[esp-r] again about Radiance

[Gian Luca Brunetti]

Dear list,
I am writing again about the ESP-r Radiance interaction.

I August while away from my computer I optimistically posted a couple of 
messages here in which I reasoned about the possibility to modify the 
insolation values in the .shda files taking into account the illuminance 
values produced by Radiance at each time step. (This by using a ratio of 
the illuminance levels calculated with solar obstruction as black bodies 
and the illuminance levels calculated with their true reflectances.)

Now inspecting the interface to Radiance in ESP-r, which I only 
previously used for daylight factors calculations, I have seen that in 
the interactive set-up is a menu entry for the ESP-r - Radiance coupling 
and another for the calculation of daylight coefficient.

I also saw the 1998 article  by Clarke and Janak "Simulating the Thermal 
Effects of Daylight-controlled Lighting" (Building Performance, 1998).

About the coupling mode, I think I have understood that it comes close 
to my needs to take into account the effect of reflections by external 
obstructions; but also that this operation only obviously regards just 
illuminance levels, without effect on solar gains.

And about the daylight coefficient calculations, I think I have 
understood that each set of them belongs to a specific position in time.

It doesn't help my understanding that I am not able to run the two 
operations, nor the one, nor the other. (Incidenlty, I also have not 
been able to run the operations to obtain glare evaluations, which I 
presently am not longing for.)

I imagine that there must be some Radiance files to write or modify to 
place sensors at surfaces or else, but I have no clue about where to 
start; and I also most fundamentally suspect that I am not on the right 
track at a more general level.
 
That said, running the two above described operations has just 
indirectly to do with present aim, and might be not essential for me. My 
priority is to find a way to extract grids of illuminance levels for 
each opaque internal surface from the  rendering operations, to obtain 
the mean illuminance levels for each of them. (Morevoer, relative 
differences of illuminance from surface to surface would be enough for 
my needs - I woun't necessarily need absolute values; and relative 
values might even be inferred from to-be-rendered colors.)  But the 
Radiance rendering options I have seen produce graphical results, not 
textual.

About all this, I poke in the source of the Radiance's file "dayfact", 
which is there presented as being able to calculate daylight factors and 
illuminance levels, but I haven't found no clue about the calculation or 
set up needed to request illuminance levels.

Does anybody using Radiance here have a suggestion about how to obtain 
the mean illuminance level for a certain surface in a certain position 
in time?

I fear that if I can't perform this most basic operation I'll have to 
throw in the towel.

Thank you in advance.

Best regards

Gian Luca Brunetti

Politecnico di Milano
Dipartimento BEST
via Bonardi 11
20133 Milano
tel./fax 02 2399 5750