[Radiance-general] comparing RTRACE vs DAYSIM Daylight Coefficients

[Andrew McNeil]

Hi German,
Sorry to have taken so long to respond. When I first read your email I
didn't have time to dig in and planned to come back to it. Then I promptly
forgot about it.

The one thing that stands out, and could be a major source of error for a
clear sky is the ground reflectance. You're using 70% in the rtraced model,
but you aren't using it in the 5-phase method. Though if you have large-ish
local ground plane defined in scene.rad (which you always should, but even
the best of us sometimes leave out) this will be less of a problem.

You can specify ground reflectance in gendaymtx with the -g argument. The
default is -g 0.2 0.2 0.2 (which is a lot different from 70%). You
gendaymtx command would look something like this:
gendaymtx -h -g 0.7 0.7 0.7 -m 1 Santiago.wea > full_sky.skv

Let me know if this doesn't improve things and I'll dig in further.

Andy


On Tue, Sep 9, 2014 at 8:41 AM, CHI-German Molina <gmolina at hdlao.com> wrote:

> Dear All,
>
> I have been trying to replicate the "DAYSIM Daylight Coefficients",
> comparing those results with the RTRACE output. I am doing this following
> the 5 phase method tutorial, but I have not been succesful yet. Any
> comments would be great! I am not sure I am doing this well...
>
> So, what I did is to separate the whole scene (including overhangs) from
> the window.
>
> *FILE CONTENT*
>
> ##White.sky
> void glow skymat
> 0
> 0
> 4    1     1     1    0
>
> skymat source skysource
> 0
> 0
> 4     0    0    1    360
>
>
> ## suns.rad
> void light solar 0 0 3 1e6 1e6 1e6
> solar source sun 0 0 4 0 0.999 0.018 0.018 0.533
> .....
> lots of them.
>
> ## black.rad
> void plastic black
> 0
> 0
> 5 0 0 0 0 0
>
> ##clear.sky
> !gendaylit 3 1 9.5 -W 756 189 -g 0.7 -a -33.38 -o 70.78     ##There is a
> big ground with 70% reflectance
>
> skyfunc glow skyglow
> 0
> 0
> 4   1   1   1   0
>
> skyglow source skysource
> 0
> 0
> 4   0    0    1    360
>
>
> ##Santiago.wea
> place SANTIAGO_CHL
> latitude -33.38
> longitude 70.78
> time_zone 60
> site_elevation 476.0
> weather_data_file_units 1
> 1 1 9.5 756 189
>
>
>
>
>
> *RTRACE CALCULATIONS*
> oconv Materials/* scene.rad clear.sky windows.rad > clear_octree.oct
> cat Workplanes/WP.pts | rtrace -n 4 -I -ab 8 -ad 50000 -lw 2e-5 -dc 1 -dt
> 0 -dj 0 -st 1 -ss 0 -faa -af amb.af clear_octree.oct > rtrace.lux
>
>
> *DC CALCULATIONS*
>
> #Full sky DC
> oconv Materials/* scene.rad windows.rad white.sky > white_octree.oct
> gendaymtx -h -m 1 Santiago.wea > full_sky.skv
> cat Workplanes/WP.pts | rcontrib -e MF:1 -f reinhart.cal -b rbin -bn
> Nrbins -m skymat -n 4 -I -ab 8 -ad 50000 -lw 2e-5 -dc 1 -dt 0 -dj 0 -st 1
> -ss 0 white_octree.oct > DC1.mtx
> dctimestep -n 1 DC1.mtx full_sky.skv > DC1.lux
>
> #Direct sun from patches, to be sustracted
> xform -m scene.rad > black_scene.rad
> oconv Materials/* black.rad black_scene.rad windows.rad white.sky >
> black_octree.oct
> gendaymtx -h  -m 1 -d Santiago.wea > sun_only_sky.skv
> cat Workplanes/WP.pts | rcontrib -e MF:1 -f reinhart.cal -b rbin -bn
> Nrbins -m skymat -n 4 -I -ab 1 -ad 50000 -lw 2e-5 -dc 1 -dt 0 -dj 0 -st 1
> -ss 0 black_octree.oct > DC2.mtx
> dctimestep -n 1 DC2.mtx sun_only_sky.skv > DC2.lux
>
> #Sharp sun addition
> oconv Materials/* black.rad black_scene.rad windows.rad suns.rad >
> suns_octree.oct
> gendaymtx -h -m 6 -5 Santiago.wea > direct_sun_M6_sky.skv
> cat Workplanes/WP.pts | rcontrib  -n 4 -I -ab 1 -ad 50000 -lw 2e-5 -dc 1
> -dt 0 -dj 0 -st 1 -ss 0 -e MF:6 -f reinhart.cal -b rbin -bn Nrbins -m solar
> suns_octree.oct > directsun.mtx
> dctimestep -n 1 directsun.mtx direct_sun_M6_sky.skv > directSun.lux
>
>
>
> The results are horrible!!! So, any help would be awesome!!! THANKS
>
>
> --
> *Germán Molina L.*
> Ingeniero Trainee
> Hunter Douglas Chile S.A.
> Celular +569 89224445
>
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