[Radiance-general] Fwd: radiance

[Thomas Bleicher]

On 28 Nov 2008, at 19:23, G V DEEPAK wrote:

> Hello Everyone,
>
> Thanx again Dr Bleicher, Assuming that the blinds are used to block
> the sunlight coming inside, then why is it that the blinds in my model
> are not blocking the sunlight coming in ?

It's just Mr me.

Your blinds are fine but the bright material reflects a lot of the
sun light (direct, very bright) to the ceiling. I've rendered an
image of the scene here:

http://sites.google.com/site/tbleicher/radiance

The additional illumination is - I think - caused by the light
reflected from the blinds to your sensor point. Without blinds
there is just the part of the sky you can see from the sample
point (no sun for the sky condition shown). With blinds the
sunlight is reflected diffusely at the blinds and a lot of sun light
is redirected to the sensor point that has not been there before.
Because the blinds are bright white this exceeds the light of
the sky dome so you get higher illumination values.

I haven't had time yet to do a renderings without blinds to
confirm this.

This might also explain why you get negative values for your
glare index. I'm no expert but AFAIK the glare index is calculated
from local hot spots. With your blinds there are no hot spots because
the whole window is uniformly bright. You can look into this year's
workshop presentations on glare from daylight by Jan Wienold:

http://www.radiance-online.org/radiance-workshop7/

You have to contact him directly about a copy of 'evalglare'. The
link in the presentation still does not work ...


Regards,
Thomas