Dear all,

 I am learning to use the POV.
I'd like to konw the IOR in interior related to the calculation of
Fresnel coeff. either in POV or MegaPOV.
I'd like to know whethers the calculation is done in a rather specific
condition, for example, requiring the use of photon-mapping(please
ignore my incorrect use of the term) or just generally used calculation
method in POV.
I'm not sure this question fits this group.
Thanks.

Sun

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In article <39AD832F.5E469EB6@shinbiro.com>, sjk### [at] internetzonecokr 
wrote:

> I'd like to konw the IOR in interior related to the calculation of
> Fresnel coeff. either in POV or MegaPOV.
> I'd like to know whethers the calculation is done in a rather specific
> condition, for example, requiring the use of photon-mapping(please
> ignore my incorrect use of the term) or just generally used calculation
> method in POV.

Angle-dependant reflection using the fresnel equation is only available 
in MegaPOV right now. The ior value used is the ior you specify in the 
interior. Photon mapping is not required for angle-dependant reflection.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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Thank you, Chris.
 I just gave it a try using MegaPOV following Nathan's instruction.
I am really glad that the images look nice. What I did was to use the basic
scene  supplied by POV program with spheres.
 I prepared three spheres of different IOR's(1.05,1.6, 2.35) and set the
reflection_type, reflection_min, reflection_max, and conserve_energy, blinn
in the finish statement. Also I prepared the plane with blue/white checkered
pattern having almost same reflection_type, ..., conserve_energy, blinn and
IOR of 1.8.
 When I changed the camera position from high to low(simply by changing the
y-axis height, approaching grazing angle), the reflecting intensity of the
spheres on the plane(floor) look increased(I am not definitely sure but it
seems like). I am not sure my observation of the image is correct or not.
Anyway, I really like the result.
On top of that, the higher the IOR value, the larger the reflection intensity
on the sphere.

   I've had a chance to browse the SIGGRAPH 97 Conference Proceedings by
E.P.F Lafortune, K.E.Torrance, et al. titled "Non-linear approximation of
Reflectance Functions", Annual conference series, pages 117-126(ACM SIGGRAPH,
Addison Wesley, Aug. 1997).  The paper says "The glossy reflection on the
table disappears at grazing angles, which is exactly the opposite of real
surface behavior, when the classical cosine lobe model was employed, for
various viewing angles.(in Figure 5)"
  Would it be O.K. to call my ray-tracing attempt using the MegaPOV
reflection_type, reflection_min, ... , a kind of viewing angle dependent
ray-tracing as depicted in the Lafortune's paper?

Thanks.

Chris Huff wrote:

> In article <39AD832F.5E469EB6@shinbiro.com>, sjk### [at] internetzonecokr
> wrote:
>
> > I'd like to konw the IOR in interior related to the calculation of
> > Fresnel coeff. either in POV or MegaPOV.
> > I'd like to know whethers the calculation is done in a rather specific
> > condition, for example, requiring the use of photon-mapping(please
> > ignore my incorrect use of the term) or just generally used calculation
> > method in POV.
>
> Angle-dependant reflection using the fresnel equation is only available
> in MegaPOV right now. The ior value used is the ior you specify in the
> interior. Photon mapping is not required for angle-dependant reflection.
>
> --
> Christopher James Huff
> Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
> TAG: chr### [at] tagpovrayorg, http://tag.povray.org/
>
> <><

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