Hello everyone,
I have a question about trans material... The story is the following:
1. I already read what Axel Jacobs has to say about Trans, read the
Radiance Reference Manual and also Googled a bit.
2. After all that, I found out how to model Fabric materials using Trans
(I need some uncolored specular transmission and a bit colored Diffuse
transmission). After the research, I noticed that Trans, as I wanted to
model Fabrics, would only work for gray textiles... but that is good enough
for me.
3. I managed to do all that, and actually run genBSDF to check if the
diffuse and direct parts were OK.... they came very close, but not quite
perfect, even if my parameters were pretty high.
4. Assuming it was as good as it would get, I continued with my
simulation... I am using rcontrib's 2-phase method, with "-ab 12 -ad 4096
-aa 0.1" parameters... but I get some NOT SMOOTH results. LINK TO PICTURE
<https://drive.google.com/file/d/0B2NfkTSl19hQSF9rbTF4S0tMWXc/view?usp=sharing>
Any hints on the parameters I have to use in order to model this product
well? Is this caused by the fact that there is no direct light in the
calculation of the DC matrix? Will my approach work?
Regards,
Germán
Hi Germán,
I'm really only guessing, but I would say you need to increase your -ad value (a lot) to get a good result for your workplane in this situation. You have the noise of the BSDF on the window to filter, which requires a great many samples. Setting -ab 12 is probably higher than needed. What is your -lw setting? This is important for determining the number of rays actually traced. Also, -aa gets set forcibly to zero by rcontrib, since it doesn't support the ambient cache. Try:
-ad 20000 -lw 2e-5 -ab 5
to see if this produces smoother results.
Cheers,
-Greg
···
From: Germán Molina Larrain <[email protected]>
Subject: [Radiance-general] Sampling thorugh TRANS material
Date: March 4, 2016 12:33:12 PM PST
Hello everyone,
I have a question about trans material... The story is the following:
I already read what Axel Jacobs has to say about Trans, read the Radiance Reference Manual and also Googled a bit.
After all that, I found out how to model Fabric materials using Trans (I need some uncolored specular transmission and a bit colored Diffuse transmission). After the research, I noticed that Trans, as I wanted to model Fabrics, would only work for gray textiles... but that is good enough for me.
I managed to do all that, and actually run genBSDF to check if the diffuse and direct parts were OK.... they came very close, but not quite perfect, even if my parameters were pretty high.
Assuming it was as good as it would get, I continued with my simulation... I am using rcontrib's 2-phase method, with "-ab 12 -ad 4096 -aa 0.1" parameters... but I get some NOT SMOOTH results. LINK TO PICTURE
Any hints on the parameters I have to use in order to model this product well? Is this caused by the fact that there is no direct light in the calculation of the DC matrix? Will my approach work?
Regards,
Germán
Thanks, Greg... It worked. Is there any special thing about TRANS that
requres so many ADs? This is the first time I have required a value that
high to converge.
Best,
···
2016-03-04 22:35 GMT-03:00 Greg Ward <[email protected]>:
Hi Germán,
I'm really only guessing, but I would say you need to increase your -ad
value (a lot) to get a good result for your workplane in this situation.
You have the noise of the BSDF on the window to filter, which requires a
great many samples. Setting -ab 12 is probably higher than needed. What
is your -lw setting? This is important for determining the number of rays
actually traced. Also, -aa gets set forcibly to zero by rcontrib, since it
doesn't support the ambient cache. Try:
-ad 20000 -lw 2e-5 -ab 5
to see if this produces smoother results.
Cheers,
-Greg
*From: *Germán Molina Larrain <[email protected]>
*Subject: *[Radiance-general] Sampling thorugh TRANS material
*Date: *March 4, 2016 12:33:12 PM PST
Hello everyone,
I have a question about trans material... The story is the following:
1. I already read what Axel Jacobs has to say about Trans, read the
Radiance Reference Manual and also Googled a bit.
2. After all that, I found out how to model Fabric materials using
Trans (I need some uncolored specular transmission and a bit colored
Diffuse transmission). After the research, I noticed that Trans, as I
wanted to model Fabrics, would only work for gray textiles... but that is
good enough for me.
3. I managed to do all that, and actually run genBSDF to check if the
diffuse and direct parts were OK.... they came very close, but not quite
perfect, even if my parameters were pretty high.
4. Assuming it was as good as it would get, I continued with my
simulation... I am using rcontrib's 2-phase method, with "-ab 12 -ad 4096
-aa 0.1" parameters... but I get some NOT SMOOTH results. LINK TO
PICTURE
<https://drive.google.com/file/d/0B2NfkTSl19hQSF9rbTF4S0tMWXc/view?usp=sharing>
Any hints on the parameters I have to use in order to model this product
well? Is this caused by the fact that there is no direct light in the
calculation of the DC matrix? Will my approach work?
Regards,
Germán
_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general
Hi Germán,
The default -lw setting for rcontrib is actually just 0.002, which means that at most 500 rays will be sampled in the initial scattering, no matter what -ad is set to. You really need to adjust these settings in tandem when the irradiance cache is turned off, as it must be for rcontrib.
Illuminating the interior via a BSDF material means that you are randomly sampling something that is also randomly sampling, so you have two major contributors to variance. You can see some of these effects in my 2011 Radiance Workshop talk, "The Bidirectional Scattering Distribution Function as a First-class Citizen in Radiance":
http://www.radiance-online.org/community/workshops/2011-berkeley-ca/presentations/day2/GW5_BSDFFirstClass.pdf
Best,
-Greg
···
From: Germán Molina Larrain <[email protected]>
Subject: Re: [Radiance-general] Sampling thorugh TRANS material
Date: March 9, 2016 10:32:22 AM PST
Thanks, Greg... It worked. Is there any special thing about TRANS that requres so many ADs? This is the first time I have required a value that high to converge.
Best,
2016-03-04 22:35 GMT-03:00 Greg Ward <[email protected]>:
Hi Germán,
I'm really only guessing, but I would say you need to increase your -ad value (a lot) to get a good result for your workplane in this situation. You have the noise of the BSDF on the window to filter, which requires a great many samples. Setting -ab 12 is probably higher than needed. What is your -lw setting? This is important for determining the number of rays actually traced. Also, -aa gets set forcibly to zero by rcontrib, since it doesn't support the ambient cache. Try:
-ad 20000 -lw 2e-5 -ab 5
to see if this produces smoother results.
Cheers,
-Greg
From: Germán Molina Larrain <[email protected]>
Subject: [Radiance-general] Sampling thorugh TRANS material
Date: March 4, 2016 12:33:12 PM PST
Hello everyone,
I have a question about trans material... The story is the following:
I already read what Axel Jacobs has to say about Trans, read the Radiance Reference Manual and also Googled a bit.
After all that, I found out how to model Fabric materials using Trans (I need some uncolored specular transmission and a bit colored Diffuse transmission). After the research, I noticed that Trans, as I wanted to model Fabrics, would only work for gray textiles... but that is good enough for me.
I managed to do all that, and actually run genBSDF to check if the diffuse and direct parts were OK.... they came very close, but not quite perfect, even if my parameters were pretty high.
Assuming it was as good as it would get, I continued with my simulation... I am using rcontrib's 2-phase method, with "-ab 12 -ad 4096 -aa 0.1" parameters... but I get some NOT SMOOTH results. LINK TO PICTURE
Any hints on the parameters I have to use in order to model this product well? Is this caused by the fact that there is no direct light in the calculation of the DC matrix? Will my approach work?
Regards,
Germán
Very cool. Thanks a lot, Greg!
···
2016-03-09 16:06 GMT-03:00 Greg Ward <[email protected]>:
Hi Germán,
The default -lw setting for rcontrib is actually just 0.002, which means
that at most 500 rays will be sampled in the initial scattering, no matter
what -ad is set to. You really need to adjust these settings in tandem
when the irradiance cache is turned off, as it must be for rcontrib.
Illuminating the interior via a BSDF material means that you are randomly
sampling something that is also randomly sampling, so you have two major
contributors to variance. You can see some of these effects in my 2011
Radiance Workshop talk, "The Bidirectional Scattering Distribution Function
as a First-class Citizen in Radiance":
http://www.radiance-online.org/community/workshops/2011-berkeley-ca/presentations/day2/GW5_BSDFFirstClass.pdf
Best,
-Greg
*From: *Germán Molina Larrain <[email protected]>
*Subject: *Re: [Radiance-general] Sampling thorugh TRANS material
*Date: *March 9, 2016 10:32:22 AM PST
Thanks, Greg... It worked. Is there any special thing about TRANS that
requres so many ADs? This is the first time I have required a value that
high to converge.
Best,
2016-03-04 22:35 GMT-03:00 Greg Ward <[email protected]>:
Hi Germán,
I'm really only guessing, but I would say you need to increase your -ad
value (a lot) to get a good result for your workplane in this situation.
You have the noise of the BSDF on the window to filter, which requires a
great many samples. Setting -ab 12 is probably higher than needed. What
is your -lw setting? This is important for determining the number of rays
actually traced. Also, -aa gets set forcibly to zero by rcontrib, since it
doesn't support the ambient cache. Try:
-ad 20000 -lw 2e-5 -ab 5
to see if this produces smoother results.
Cheers,
-Greg
*From: *Germán Molina Larrain <[email protected]>
*Subject: *[Radiance-general] Sampling thorugh TRANS material
*Date: *March 4, 2016 12:33:12 PM PST
Hello everyone,
I have a question about trans material... The story is the following:
1. I already read what Axel Jacobs has to say about Trans, read the
Radiance Reference Manual and also Googled a bit.
2. After all that, I found out how to model Fabric materials using
Trans (I need some uncolored specular transmission and a bit colored
Diffuse transmission). After the research, I noticed that Trans, as I
wanted to model Fabrics, would only work for gray textiles... but that is
good enough for me.
3. I managed to do all that, and actually run genBSDF to check if the
diffuse and direct parts were OK.... they came very close, but not quite
perfect, even if my parameters were pretty high.
4. Assuming it was as good as it would get, I continued with my
simulation... I am using rcontrib's 2-phase method, with "-ab 12 -ad 4096
-aa 0.1" parameters... but I get some NOT SMOOTH results. LINK TO
PICTURE
<https://drive.google.com/file/d/0B2NfkTSl19hQSF9rbTF4S0tMWXc/view?usp=sharing>
Any hints on the parameters I have to use in order to model this product
well? Is this caused by the fact that there is no direct light in the
calculation of the DC matrix? Will my approach work?
Regards,
Germán
_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general