Hi Victor,<br><br>You don't need 2 calculations, just one. <br>With the overcast sky:<br>gensky 12 21 12.00 -c -a 31.400 -o -121.400 -m -120.000 -B 0.558659,<br>calculate internal illuminances with rtrace, and then just divide this values with 100lux (sky diffuse horizontal illuminance).<br>
No need to calculate illuminances in the same point when there is no building, since diffuse horizontal illuminance means exactly that:<br><p><b><a name="evd"></a></b></p> <a href="http://www.satel-light.com/guide/glosatod.htm#evd"><b>diffuse horizontal illuminance</b></a> :Illuminance produced by the visible part of the diffuse solar radiation on a horizontal surface on the earth.<br>
<br>Also, I think you should use sky with higher diffuse illuminance, at least 1000lux, because with such low outside lux, like the ones you have, results inside may be too low, and errors due to ambient calculation may be more visible.<br>
<br>Hope this helps,<br>Marija<br><br><div class="gmail_quote">On Wed, Dec 16, 2009 at 10:57 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;">Actually i just export the model from ECOTECT to RADIANCE, and i chang some parameters and run the simulation manually like Marija has shown above.<br>
<br>The first time i calculated the daylgith factor in a grid<br>I run it by define: gensky 12 21 12.00 -c -a 31.400 -o -121.400 -m -120.000 -B 0.558659,<br>
-B 0.558659 means the diffuse horizontal illuminance is 100lux outside then the internal illuminance is the dylight factor. <br><br>The second time i just calculated the internal illuminance in a grid under overcast sky in the same time as the first time. I defined the sky : gensky 12 21 12.00 -c -a 31.400 -o -121.400 -m -120.000 <br>
<br>In the grid, i can calculate the external diffuse horizontal illuminance at that time under overcast sky in the same point by the external diffuse horizontal illuminance = the internal illuminance/ daylight factor.<br>
However, i calculated the the external diffuse horizontal illuminance by different points the results are different. Actually the results should be the same because it the external diffuse horizontal illuminance. So why is it different?<br>
<br><br><br><br></blockquote></div><br>