[Radiance-general] Trans material and photon map

[Erico Rosa]

Hi Jan,
 
When I say "same measurements" for every point, I meant that I have the
same number (around 140 lux) for every point.
Since rtrace is running fast, I actually make new octrees, and photon
distribution files for every round (new file names) so I don't mix
things up and keep track of the changes. Rtrace - without the diffuser
and the same parameters from the first message - returned (by degree): 
 
00 > 11.1955674
10 > 8.8419795
20 > 8.90784897
30 > 6.83318662
40 > 7.42337007
50 > 6.62742577
60 > 9.50036401
70 > 14.0475395
80 > 1939.93779 (hot spot)
90 > 23.4809313
100 > 1893.626 (hot spot)
110 > 18.7999635
120 > ...
 
That's about what I expected. Then I ran another (new) rtrace with the
diffuser/trans material below (I tried to keep it simple) and rtrace
returned the 140 lux for every point mentioned above:
 
void trans mat_dif
0
0
7 1 1 1 0 0.8 0
 
So, my guess is that trans is scattering light evenly inside the sphere,
which is odd since the diffuser is pointing down.
 
Erico
 
> Hi Erico,
 
> did you erase the p-map files(pipe80.gpm,pipe80.cpm) between the two 
> variants(with and without the diffusor)?
 
> If not, you used the same photon distribution for both cases and 
> therefore end up with the same illuminance values.
 
> If you erased the files, what are the parameters for trans you used?
 
> Jan
 
>> Erico Rosa wrote:
 
>> Hi folks,
>>
>> I have built a scene where a 5.6m tall cylinder is piping sunlight 
>> (solar altitude: 80) inside a 5-meter radius sphere (bubble). The 
>> tube's origin is in the center of the sphere and it ends at the top
of 
>> the sphere. I have set the rtrace measurement points inside the
sphere 
>> at every 10 degrees (180 total), so I can transform that in an IES 
>> file later on. The rtrace (and rpict) of the photon-mapping is
running 
>> fine showing the specular reflection on the bottom of the sphere.
>>
>> As a next step, I added a "diffuser" at the origin of the cylinder, 
>> inside the sphere, using a "trans" material for an isotropic 
>> distribution. The readings I get now show the same illuminance value 
>> for every measurement point. This is the script:
>>
>> oconv sky.rad scene.rad ports.rad >> pipe80.oct
>>
>> oconv -i pipe80.oct >> i_pipe80.oct
>>
>> mkpmap -app pipe80.gpm 1000000 100 -t 60 -apc pipe80.cpm 1000000 -apO

>> ./ports i_pipe80.oct
>>
>> rtrace -w -h -I -ab 1 -ad 16384 -aa 0.01 -ar 512 -app pipe80.gpm -apc

>> pipe80.cpm 100 -e errors.rad i_pipe80.oct < points.inp | rcalc -f 
>> rcalc.rad >> data.dat
>>
>> The total luminous flux reaching the diffuser is bouncing from the 
>> cylinder. Is it a problem between the parameters and "trans", with
the 
>> pmap and "trans" or something else?
>>
>> Erico
 
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