[Radiance-general] Irradiation on standing subject with Radiance

[Gregory J. Ward]

P.S.  I just realized that to be a fair average, the number of samples on the cap should be proportional to the area, and same for the body.  A cap of radius 0.2 is 1/20th as large as the cylinder body of height 2, so in my example, there should be 20 times more samples on the body.  That means 5 samples on the cap would be paired with 100 samples on the body, or 105 samples in total.

-Greg

> From: Greg Ward <gward at lmi.net>
> Subject: Re: [Radiance-general] Irradiation on standing subject with Radiance
> Date: September 21, 2015 11:50:28 AM PDT
> 
> Hi Ruggiero,
> 
> I don't think the number of points is going to affect your rcontrib calculation that much.  You can always trade off the number of ambient divisions (-ad) to get more samples on the prism (or cylinder) for the same cost.  Here's an example set of commands.
> 
> # Generate 5 random sample positions on cap at height 2 with radius 0.2:
> 
> cnt 5 | rcalc -e 'HT:2;RAD:0.2' \
> 	-e 'rrad=RAD*sqrt(rand(.836*recno+.238));phi=2*PI*rand(-.3582*recno+.861);' \
> 	-e '$1=rrad*cos(phi);$2=rrad*sin(phi);$3=HT;$4=0;$5=0;$6=1' > samps.txt
> 
> # Generate 50 random body sample positions and directions:
> 
> cnt 50 | rcalc -e 'HT:2;RAD:0.2' \
> 	-e 'rht=HT*rand(.571*recno-.7633);phi=2*PI*rand(-.6716*recno-.1023)' \
> 	-e '$1=RAD*cos(phi);$2=RAD*sin(phi);$3=rht;$4=cos(phi);$5=sin(phi);$6=0' >> samps.txt
> 
> # average together 55 sample positions using rcontrib:
> 
> rcontrib -c 55 [other options] scene.oct < samps.txt > daycoef.mtx
> 
> Does this make sense?
> 
> -Greg
> 
>> From: Ruggiero Guida <ruggiero.guida at gmail.com>
>> Date: September 21, 2015 1:45:20 AM PDT
>> 
>> That makes sense. So I guess that the third approach is the only way forward. 
>> 
>> I was thinking to define the subject as a prism with a rectangular base and maybe define a point or two for each face, so 5 points in total. 
>> 
>> Do you think this would be enough?
>> 
>> _____________________________
>> From: Greg Ward <gregoryjward at gmail.com>
>> Sent: Monday, September 21, 2015 10:52 a.m.
>> 
>> Well, the projected area of a cylinder is roughly the diameter times the height times the sine of the angle between the cylinder's axis and the sky patch (or solar disk) direction.  This would work if you didn't have the complex urban surroundings.  With the surroundings, there's no way I know to avoid a more complete view factor calculation, which is what rcontrib gives you.
>> 
>> -Greg
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.radiance-online.org/pipermail/radiance-general/attachments/20150921/becc506c/attachment.html>