Understanding illum correctly?

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.



From: Mark Shewfelt <[email protected]>
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?


Mark Shewfelt
Enermodal Engineering Ltd.
Kitchener Ontario Canada