[Radiance-general] brightdata factor ?

[Giulio Antonutto]

Christian,
that number, M, in your file is:

1/A =  PI x r^2 = 3.1415927 x 0.0065^2 = 75.3396

it means that in the radiance data file all the numbers are divided by
179 and are intensities (cd/179).

at the end the whole product, datafile numbers x M should be = 
(intensities) x 1/179 x 1/A

and you can freely move these products across brightdata, light, or the
datafile... what it matters is the overall result.

hope it helps
ciao
G.

PS in some cases it is: 
intensities x Flux/1000 x 1/179 x 1/A, 
it depends on the input data, i.e. cd or cd/klm.



-----Original Message-----
From: radiance-general-bounces at radiance-online.org
[mailto:radiance-general-bounces at radiance-online.org] On Behalf Of
Christian Fusenig
Sent: 14 May 2006 20:03
To: radiance-general at radiance-online.org
Subject: [Radiance-general] brightdata factor ?

Hi @ all,

i created an IES file from measured data. This is the IES file:
---------------------------------
TILT=NONE
1 26000 1 26 1 1 2 -0.13 0 0 1 1 1000
0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25 27.5 30
  32.5 35 37.5 40 42.5 45 47.5 50 52.5 55 57.5 60 90
0
10457 10289 10178 10122 10019 9806 9687 9325 9095 8444
 7951  7068  6531  5755  5205 4939 4718 4431 4325 4319 
 4457  4591  4966  5406  5919   
0
-------------------------------------

Converted to Radiance, the file looks like this:

-------------------------------------------
# ies2rad -t default -c 1.37798146 0.913149838 0.35163837 -m 1 -o 
light/1ff_100
# Dimensions in meters
# ...
#<[WATT]     1000
# 1000 watt luminaire, lamp*ballast factor = 1

void brightdata 1ff_100_dist
4 flatcorr light/1ff_100.dat source.cal src_theta
0
1 75.3396

1ff_100_dist illum 1ff_100_light
0
0
3 1.37798 0.91315 0.351638

1ff_100_light ring 1ff_100.d
0
0
8
    0 0 -0.00025
    0 0 -1
    0 0.065

## Translated from MGF Version 2.0
## mgf2rad -g 0.183848
## mgf2rad ies/ ##############################
------------------------------------------------------------

What i don't understand is the factor of  '75.3396' in line 3 of 
brightdata. Isn't it supposed to be '1'?
Thanks and regards,

Christian







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