[Radiance-general] Direct horizontal illuminance

[Phillip Greenup]

Dear Dennis,

You will need to define the light entity 'solar' before applying it to the 'sun'. The definition you have provided for 'sun' tells Radiance the direction toward the sun and it's angular size, but it doesn't tell it how bright it is.

An example of the type of definition you require is:
void light solar
0
0
3 1000 1000 1000

This would create a sun with radiance 1000 W/m2/sr in each of the red, green and blue colour bands. Note that I have used 1000 as an example; a normal sun brightness would be more than 1e6 W/m2/sr.

If you want to achieve a known direct horizontal illuminance, you can scale these numbers to suit your target value.

I hope this helps,
Phil.

From: TSANG Kai Kwong [mailto:kaiktsang4-c at my.cityu.edu.hk]
Sent: Friday, 22 December 2017 3:25 PM
To: radiance-general at radiance-online.org
Subject: Re: [Radiance-general] Direct horizontal illuminance


Dear Dr. Greenup,

Thank you for your help.

I have tried to insert the sun in the sky.rad. However, I am not able to convert the .rad into .oct using "oconv.exe" because of "undefined modifier "solar"".

Here is my sky.rad:

solar source sun
0

0

4 -0.875487 0.087344 -0.475282 0.5

void brightfunc skyfunc

2 skybright ssldlum.cal

0

10 177 30.2 4 -0.7 0 -1 0 -0.675211 -0.729544 -0.108883



skyfunc glow ground_glow

0

0

4

     1 .8 .5 0



ground_glow source ground

0

0

4

     0 0 -1 180



skyfunc glow sky_glow

0

0

4 .991 .991 1.101 0



sky_glow source sky

0

0

4 0 0 1 180
Best regards,
Dennis Tsang
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