[Radiance-general] sky visibility

[Andrew McNeil]

You could use vwrays with rtrace instead of rpict.
Andy


On Fri, Nov 30, 2012 at 8:51 AM, Iebele <iabel at iebele.nl> wrote:

> Hi Ji,
>
> Concerning the rpict part of your problem, you might consider an approach
> that divides the solution into series of scanlines equal to the number of
> nodes/processors you have available in your parallel system. Use piece
> instead of rpict, in such case.
>
> - iebele
>
>
>
> Op 30 nov. 2012, om 12:50 heeft Ji Zhang het volgende geschreven:
>
> Dear list,
>
> I'd like to ask if the Radiance way to calculate sky exposure as explained
> below can be further optimized.
>
> This method is quite accurate, but it is just not fast enough for us (0.2
> second per sensor).
>
> It seems the Radiance programs used in this approach, such as rpict,
> pcomb, pvalue, etc. are not applicable to harvest the power of parallel
> processing, such as what the "-n" option does for rtrace.
>
> Maybe I'm just too greedy, but is there a way to further enhance the
> efficiency of the individual Radiance command in this method?
>
> Thanks in advance!
>
> - Ji
>
>
> On Fri, Oct 26, 2012 at 2:11 AM, Ji Zhang <hope.zh at gmail.com> wrote:
>
>> Hi, Lars, Thanks for your detailed explanation!
>>
>> The following bash script is put up according to the suggestions from all
>> previous replies to this post. This method is view type independent.
>> Anyway, I'd appreciate further advices from the list to make it more
>> succinct and efficient, or point out the loopholes if there are any.
>>
>> # start__________________________
>> # calculate Sky Exposure Factor
>> # which is defined as the ratio between
>> # the solid angle subtended by visible sky patch/patches
>> # and that of the unobstructed sky hemisphere (which is 2*PI)
>> oconv ./plastic_mat.rad ./geom.rad > ./SkyEF_scene.oct
>> rpict -av 1 1 1 -vf ./view_vts.vf -x 1000 -y 1000 ./SkyEF_scene.oct |
>> pcomb -e 'solidAngle=S(1);ro=if(ri(1),0,solidAngle);
>> go=if(gi(1),0,solidAngle); bo=if(bi(1),0,solidAngle)' -o - | pvalue -h -H |
>> rcalc -e '$1=$3' | total | rcalc -e '$1=$1/2/PI' > ./SkyEF_results.txt
>> # end__________________________
>>
>> The contents of "view_vts.vf" (note that the location of the view point
>> is slightly away from the surface of the scene geometry):
>> rvu -vts -vp 0 0 0.001 -vd 0 0 1 -vu 0 1 0 -vh 180 -vv 180 -vo 0 -va 0
>> -vs 0 -vl 0
>>
>>
>> The following step-by-step break down of the commands might be useful for
>> debugging purpose.
>>
>> # start__________________________
>> oconv ./plastic_mat.rad ./geom.rad > ./SkyEF_scene.oct
>>
>> rpict -av 1 1 1 -vf ./view_vts.vf -x 800 -y 800 ./SkyEF_scene.oct >
>> ./SkyEF_vts.hdr
>>
>> cat ./SkyEF_vts.hdr | pcomb -e 'omega=S(1);ro=if(ri(1),0,omega);
>> go=if(gi(1),0,omega); bo=if(bi(1),0,omega)' -o - > ./SkyEF_solidAngle.hdr
>>
>> cat ./SkyEF_solidAngle.hdr | pvalue -h -H >
>> ./SkyEF_xpos_ypos_solidAngleVal.txt
>>
>> cat ./SkyEF_xpos_ypos_solidAngleVal.txt | rcalc -e '$1=$3' | total >
>> ./SkyEF_total_solidAngle_of_visible_sky.txt
>>
>> cat ./SkyEF_total_solidAngle_of_visible_sky.txt | rcalc -e '$1=$1/2/PI' >
>> ./SkyEF_results.txt
>> # end__________________________
>>
>>
>> Thanks again for the help from all of you!
>> - Ji
>>
>>
>>
>> On Thu, Oct 25, 2012 at 4:20 PM, Lars O. Grobe <grobe at gmx.net> wrote:
>>
>>> Hi Ji!
>>>
>>> The functions S(n) and T(n) are available in pcomb. To make an image
>>> "solid_angles.hdr" with pixel values (r=g=b) being equal to the solid angle
>>> of the pixel in sr, you would do the following:
>>>
>>> cat image.hdr |  pcomb -e 'omega=S(1); ro=omega; go=omega; bo=omega' -o
>>> - > solid_angles.hdr
>>>
>>> So S(n) gives, for each pixel of the n'th input image, its solid angle.
>>> To take a look, use falsecolor -m 1 -s .000008 -ip solidangle.hdr | ximage
>>> - good way to think about projections...
>>>
>>> Cheers, Lars.
>>>
>>>
>>> > Hi, Lars, thanks a lot for your advices!
>>> >
>>> > May I ask the references on the S and T function as you suggested to
>>> look up? (I didn't find any relevant infor via Radiance forum search...)
>>> >
>>> > May I also ask what the "n" in the "S(n)" denotes?
>>> >
>>> > Thanks again!
>>> >
>>> > - Cheers, Ji
>>>
>>>
>>> _______________________________________________
>>> Radiance-general mailing list
>>> Radiance-general at radiance-online.org
>>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>>>
>>
>>
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