[Radiance-general] sky visibility

[Ji Zhang]

Dear Giulio, appreciate if you can kindly elaborate more on your
suggestions !

- Ji


On Sat, Oct 20, 2012 at 6:09 PM, giulio antonutto <antonutto at yahoo.it>wrote:

> what about vwrays and an angular view?
> then -av 1 1 1, no sky and total - positive = sky
> g
>
> On 20 Oct 2012, at 10:56, Ji Zhang <hope.zh at gmail.com> wrote:
>
> Hi, Lars,
>
> I agree with your suggestion: calculating the number of rays shooting out
> from a sensor that can reach the sky directly, and divide the value
> obtained by the total number of rays shot. This will give us the percentage
> of visible sky or sky exposure for a given sensor.
>
> However, if I understand correctly, the output of rtrace is a file, within
> which each row indicating the xyz coordinates and rgb irradiance of a given
> sensor.
>
> Is the output of rtrace which is supposed to be piped to rcalc as shown in
> your script has only one column of data and each row is the irradiance
> value of one of the sensors?
>
> So, the script might be something like:
>
> cat sensors.txt | rtrace -I  -aa XXX  -ab XXX -ad XXX -h -w scene.oct |
> rcalc -e '$1=if($1-.00001,1,0); $2=1' | total | rcalc -e '$1=$1/$2' >
> results.txt
>
> If that's the case, you're calculating the percentage of sensors that can
> see the sky (regardless of the size of sky visible to each sensor), am I
> correct?
>
> ... or I miss something critical here ...
>
> - Ji
>
>
>
> On Sat, Oct 20, 2012 at 4:05 PM, Lars O. Grobe <grobe at gmx.net> wrote:
>
>> Hi Patrick,
>>
>> Did you consider genklemsamp?
>>
>> If you just want to not apply the cosine but get either 1 or 0 for rays
>> hitting the sky or not, pipe the output from rtrace to rcalc. E.g. sum the
>> rays that are above the treshold (0.00001 here) and total number of rays
>> traced, and then get the fraction of rays over the treshold using rtrace
>> again:
>>
>> <your rtrace command> | rcalc -e ´$1=if($1-.00001,1,0); $2=1´ | total |
>> rcalc -e ´$1=$1/$2´
>>
>> That could be done using binary floats instead of ascii to make it a bit
>> more efficient using proper -if3, -of options for all commands. The same
>> can be done on e.g. fisheye images using pcomb.
>>
>> A general hint, you can also get the surface identifier (-os) at the
>> first ray intersection instead of e.g. the radiance value from rtrace and
>> pass that through grep.
>>
>> Cheers, Lars.
>>
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