[Radiance-general] Re: Glare and evaluation of lightshelves

[Greg Ward]

Hi Carlos,

Glare calculations are quite tricky, because they are sensitive to the 
exact view you choose to calculate them, and there are a number of 
choices for glare indices as well, none of them terribly well-suited to 
daylight.  (Not in glarendx, at least.)

It is impossible to determine anything from your description of your 
situation.  Are you giving fisheye views to findglare?  What do these 
images look like?  Are you giving findglare an octree so that it may 
call rtrace?

And for the group, has anyone determined that findglare works correctly 
in Desktop Radiance?

-Greg

> From: Carlos Ochoa <carlosochoam@yahoo.com>
> Date: Sun Nov 16, 2003  5:09:15  AM US/Pacific
>
> Hi there!
>
> I'm using DR 2.0 and I've been making parametric
> calculations comparing daylight systems -a room with high
> reflectances, and the same room but adding in one case a
> lightshelf and in another an anidolic reflector. The room
> faces south, and I am evaluating them through daylight
> glare index (dgi).
>
> To give more details, the room measures 8x12 meters, with a
> ceiling height of 2.70 meters. The window is 8x1.70m
> (placed on the 8m side).
>
> The materials: ceiling: brushed aluminium (r=80%), walls:
> beige (r=65%) and floor: blue (r=20%). These reflectances
> were taken from recommendations from literature.
>
> The light shelf has a length of 1m and is also made from
> brushed aluminium and is placed 2.1 meters from the floor.
> (half is inside the room and half outside).
>
> I generated pictures with winrview, both looking into the
> window and looking sideways, and then used the two main
> glare routines available (findglare and glarendx).
>
> According to other studies (including those of people who
> have used Radiance) the lightshelf should have a lower
> glare index than the room without any addition, but to my
> surprise and in the two picture cases, it is the opposite!
> (absolute illuminance levels are OK, though)
>
> In the beggining I thought that my ceiling was too specular
> (50%) but then I changed it to another with similar
> reflectance but no specularity... and the results are still
> the same!
>
> What could be wrong?
>
> Carlos