[Radiance-general] sky visibility

[Ji Zhang]

Thank you very much, Giulio! will digest ur suggestions and give it a try
on the combined use of vwray + rtrace + rcalc.
- Cheers, Ji.

On Sun, Oct 21, 2012 at 6:09 AM, giulio antonutto <antonutto at yahoo.it>wrote:

> ok,
> setup a view out of the window, with -a.
> save the view file.
> use vwrays to generate the vectors and starting point to sample the sky
> shoot with rtrace
> use -av 1 1 1 so that you do not need to have a sky but all glows.
> then pipe the rtrace to rcalc and use if($1,1,0)  then total.
> the overall number of hits that are recorded is the number of intersection
> to the model
> you need then to check the overall resolution of your image and account
> for the fact that you should be considering the inner 180 deg. circle.
> Sorry have no time to write up this for you,
> but to be fair there is already (and below too) a lot that you could try.
> If you have no time to experiment or are simply looking for the easy
> copy/paste solution amen.
> I meant differently.
> in any case, all the best
> G
>
>
>
> On 20 Oct 2012, at 13:46, Ji Zhang <hope.zh at gmail.com> wrote:
>
> 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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