[Radiance-general] Difference between climate data and Radiance data.

[Andrew McNeil]

Hiroaki,

I agree with Greg that it's not clear what you're doing, but I'm assuming
that you're using the climate data to create a sky file and then comparing
the horizontal direct illuminance to horizontal direct calculated from
solar angle and the climate data.

Integrating over pixels of a rendering is a round about way of getting at
illuminance. There's also potential error introduced by the pixel
resolution of the sun in the image. To address this you should make your
images very large (~4000x4000 pixels). Also I think you want to multiply
the result by 4, not 16, in your rcalc command (you have to multiply by
4/pi to counter the effect of the black edge pixels and also multiply by pi
as part of your hemisphere integration - pi cancels and the 4 remains).
 This plus fixing your view as Greg suggests should give agreement.

You might consider instead using rtrace with -I+ (capital i) and -ab 1 like
so:

rtrace -h -I+ -ab 1 -aa 0 -ad 10000 -lw 1e-5 sky.oct


Also gendaylit is probably a better option than gensky for creating a sky
from a weather file. Gensky will give agreement in this test, but the sky
generated won't as valid as one generated by gendaylit.

Best,
Andy


On Fri, May 2, 2014 at 12:39 PM, Greg Ward <gregoryjward at gmail.com> wrote:

> Dear Hiroaki,
>
> Although I am not sure what you are attempting to match or how you are
> doing so, but I can at least say that your view file is probably wrong.
>
> The "-vtl" option specifies a parallel view, when you no doubt want a
> hemispherical projection ("-vth") in this case.
>
> Best,
> -Greg
>
> *From: *濱田裕章 <hiroaki.mp.3 at gmail.com>
>
> *Subject: *[Radiance-general] Difference between climate data and
> Radiance data.
>
> *Date: *April 30, 2014 12:28:19 AM PDT
>
>
>  Dear all,
>
>
>
> I’m going to study distribution of solar radiation in buildings in the
> city by using GIS data.
>
> I’d like to match a climate data with Radiance data. But, I couldn’t get
> the same value.
>
> Does anyone know the idea how to match climate data and Radiance data?
>
> My method is below.
>
> Obtain an illuminance by using Pvalue command.
>
> views file is below.
>
> rview rvu -vtl -vp 0 0 10 -vd 0 0 1 -vu 0 1 0 -vv 180 -vh 180 -vo 0.0 -va
> 0.0
>
> skies file is below.
>
> !gensky 6 22 5:0 -B 46 -R 37.12796503 -a 43.035 -o -141.199 -m -135.0
>
> skyfunc glow skyglow
>
> 0
>
> 0
>
> 4 1.000 1.000 1.000 0
>
> skyglow source sky
>
> 0
>
> 0
>
> 4 0 0 1 180
>
> skyfunc glow groundglow
>
> 0
>
> 0
>
> 4 0 0 0 0
>
> groundglow source ground
>
> 0
>
> 0
>
> 4 0 0 -1 180
>
> bash file is below.
>
> pvalue -h -H -d t1_1.pic | total -m | rcalc -e '$1=($1+$2+$3)/3*16'>t1.dat
>
> The result is below.
>
> time       ND*1      Altit*2    HD*3=R               B*4         no
> Gensky           -i            -u
>
> 4:00       0            0.278     0                          7
> 4.0464                 9.4688   8.9056
>
> 5:00       225        9.498     37.12796503       46
> 25.44                   52.128   58.368
>
> 6:00       445        19.824   150.9137426       76
> 43.12                   75.744   96.752
>
> 7:00       588        30.608   299.3870167       82
> 51.872                 79.744   104.256
>
> 8:00       636        41.547   421.8169494       108
> 82.752                 112.752 137.504
>
> 9:00       618        52.252   488.6593632       151
> 149.504               190.56   192.48
>
> 10:00     557        61.986   491.7378991       220
> 295.04                 371.04   279.04
>
> 11:00     519        68.96     484.3982757       264
> 451.04                 590.08   335.04
>
> 12:00     459        69.842   430.8843623       300
> 534.08                 694.08   380.96
>
> 13:00     395        63.995   355.0085362       348
> 495.04                 625.92   443.04
>
> 14:00     532        54.691   434.1369031       207
> 220.48                 276.96   263.04
>
> 15:00     397        44.127   276.411698         219
> 176.48                 236.48   279.04
>
> 16:00     442        33.203   242.0423097       160
> 104.752               156.496 203.52
>
> 17:00     164        22.352   62.36849428       132
> 75.744                 129.504 167.52
>
> 18:00     35          11.887   7.209375721       62
> 34.128                 67.744   78.752
>
> 9:00       0            2.249     0                          7
> 3.976                   9.032     8.9056
>
> *1: Normal direct solar radiation
>
> *2: Horizontal direct solar radiation
>
> *3: Solar altitude
>
> *4: Horizontal total solar radiation
>
>
>
> Best regards,
>
>
>
> Hiroaki
>
>
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