[Radiance-general] sky visibility

[Iebele]

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
> 
> 
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