[Radiance-general] Determining Direct component and Internally Reflected Component.

[John Mardaljevic]

Arvinder,

For a sky without sun (whatever the sky type), setting -ab 1 for
an illuminance(*) calculation will give the direct sky component
of daylight illuminance.  For the inter-reflected component, set
higher -ab values and subtract the values you got for -ab 1.
And, of course, the ambient value should be zero.

For the direct sky calculation, all opaque materials should be
set to diffuse only.  Otherwise you may get some specular reflections
happening at -ab 1.

-John Mardaljevic

(*) Of course, we first compute irradiance and convert to illuminance.

-----------------------------------------------
Dr. John Mardaljevic                     
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972   
+44 (0) 116 257 7981 (fax)

jm@dmu.ac.uk   
http://www.iesd.dmu.ac.uk/~jm