[Radiance-general] Cumulative calculations of irradiance

[Greg Ward]

Hi Iván,

Regarding your calculation of kWh / m2, you should probably use -m  
0.0005 if you are adding up values every half hour rather than once  
per hour.

As for the -i option not doing quite what you want, glass and other  
transparent surfaces are excepted for this calculation and pass  
through to whatever lies beyond.  Under circumstances where you are  
after a rendering of visible surfaces, this is usually preferred.  To  
get the irradiance on every surface regardless of type, use:

	vwrays -x xres -y yres [view options] -fd \
		| rtrace -fd -h -opN scene.oct \
		| rtrace -fdc -I `vwrays -d -x xres -y yres [view options]`scene.oct \
		> irradiance.pic

Vwrays produces the view rays, which the first rtrace very quickly  
turns into intersection points and surface normals.  These are then  
passed to the second rtrace as irradiance measurement points.  The  
second invocation of vwrays in backwards quotes is simply there to  
tell the second rtrace the image dimensions.

I hope this helps.
-Greg

> From: Iván Pajares Sánchez <defunkt at pobox.com>
> Date: June 5, 2008 2:35:36 AM PDT
>
> Hello group,
>
> I am working out some simulations to get some figures that help me  
> estimate irradiance on a building for thermal load comparison. What  
> I am trying to do is to gauge the range of numbers one can get and  
> the differences in different part of the building so I have a basis  
> to speak to the engineer.
>
> To do this I generate my Radiance model with only one material to  
> start with with 50% reflectance. I generate a 1/2 hour series of  
> renderings (with -i switch on).
> Afterwards I add up the irradiances with pcomb to get one picture  
> from which to get the falsecolor scale in kWh / m2.
>
> I'm using falsecolor with -m = 0.001 to get the output in kWh / m2  
> to get daily cumulative irradiances. Is this approach correct?
>
> I'm doing this because RADMAP for windows fails to work (even the  
> example files that come with it) so I wanted to play around with  
> radiance and learn something on the way.
>
>
> I guess my next step is to feed real irradiance data into radiance  
> and foloow the procedure outlined before, Am I in the proper  
> direction?
>
> Thanks for any feedback!
>
> Iván Pajares