[Radiance-general] Understanding illum correctly?

[Gregory J. Ward]

Hi Mark,

Yes to your first question -- this is a correct summary.

Yes also to your second question.  You didn't really need an illum  
going into mkillum, though you could have used one.  It would only  
speed up the mkillum calculation slightly, while actually making the  
subsequent rendering take longer, since rays would always be sent to  
an illum source which is forever obscured.

If you had a side-light window not computed with mkillum, then an  
illum would be appropriate there.  However, you would have to follow  
more closely the template offered in the Scene 0 Tutorial.  (See  
"Rendering with Radiance" p. 32.)  The scene description you sent was  
missing the appropriate "illum" statement for the top window.

-Greg

> From: Mark Shewfelt <MShewfelt at enermodal.com>
> Date: December 8, 2006 8:24:09 AM PST
>
> Greg, Carsten - thanks for your help. I really appreciate it. I just
> wanted to make sure I was understanding things correctly, so forgive
> these two questions:
>
> As I understand it now, there are three ways to wind up with illum
> sources in your .oct file:
> 1. Use the illum material type. Run 'oconv' as normal.
> 2. Use rad and place all of the 'illums' (using whatever secondary
> material) into a separate file. This runs mkillum automatically.
> 3. Use mkillum manually. (This is the same as 2 above?)
> As I type this out it makes perfect sense. Perhaps I have a  
> tendency to
> overthink things.
>
> One thing I noticed is that the window_dist type is replaced with a
> simple glass type. Is this because the reflectance/appearance of the
> skylight doesn't matter due to it being mostly hidden? Is it  
> correct to
> assume that if I had a sidelight window in my final scene, I would
> include the "skyfunc brightfunc window_dist 2 winxmit winxmit.cal 0 0"
> bit to make the window appear as a real window?
>
> Cheers,
>
> Mark Shewfelt
> Enermodal Engineering Ltd.
> Kitchener Ontario Canada