[Radiance-general] Sampling thorugh TRANS material

[Germán Molina Larrain]

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 <gregoryjward at gmail.com>:

> 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 <germolinal at gmail.com>
>
> *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
>
>
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