Hello Willy,

I can't see why your approach shouldn't work apart from:- your not
specifying what software you are using, and the interreflections
being a problem when using many verily highly specular surfaces.

So far as materials go, for mirror in Radiance I would use MIRROR
material! Hasn't the software you use got this material? For specular-
reflector-lightpipe/in-lightwell I would use the mkillum program as
the skylight source at the top as well. Doesn't the software have
that function?

Were you aware of the guidance on Radiance material types for
Rayfront (at http://www.schorsch.com/rayfront/manual/matdef.html ),
which uses Radiance materials formats and engines? Tis most helpful,
I think. As it says, a value >0.1 for specularity is 'unusual'. Hmmm.

Good luck.

Regards,
George
<<>><<>><<>>
--- In DesktopRadiance@yahoogroups.com, "willyfaber" <willy.pane@...>
wrote:
>
> Hi all,
>
> to start with, I am using the Radiance tool as implemented in a
> different software suite, but I imagine that this is fairly
> irrelevant.
>
> I am looking at daylight factors in classrooms using CIE uniform
sky,
> and at the use of light wells to "brighten up" the back of deep
> classrooms. I want the maximum amount of light possible been
> channeled down the light well, so I thought that some aluminium
foil
> coating could be used. For this coating I used the following values:
> R-Refl = 0.91, B-Refl = 0.92, G-Refl = 0.92 (this is roughly the
> reflectance of polished aluminium at the different wavelength for
> Red, Green, Blue). For specularity.... I took the average of the 3
> values, so I used 0.917 (this is a pure guess, but I thought that
a
> value of between 0.9 and 1.0 would have been appropriate - ok maybe
> 1.0 would have been too optimistic, so any 0.9, 0.925, 0.95 would
> have been good). I assumed the surface to be polished, hence
> roughness = 0.
>
> Is this approach valid.. or did I completely miss the point?
> Where can I find some guidance? For example, how would I go to
> simulate a mirror?
>
> many thanks,
>
> willy
>