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Hi there
if I define an ior value of say 1.5 for an object, but also state in finish
reflection{0.1, 0.8} how does pov ray calculate the reflection? Does it
calculate the proper Fresnel reflection at the angle of incidence based on the
ior value, or does it vary it between 0.1 and 0.8 ?
Thanks
Stu
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> Hi there
>
> if I define an ior value of say 1.5 for an object, but also state in finish
> reflection{0.1, 0.8} how does pov ray calculate the reflection? Does it
> calculate the proper Fresnel reflection at the angle of incidence based on the
> ior value, or does it vary it between 0.1 and 0.8 ?
>
> Thanks
> Stu
>
>
If your reflection block state reflection{0.1 0.8}, then, the reflection
follow a linear variation from 0.1, for a perpendicular ray, to 0.8, for
a tangential ray.
In this case, the ior have NO effect at all.
The fresnel model and equation is not used.
To use the fresnel model, you need to explicitely enable it:
reflection{ 0.1 0.8 fresnel }
This enable the use of the fresnel model and demand that the ior been
set within an interior block.
In this case, the fresnel model is used, then, the result is adjusted to
fit within the provided range.
Next, add conserve_energy if you have any transparency at all.
Alain
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Thanks Alain , that's a very clear description.
regarding transmission that results from using conserve energy: does it matter
what value for t I use in color grbt<> vector or does pov ray simply calculate
a value that is totally independent of t, that is an angle dependent value based
on the calculated reflectance?
stu
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Am 30.04.2015 um 08:07 schrieb Crippso:
> Thanks Alain , that's a very clear description.
>
> regarding transmission that results from using conserve energy: does it matter
> what value for t I use in color grbt<> vector or does pov ray simply calculate
> a value that is totally independent of t, that is an angle dependent value based
> on the calculated reflectance?
The t (transmit) value still does matter indeed; if e.g. you set
transmit to 0.5, you get only 50% of the transmittance you would get if
you set transmit to 1.0.
So if for example the reflection is 20% at a given angle, and you set
transmit to 0.5, the effective transmittance at that angle will be
(100%-20%)*0.5 = 40%.
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