Hi all,
I am trying to generate a BSDF of a profile angle symmetrical textile. The
problem is that the BSDF is supposed to be left and right symmetric (as is
the geometry). In practice the BSDF doesn't look left/right symmetric in
BSDFviewer. Is it a problem due to the ray-tracing calculation with many
small objects or did I mess up something? here is the command I have run
to generate the BSDF :
genBSDF +f +b -geom millimeter -n 5 0.rad > 0.xml
I attach the 0.rad file used to the email. Thanks in advance for your
help!
Sincerely,
Marouane Boudhaim.
0.rad (91.9 KB)
Hi Marouane,
Your fabric has very thin lines in it, which may be difficult to integrate with the normal sampling density. Since the pattern seems to repeat, I recommend that you restrict your sampling area using the genBSDF -dim option to set a bounding box. Looking at your file, the pattern appears to repeat every 42 mm. You can set a square area near the middle of your fabric with this diameter like so:
genBSDF +f +b -geom millimeter -dim 1500 1542 1500 1542 -1 0 0.rad > 0.xml
This seems to produce something reasonably symmetric when I try it.
Cheers,
-Greg
···
From: [email protected]
Date: June 23, 2017 7:25:25 AM PDT
Hi all,
I am trying to generate a BSDF of a profile angle symmetrical textile. The problem is that the BSDF is supposed to be left and right symmetric (as is the geometry). In practice the BSDF doesn't look left/right symmetric in BSDFviewer. Is it a problem due to the ray-tracing calculation with many small objects or did I mess up something? here is the command I have run to generate the BSDF :
genBSDF +f +b -geom millimeter -n 5 0.rad > 0.xml
I attach the 0.rad file used to the email. Thanks in advance for your help!
Sincerely,
Marouane Boudhaim.
Hi Marouane,
I am not the best to answer this, but as I struggled recently with this, here
is my cheat sheet (also maybe someone could check it whether it is really OK).
You need to set up the genBSDF options and rfluxmtx parameters according to
your geometry. Seems like the default set up was insufficient for your
geometry.
-ab n
ambient bounces - according to material reflectance
p^n - should be less than 5 %
-c
number of rays per incident patch - Klems - means 145 patches
the resulting transmission flux is averaged per patch
depends on bsdf model tensor or Klems
number of rays per hemisphere - tensor
-t3|4 n
tensor 3rd or 4th rank
3rd for isotropic - 2^(2*n) - result for c
2^n - resulting patches - means transfers to angle resolution
(2^n)*(2^n) - incident and leaving
4th for nonisotropic - 2^(4*n) - result for c
2^(2*n) - resulting patches - means transfers to angle resolution
(2^(2*n))*(2^(2*n)) - incident and leaving
nmax = 7 - correspods to angle resolution < 2°
-ad n
ambient division
number of daughter rays spawned at each ambient ray intersection
contingent on the ray weight being above the lw setting
-lw
limit weight
minimum weight of a ray being traced
at a ray intersection of n ambient division rays are spawned the weight of each
of those rays is 1/(n* the diffuse reflectance of the intersected material)
-st
treschold for specular sampling
if the specular reflection of transmission of a material is below this value,
specular sampling will not occur
should be less than specular reflectance of material (rs)
rs^2 - will include secondary reflections
Kind regards,
Paulina
···
On Fri, 23 Jun 2017 07:25:39 -0700 [email protected] wrote:
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Message: 1
Date: Fri, 23 Jun 2017 16:25:25 +0200
From: [email protected]
To: [email protected]
Subject: [Radiance-general] Non symmetrical BSDF from symmetrical
geometry
Message-ID:
<OF074179BA.FD10BA4F-ONC1258148.004CAE43-C1258148.004F3B41@ise.fhg.de>
Content-Type: text/plain; charset="us-ascii"
Hi all,
I am trying to generate a BSDF of a profile angle symmetrical textile. The
problem is that the BSDF is supposed to be left and right symmetric (as is
the geometry). In practice the BSDF doesn't look left/right symmetric in
BSDFviewer. Is it a problem due to the ray-tracing calculation with many
small objects or did I mess up something? here is the command I have run
to generate the BSDF :
genBSDF +f +b -geom millimeter -n 5 0.rad > 0.xml
I attach the 0.rad file used to the email. Thanks in advance for your
help!
Sincerely,
Marouane Boudhaim.
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