dgleeson's profile - activity

I think IES support have already been in touch directly, but for the benefit of anyone else reading this: BSDFs are curr

Leaving aside the impact of coincident surfaces which has already been answered, are you sure these surfaces were actual

Thanks Greg, makes perfect sense. Cheers!

When modelling a ground plane as a defined piece of geometry, with a surface reflectance of 20% and a ground reflectance value of -g 0.2 set in gensky I get a discrepancy between the luminance from my phyically modelled ground plane and the groundglow provided by gensky for two of the available sky types generated by gensky:

• Intermediate sky without sun (-i)
• Sunny sky without sun (-s)

For the other sky types, the luminance from my physically modelled ground is identical to that from the groundglow, such that the boundary between the physical ground plane and the groundglow is seamless. For the two sky types mentioned above there is a clear discrepancy, with the ground glow brighter than the modelled ground. I have checked the gensky manual and it includes the following:

Average ground reflectance is rfl. This value is used to compute skyfunc when Dz is negative. Ground plane brightness is the same for −s as for +s. (Likewise for −i and +i, but see the −r option below.)

Further, searching the mailing list yields the following comment from Greg Ward when a user encountered the same thing: http://www.radiance-online.org/piperm...

The glow computed for the ground includes whatever sunlight should be
falling on it. An intermediate sky has some sun, so the solar
irradiance (-R) setting has an effect. (Even if you use -i or -s, gensky still computes the ground radiance based on the sun being out
-- it just leaves off the solar source.)

-Greg

So I understand it is doing what it's supposed to do, my question is why? For what practical purposes is it desirable for the ground glow for these two sky types to be calculated differently from the other sky types? It results in a visible boundary between the modelled ground plane and the groundglow in rendered images.

Thanks Mostapha, I'll take a look at gendaymtx and give the mailing list a shot. I'll report back here if I have any success.

Hi,

I've been experimenting with gencumulativesky and the -S1/-S2 switches to chose between the "smeared" representation of the sun and the "binned" representation of the sun. The version of gencumulativesky I have has a -r switch which the help text tells me divides the output by 179000 to convert from (I think) W/sr.m² to kWh/m².

The issue I have is that this does not appear to be applied to the SunFile.rad file which is generated as a result of chosing the binned option. Thus when I generate an image using the sky and sun output from gencumulativesky I get really big numbers (W/sr.m²).

I've experimented with feeding my image into pcomb and setting the -s factor to be 1/179000 (5.587e-6) and this appears to convert my numbers into the right ball park for kWh/m².

However I'm not entirely sure that what I've done is actually numerically correct. Does anyone have any guidance on the correct way to work with gencumulativesky with the binned suns and produce output in kWh/m²?