dear @chris, the IES LM-83-23 recommend for the sDA calculation, to use 6 ambient bounces (ab) and a ambient division parameter value of 1000.
Can I ask why for the Annual Daylight, the “High Quality” in the Radiance parameter component, the ad is set to 25000?
According the setting Radiance Options, the max value for the ad is set to 4096
a value of ad= 25000 significantly improves the result.
I was interested in understanding whether the value he had set had an underlying motivation.
In general, questions that are about Radiance parameters are probably better answered on the Radiance forum. Or they could be answered by someone with more Radiance experience than me like @mikkel. (I’m not sure why you referenced me in your post).
I imagine that our use of high -ad values might have to do with how you can (optionally) model the direct sun accurately using an Improved DC strategy in Honeybee:
That is what the enhanced_ option is for on the HB Annual Daylight component.
The LM-83 standard has historically accepted results like what you see for DAYSIM there, where the hourly direct sun is modeled coarsely with sky patches. So it’s all wrong if you look at it on an hour-by-hour basis but I guess maybe things are kinda OK if you look at annual metrics over the whole year. For reasons like this, most Radiance experts would probably agree that LM-83 is not the best standard if you’re really trying to understand daylight quality. But we also recognize that it’s the standard that we’re all stuck with modeling for LEED.
In summary you probably don’t need such high ad values when you’re just trying to satisfy LM-83. But, again, I am not the best person to answer here.
after the update of the LM 83-12 to the last edition, the LM 83-23, there is no longer any reference regarding the imput parameter of the ambient bounce and ambient division, but the LEED v4.1 refers to the 2012 version.
Dear @mikkel
for more LEED certification, I was asked to specify which radiance parameters I used, this is why I asking if there was a reason and/or a source/research why did you default to an -ad of 25,000 for a high quality annual simulation.
When using rcontrib/rfluxmtx I would never go so low on the ambient divisions unless I just want a quick check to see if the results are somewhat reasonable.
Like the sarith research in the “Radiance Image Parameters”, he used as default 1 rays per sky patches (-c 1) for the sampling parameters, and then a maximum of -c 9 (for this example) to improve the quality.
Regarding this parameter, I noticed that this is not used for the rpict (image-based view) simulation, instead it is an important parameter for the research from sarith.
