[Radiance-general] FW: Gensky Question

[Giulio Antonutto]

Nick,

-R -B are supposed to specify direct and diffuse contribute.
a quick and easy check is to create a -s (diffuse only) and a +s
(global) sky with the same -R -B and check illuminances at a point (0 0
0, 0 0 1)
Now try without the sky dome and +s (direct only) and see...
you should get diffuse and global and direct values.
Please try it.


About the source primitive, you need it all the time.
Coefficients can be just (1 1 1) for the sky 
and a reduction like (0.1 0.1 0.1) or (0.2 0.2 0.2) for the ground
depending to the model you are working on.
If you use your coefficients you will be working with colour but you
need to check that the photopic average is correct.


Hope this is +s,
i.e. 'clear' 
:-)

Ciao
G>







-----Original Message-----
From: radiance-general-bounces at radiance-online.org
[mailto:radiance-general-bounces at radiance-online.org] On Behalf Of Nick
Devlin
Sent: 22 November 2006 09:56
To: radiance-general at radiance-online.org
Subject: [Radiance-general] FW: Gensky Question


Hi All, 

I have a GENSKY question that I cant find the answer to in the archives.
I
suspect that the answer is straightforward, but I am now challenging all
my
old assumptions as I have just switched from old school desktop radiance
to
3R7P2 with photon mapping running under Ubuntu on VMware Workstation.
Daunting, but I like it!

Perhaps first I should state that I am aware from the listings that
perhaps
I should be using Gendaylit rather than Gensky, but I have not managed
to
compile it yet. Compiling makes me anxious. I used Francesco's Linux
binaries in the end as I couldn't get photon map to compile properly
after
3R7P2. My /bin and /lib files are not in the standard location, but I
have
altered PATH & RAYPATH accordingly. 

So, to the questions:

Firstly, I have some data for sky brightness from BRE Availability of
Daylight, for diffuse and direct illuminance. If for example, I have
illuminance values of 34 klux diffuse and 26 klux direct can I
explicitly
set these in Gensky (assuming 179lux per watt) with 

Gensky (location details, azimuth etc) +s -B 189 -R 145.25 > skyfile.rad

My concern is whether -B or -R overrides the other, or will I ultimately
result in approximately total 60klux horizontal illuminance? 

Secondly, do I have to manually add the following to the bottom of
skyfile.rad. I presume that I don't need to alter any of the parameters
here
for a basic sky and ground plane and that it references the skyfunc
output
from the gensky command. 

skyfunc glow skyglow
0
0
4
	.85 1.04 1.2  0

skyglow source sky
0
0
4
	0 0 1  180

skyfunc glow groundglow
0
0
4
	.8 1.1 .8  0

groundglow source ground
0
0
4
	0 0 -1  180

Finally, if I explicitly set -B & -R for an intermediate sky with +i
does
the +i setting result in an adjustment to the -B & -R values? 

Many thanks in advance

Nick Devlin. 
 


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