[Radiance-general] Any method to calculate sky view factor in Radiance?

[Katsuya Obara]

Dear Raphael,

Thank you very much for your answer.
Since I am not familiar with Unix, may I ask you how I should write in Microsoft batch file for following part?
cat points | rtrace -h -ab 1 -I uni.oct | rcalc -e 'SVF=$1;$1=SVF;'
Especially, I could not figure out what points mean.

Thank you.
Katsuya

-----Original Message-----
From: Compagnon Raphaël [mailto:Raphael.Compagnon at hefr.ch] 
Sent: Thursday, April 12, 2018 2:38 PM
To: Radiance general discussion
Subject: Re: [Radiance-general] Any method to calculate sky view factor in Radiance?

Hello

A simple approach is to compute the illuminance level under a uniform sky.
First define a uniform sky (uni.rad) like this:

void glow sky_glow
0
0
4 0.318309886 0.318309886 0.318309886 0
sky_glow source sky
0
0
4 0 0 1 180

Note that the radiance value 0.318309886=1/PI This makes the illuminance value computed for an unobstructed horizontal plane equal to 1 and this matches in fact the SVF value!


To compute SVF values for several points, then use rtrace with option -I like this:


oconv uni.rad >uni.oct
cat points | rtrace -h -ab 1 -I uni.oct | rcalc -e 'SVF=$1;$1=SVF;'

where points is a file where calculation points are stored as:
x y z xdir ydir zdir

For instance using these three points you can check that SVF values are well computed as 1 for an horizontal plane and 0.5 for vertical planes:
0 0 0 0 0 1
0 0 0 0 1 0
0 0 0 1 0 0

Of course SVF values are usually more interesting to compute for scenes containing objects... These should be defined in a scene file and then merged in the octree before doint the SVF calculations:


oconv uni.rad myscene.rad >scene.oct
cat points | rtrace -h -ab 1 -I scene.oct | rcalc -e 'SVF=$1;$1=SVF;'


Hope this will help you!
Raphaël







________________________________
De : Katsuya Obara <katsuya.obara at arup.com> Envoyé : jeudi 12 avril 2018 01:54:46 À : radiance-general at radiance-online.org
Objet : [Radiance-general] Any method to calculate sky view factor in Radiance?

Dear all,

I want to calculate sky view factor.
Trying to find in google, I could not find solid information which I can refer to.
Could anyone tell me what kind of approach I can have to calculate sky view factor?

Thank you.
Katsuya


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