[Radiance-general] Irradiation on standing subject with Radiance

[Ruggiero Guida]

Thanks Greg. Really appreciate it. Let me digest it, test it and I will
report back.

Cheers

On 22 September 2015 at 03:02, Gregory J. Ward <gregoryjward at gmail.com>
wrote:

> Oh, and be sure to use the rcontrib -I+ option.  Corrected version
> immediately below.
>
> # 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 100 random body sample positions and directions:
>
> cnt 100 | 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 105 -I+ [other options] scene.oct < samps.txt > daycoef.mtx
>
> ============
>
> *From: *"Gregory J. Ward" <gregoryjward at gmail.com>
>
> *Date: *September 21, 2015 11:54:14 AM PDT
>
>
> 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
>
>
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>
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