Trans material and photon map

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

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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--
Dipl.-Ing. Jan Wienold
Project Manager
Fraunhofer-Institut f�r Solare Energiesysteme
Thermal Systems and Buildings, Lighting and Daylighting
Heidenhofstr. 2, 79110 Freiburg, Germany
Phone: +49(0)761 4588 5133 Fax:+49(0)761 4588 9133
[email protected]

In office: Mo,Tue: 9:00-18:00
We-Fr: 8:30-14:00

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

Sorry, wrong thread.

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