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MDenham wrote:
>
> 1) the axis of anisotropy
> 2) the "ordinary" axis
>
> It turns into a useful (though limited) form of the otherwise not-gonna-happen
> "variable ior" request thanks to this. (Generalized variable ior isn't going
> to happen for reasons that are mentioned in the documentation, such as
> "pockets" of high IOR - or even not-so-high IOR - having potentially
> pathological behavior. You'd need to switch to a solely
> rays-start-at-light-sources approach - photons, only slower - to make this even
> slightly viable, and that kind of rewrite probably isn't worth it. [If it turns
> out that it's necessary for a "good" spectral system, then we may have issues.
> :-D])
>
Ah, and here I was thinking it was just as simple as tracing a second
refraction ray.
Bummer.
--
~Mike
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> clipka wrote:
>> Hey, get real: You need to press the "shift" key for quite a host of
>> things, I guess. As a German, for instance, I need to press "shift" to
>> get a multiplication asterisk, dividing slash, opening or closing
>> parentheses, quotes etc,
>
> And for all nouns too, right? :)
>
On my side, all the followings need two keys:
\!@#$%?&*()_ (Shift +...)
My Alt Char key is worn smooth...
Alain
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>
> Wondering, is ambient light (global setting) in rgb or just gray ?
>
It's a full rgb value. Whenever you provide only a single float
(ambient_lights 1), it get's promoted to a color vector (ambient_lights
<1, 1, 1>)
Setting "ambient_lights <1, 0.2, 5>" is perfectly valid.
Alain
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> clipka wrote:
>
>>> Maybe that's a part for media, not pigment.
>>
>> Birefringence is definitively neither a media nor pigment thing, but a
>> straightforward interior thing, and would have to join ranks with ior
>> and dispersion (as a matter of fact it's a difference in ior depending
>> on polarization with respect to the "optical axis" of the (AFAIK
>> necessarily) crystalline material).
>
> How hard would it be to implement birefringence ...? Seems like it could
> easily be faked
>
> Syntax would be trivial:
>
> ior 1.5, 1.7 //(birefringent material)
>
> You don't really need to care about the polarization of light, since
> light in POVRay doesn't have polarity anyway.
>
> I would imagine tracing a second ray at a different IOR would be rather
> simple to add.
>
In addition of the second ior, you also need an axis or "direction".
If you take a sphere of birefringent material and make it turn, the
difference in refractions changes. It also changes depending on the
distance from the view axis.
There is a plane where both iors are the same and an axis where they are
the most different, usualy. They are frequently perpendicular, but I
think that there are cases where the axis is not normal to the plane...
I think that you "may" attempt to simulate it. Some experimentation in
view. Some layering and/or averaging would be required.
Alain
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Alain <aze### [at] qwerty org> wrote:
> > clipka wrote:
> >
> >>> Maybe that's a part for media, not pigment.
> >>
> >> Birefringence is definitively neither a media nor pigment thing, but a
> >> straightforward interior thing, and would have to join ranks with ior
> >> and dispersion (as a matter of fact it's a difference in ior depending
> >> on polarization with respect to the "optical axis" of the (AFAIK
> >> necessarily) crystalline material).
> >
> > How hard would it be to implement birefringence ...? Seems like it could
> > easily be faked
> >
> > Syntax would be trivial:
> >
> > ior 1.5, 1.7 //(birefringent material)
> >
> > You don't really need to care about the polarization of light, since
> > light in POVRay doesn't have polarity anyway.
> >
> > I would imagine tracing a second ray at a different IOR would be rather
> > simple to add.
> >
> In addition of the second ior, you also need an axis or "direction".
> If you take a sphere of birefringent material and make it turn, the
> difference in refractions changes. It also changes depending on the
> distance from the view axis.
> There is a plane where both iors are the same and an axis where they are
> the most different, usualy. They are frequently perpendicular, but I
> think that there are cases where the axis is not normal to the plane...
If the "axis" isn't normal to the plane, you're working with something with at
least two axes of anisotropy. (This would be a _much_ harder case to work with.
Uniaxial birefringence is probably doable; trying to write it to handle two or
more axes will result in programmers chasing you with hatchets. :-D)
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