gensky result different from that in Axel's tutorial

radiance-general
1

Hi, Radiance experts:

Following Axel Jacobs' "Basic Radiance Tutorial" on page 23,
I run "gensky 12 09 14 -a 51 -o 0 -m 0" in the Terminal of Mac OS X, the
output is (quoted in # symbol):

···

#####################################################
# gensky 12 09 14 -a 51 -o 0 -m 0
# Local solar time: 14.14
# Solar altitude and azimuth: 11.0 29.9
# Ground ambient level: 7.8

void light solar
0
0
3 2.72e+06 2.72e+06 2.72e+06

solar source sun
0
0
4 -0.489041 -0.851114 0.190903 0.5

void brightfunc skyfunc
2 skybr skybright.cal
0
7 1 3.37e+00 3.54e+00 2.98e-01 -0.489041 -0.851114 0.190903
#####################################################

However, two parts of this result are different from that wrote in Axel
Jacobs' tutorial:

1) In Axel's tutorial, line 4 of the output is:
# Ground ambient level: 8.7

2) In Axel's tutorial, the last line of the output is:
7 1 3.76e+00 3.72e+00 2.98e-01 -0.489041 -0.851114 0.190903

So, Which output is the correct one? What might causes the differences?

Thanks!

Ji

BTW, I'm using the latest Radiance (4R0) compiled for Mac OS downloaded from
http://radsite.lbl.gov/radiance/framed.html

2

The default turbidity factor changed in 2006, but it seems Axel must have been using an older version of gensky. Neither the new result or the old result is "correct" in the sense that the sky is unreal. Absolute values never mean much in daylighting calculations unless you have a measured sky. This is why we recommend using the -B (-r) and -R (-r) options to calibrate gensky output against measurements if you care about absolute levels.

-Greg

···

From: Ji Zhang <[email protected]>
Date: June 23, 2010 7:17:03 AM PDT

Hi, Radiance experts:

Following Axel Jacobs' "Basic Radiance Tutorial" on page 23,
I run "gensky 12 09 14 -a 51 -o 0 -m 0" in the Terminal of Mac OS X, the output is (quoted in # symbol):

#####################################################
# gensky 12 09 14 -a 51 -o 0 -m 0
# Local solar time: 14.14
# Solar altitude and azimuth: 11.0 29.9
# Ground ambient level: 7.8

void light solar
0
3 2.72e+06 2.72e+06 2.72e+06

solar source sun
0
4 -0.489041 -0.851114 0.190903 0.5

void brightfunc skyfunc
2 skybr skybright.cal
0
7 1 3.37e+00 3.54e+00 2.98e-01 -0.489041 -0.851114 0.190903
#####################################################

However, two parts of this result are different from that wrote in Axel Jacobs' tutorial:

1) In Axel's tutorial, line 4 of the output is:
# Ground ambient level: 8.7

2) In Axel's tutorial, the last line of the output is:
7 1 3.76e+00 3.72e+00 2.98e-01 -0.489041 -0.851114 0.190903

So, Which output is the correct one? What might causes the differences?

Thanks!

Ji

BTW, I'm using the latest Radiance (4R0) compiled for Mac OS downloaded from RADIANCE WWW server