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"Jellby" <me### [at] privacy net> wrote in message
news:l2l### [at] badulaqueunexes...
> Could it maybe be "faked" in some way, similarly to how the caustics
> keyword
> fakes photons?
>
The Pov Reference Manual says under "Language Things that don't work as one
expects":
"
"Can I specify variable IOR for an object? Is there any patch that can do
this? Is it possible?"
Short answer: No.
Long answer:
There are basically two ways of defining variable IOR for an object: IOR
changing on the surface of the object and IOR changing throughout inside the
object.
The first one is physically incorrect. For uniform IOR it simulates physical
IOR quite correctly since for objects with uniform density the light bends
at the surface of the object and nowhere else. However if the density of the
object is not uniform but changes throughout its volume, the light will bend
inside the object, while travelling through it, not only on the surface of
the object.
This is why variable IOR on the surface of the object is incorrect and the
possibility of making this was removed in POV-Ray 3.1. "
I wonder why they kept faked caustics in Pov-Ray when we have photons that
can do it better, and took out surface variable ior leaving us with no
replacement.
--
-Nekar Xenos-
----------------------------------------
"The truth is out there..."
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Nekar Xenos nous apporta ses lumieres en ce 01/03/2006 10:40:
> I wonder why they kept faked caustics in Pov-Ray when we have photons that
> can do it better, and took out surface variable ior leaving us with no
> replacement.
>
>
Faked caustics are way faster and good enough in many situations. A prime example been
the light
play on the bottom of a water body.
--
Alain
-------------------------------------------------
'I can resist anything but temptation.'
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We've all been thinking along the lines of doing it with a statement similar
to media which is very complex. How about something simpler, like
fade_colour? If the ior gets denser at a specific rate like fade_colour
does, will this not make it more feasable to do?
--
-Nekar Xenos-
----------------------------------------
"The truth is out there..."
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"Nekar Xenos" <go_### [at] yahoocom> wrote:
> We've all been thinking along the lines of doing it with a statement similar
> to media which is very complex. How about something simpler, like
> fade_colour? If the ior gets denser at a specific rate like fade_colour
> does, will this not make it more feasable to do?
>
>
> --
> -Nekar Xenos-
> ----------------------------------------
> "The truth is out there..."
The effect of a changing ior is not so much affected by the rate of change
of its value, but its change relative to the direction of travel of the
light ray. In order for it to affect the direction, it needs to interact
with a change in iro along a surface not perpendicular to its line of
travel. So this would require, not only discrete sampling to determine the
ior along the light path, but also some sort of adaptive sampling to
determine an effective angle of incidence for the change in ior. This
would not be entrely impossible, however, it would significantly increase
the calculations and overead involved and probably not give significantly
noticeable results versus what could be faked much more easily.
-tgq
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