hello,
I am trying to use BSDF data generated from photogoniometer reading . while defing the BSDF material in .mat file.
void BSDF m_bsdf_mat
6 0 data.xml ux uy uz func.file
0
0
the up vector is to be defined. Can I know what does this up vector mean? how does it influence the surface types. does -t -rz -rx -ry effect the defination. how to define an up vector for a sphere/bubble.?
Thank you
Regards,
Shashanka Sunkara
Hi Shashanka,
the up-vector relates to some expected orientation of a fenestration system. The more general meaning is that it defines an in-plane reference direction. Since you are probably refering to measured BSDF that is converted by pabopto2bsdf, and since the default expectation for the pgII gonio-photometer is to have the upward direction of fenestration samples point to phi=0, your up-vector should relate to the phi=0 direction. Talking about conventions, typically the outside surface of fenestration samples are measured pointing at theta=0, which conflicts with the idea that the front (surface normal) of the BSDF surface in a Radiance model points inward. You can use the -t switch of pabopto2bsdf to correct for this. For a sphere, please be aware that you will see the spherical surface under angles close to grazing which cannot be included in your measurement. Probably you will have a dark border surrounding the central region of the sphere in your renderings, unless you "fill" / extrapolate the missing directions by e.g. fitting another model to your data. Other than that, if you have a measured BRDF, the up-vector would orient it on the surface as expected.
Cheers, Lars.
hello,
I am trying to use BSDF data generated from photogoniometer reading . while defing the BSDF material in .mat file.
void BSDF m_bsdf_mat
6 0 data.xml ux uy uz func.file
0
0
the up vector is to be defined. Can I know what does this up vector mean? how does it influence the surface types. does -t -rz -rx -ry effect the defination. how to define an up vector for a sphere/bubble.?
Thank you
Regards,
Shashanka Sunkara
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Radiance-general mailing list
[email protected]
https://www.radiance-online.org/mailman/listinfo/radiance-general
Hello,
Thank you for you responce. can please ellobrate with an simpel example regardning the effect of up vector.
Regards,
Shashanka
On 10/04/18 21:00, [email protected] wrote:
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1. Fwd: Defining UP Vector to BSDF Material
(Shashanka Sri Nagaveera Sunkara)
2. Re: Fwd: Defining UP Vector to BSDF Material (Lars O. Grobe)----------------------------------------------------------------------
Message: 1
Date: Tue, 10 Apr 2018 11:22:05 +0200
From: Shashanka Sri Nagaveera Sunkara
<[email protected]>
To: [email protected]
Subject: [Radiance-general] Fwd: Defining UP Vector to BSDF Material
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"; Format="flowed"hello,
I am trying to use BSDF data generated from photogoniometer reading .
while defing the BSDF material in .mat file.void BSDF m_bsdf_mat
6 0 data.xml ux uy uz func.file
0
0
the up vector is to be defined. Can I know what does this up vector
mean? how does it influence the surface types. does -t -rz -rx -ry
effect the defination. how to define an up vector for a sphere/bubble.?Thank you
Regards,
Shashanka Sunkara
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Message: 2
Date: Tue, 10 Apr 2018 13:32:08 +0200
From: "Lars O. Grobe" <[email protected]>
To: Radiance general discussion <[email protected]>
Subject: Re: [Radiance-general] Fwd: Defining UP Vector to BSDF
Material
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"; Format="flowed"Hi Shashanka,
the up-vector relates to some expected orientation of a fenestration
system. The more general meaning is that it defines an in-plane
reference direction. Since you are probably refering to measured BSDF
that is converted by pabopto2bsdf, and since the default expectation for
the pgII gonio-photometer is to have the upward direction of
fenestration samples point to phi=0, your up-vector should relate to the
phi=0 direction. Talking about conventions, typically the outside
surface of fenestration samples are measured pointing at theta=0, which
conflicts with the idea that the front (surface normal) of the BSDF
surface in a Radiance model points inward. You can use the -t switch of
pabopto2bsdf to correct for this. For a sphere, please be aware that you
will see the spherical surface under angles close to grazing which
cannot be included in your measurement. Probably you will have a dark
border surrounding the central region of the sphere in your renderings,
unless you "fill" / extrapolate the missing directions by e.g. fitting
another model to your data. Other than that, if you have a measured
BRDF, the up-vector would orient it on the surface as expected.Cheers, Lars.
hello,
I am trying to use BSDF data generated from photogoniometer reading .
while defing the BSDF material in .mat file.void BSDF m_bsdf_mat
6 0 data.xml ux uy uz func.file
0
0
the up vector is to be defined. Can I know what does this up vector
mean? how does it influence the surface types. does -t -rz -rx -ry
effect the defination. how to define an up vector for a sphere/bubble.?Thank you
Regards,
Shashanka Sunkara
_______________________________________________
Radiance-general mailing list
[email protected]
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