Hi Victor,<br><br>For daylight factor calculation in Radiance you can use <b>dayfact</b> script included in Radiance distribution.<br>It has interactive input ,so you can input all data you need, and it will calculate Df and various related images.<br>
<br>If you want to calculate in only in few points, you can do it simple, calculate illuminance in points inside the building for overcast sky (with rtrace program), and just divide this values with overcast sky horizontal illuminance value.<br>
For example overcast sky for Paris for diffuse horizontal illuminance 10000lux<br>gensky 6 22 +11 -c -a 48.817 -o -2.483 -m -15 -B 55.866<br><br>-B is irradiance an is calculated as 10000/179=55.866<br><br>And rtrace command would be like:<br>
rtrace -I+ -h- -oov -ab 5 -ad 1024 -as 256 -aa 0.15 -ar 1000 octree.oct| rcalc -e '$1=$1; $2=$2; $3=$3; $4=(0.265*$4+0.670*$5+0.065*$6)*179'<points.txt >output.txt<br><br><br>
Note that you should put appropriate calculation parameters in rtrace to have accurate results.<br>rcalc command above converts rtrace output from RGB to 1 illuminance value.<br><br>So when you got illuminances inside the building just divide them with 10000, to get DF values, or directly in rcalc divide with 10000 to get Df values on output:<br>
$4=(0.265*$4+0.670*$5+0.065*$6)*179/10000<br><br>Hope this helps,<br>Marija<br><br><div class="gmail_quote">On Thu, Dec 10, 2009 at 10:04 AM, Victor Li <span dir="ltr"><<a href="mailto:victorpermanent@gmail.com">victorpermanent@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Dear:<br><br>Daylight factors are expressed as the percentage of natural light falling on a work surface compared to that which would have fallen on a completely unobstructed horizontal surface under exactly the same sky conditions. Thus, a daylight factor of 5% on an internal surface means that it received only 1/20th of the maximum available natural light.<br>
<br>so we can calculate daylight factor by RADIANCE with a overcast sky. Then i calculated the illuminance under overcast sky. I found the distribution of illuminance and skyfactor in the room is different. For example, in the room ratio of minimum to average of daylight and illuminance are quite different. Would you tell me the reason?<br>
<br>Best Regards!<br>
<br></blockquote></div><br>