from one software tool to the next. It would also be helpful to know what tools you are using, and how you are using them, rather than just trying to reverse engineer the inputs. 

- Rob



 

On Feb 26, 2013, at 5:31 PM, Allison Bygott <Allison.Bygott at megroup.com> wrote:

> Hello.
>  
> I have been evaluating a couple of different software programs that interface with Radiance. Unfortunately, my "standard" test models aren't producing the same results in each software; the results are different by at least a factor of 2. I'm trying to understand how each software is separately using Radiance to come up with daylight results. I believe this requires an understanding of how the sky files are generated. I spent some time today poking around the Radiance-online mailing lists, looking for sky file content clues, but I suspect that some of these concepts are above me. I did review the gensky document dated 4/24/98 and I found it informative. I'm hoping that the community might provide some insight on the content of two "comparable" sky files; please see below:
>  
> Software 1:
>  
> !gensky 3 21 12.01 +s -a 40.03 -o 105.28 -m 105.00
>  
> skyfunc glow skyglow
> 0
> 0
> 4  0.7  0.8  1.0 0
>  
> skyglow source sky
> 0
> 0
> 4 0 0 1 180
>  
> skyfunc glow grndglow
> 0
> 0
> 4 0.05 0.1 0.07 0
>  
> grndglow source ground
> 0
> 0
> 4 0 0 -1 180
>  
>  
>  
> Software 2:
>  
> void light solar
> 0
> 0
> 3 11009526.873677 11009526.873677 11009526.873677
>  
> solar source sun
> 0
> 0
> 4 0.039983 -0.647611 0.760921 0.5
>  
> void brightfunc skyfunc
> 2 skybr IES_skybright.cal
> 0
> 7 1 15.092265 18.041592 0.649859 0.039983 -0.647611 0.760921
>  
> skyfunc glow skyglow
> 0
> 0
> 4 0.989 0.989 1.159 0
>  
> skyglow source sky
> 0
> 0
> 4 0.0 0.0 1.0 180
>  
> skyfunc glow groundglow
> 0
> 0
> 4 1.0 1.0 1.0 0
>  
> groundglow source ground
> 0
> 0
> 4 0.0 0.0 -1.0 180
>  
>  
> Thank you. I appreciate any thoughts on the matter.
>  
> <image002.png>
> 
> ALLISON BYGOTT, PE, LC, LEED-AP
> ENGINEER
> t: 303.382.1920 x4132
> www.megroup.com
> <image004.jpg><image006.jpg>
>  
>  
> 
> 
> CONFIDENTIALITY NOTICE: This e-mail and any attached file(s) are intended only for the use of the individual or entity to whom or to which it is addressed and may contain information that is privileged, confidential, proprietary, and trade secret. If the reader of this message is not the intended recipient or an employee or agent responsible for delivering the message to the intended recipient, you are hereby notified that any dissemination, distribution, or reproduction of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately and discard the original message and any attachment(s).
> _______________________________________________
> Radiance-general mailing list
> Radiance-general at radiance-online.org
> http://www.radiance-online.org/mailman/listinfo/radiance-general