[Radiance-general] Re: Radiance simulations maintain 200 lux minimum?

[Greg Ward]

Hi Caroline,

There are as many possible reasons to your problem as there are option 
settings in rpict.  (I.e., a lot.)  You have to give us a little more 
detail about what settings you are using in your rad input file (if 
you're using rad) or your rendering/simulation command (if you're 
calling rpict or rtrace directly).  Posting an image if you have a 
website is also an incredible help.  If you haven't generated any 
images, I recommend you do so, even if you don't require them for your 
analysis.  Renderings are one of the best debugging tools ever 
conceived.

-Greg

> From: Caroline Prochazka <cjprocha at yahoo.com>
> Date: April 16, 2004 11:57:45 AM PDT
>
> Hello,
> I have been running several simulations in Radiance
> for Winter and Summer solstice at Toronto latitudes.
> For noon hour simulations the results are quite
> believable along perimeter areas. I have noticed
> however, that no matter what changes I make to my
> model, the lowest illuminance reading I can generate
> anywhere inside a daylit room is between 150 and 200
> lux. For afternoon models where the sun is at a
> low-angle, the core areas of my models should be below
> 50 lux (from in-situ light measurements). I understand
> Radiance has trouble with low-angle sun simulations.
> But when I look at my noon hour models (sun very
> high), I notice that my core readings are also all
> around 200 lux...seemingly unable to drop below 200
> lux. My false colour plots do show minimum extrema
> lower than 200 lux, and areas in direct shadow, are
> shown more blue (closer to 50 lux on my scale). From
> in-situ measurements at desk height, though, it would
> seem that the drop off of illuminance levels from the
> perimeter to the core of a room is not adequately
> represented in my Radiance models. Can anyone offer a
> suggestion why my illuminance values, for the most
> part, bottom out at 200 lux?
>
> Regards,
> Caroline