 | | | Re: Fresnel effects -- plugin tool | Re: Fresnel effects -- plugin tool 2004-01-21 - By pmiinalainen
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You can easily use the fresnel plugin to fake some other properties
as well. I don't think neither rendering engine or materials in
carrara model the real world accurately enough. The 'fake fresnel'
is more like roll-off mixer which can be used to make effects like
fresnel effect.
You can also use it to fake indirect lighting (tint the color to
background's color) or for similar applications. This is often
necessary as true indirect lighting is too time-consuming for
animations.
Simulating reality often demands modeling more that is visible. If
plugin or any other means helps me to have convincing (not absolute
simulation of reality) results, i will gladly use them.
As carrara's materials don't have different channels for shininess
and smoothness /roughness, it is next to impossible to render some
things you see in real world.
One example of things impossible in carrara is reflection fall-off
based on distance between reflected objects and reflecting surface.
In real world reflection dimms and/or blurs as the distance grows.
In carrara the the surfaces reflect always the same amount unless
you make a hand-painted fall-off map. So, i don't think carrara's
rendering engine/ materials are up to the task as simulating reality
just by telling that this is light and this is glass. Let alone,
that shaders are applied to surfaces and are not volumetric. This is
the case with majority of 3d software and has produced thousands of
ways to fake some phenomenons.
Hope to see fall-off plugin soon!
petteri
--- In Carrara@(protected), nospam2 <nospam2@(protected)> wrote:
> Hello m3d242,
>
> >> What's called the Fresnel effect is in fact nothing but another
way to
> m> describe the refraction indice of the material.
>
> m> That's incorrect. The Fresnel effect and the index of
refraction are not the
> m> same thing.
>
> See my just previous post.
> The Fresnel effect is not the same thing than refraction, true :
it is a consequence of refraction.
> It is the result that sinus being bounded by -1 and +1, at low
angle the ray cannot enter the material having an higher refraction
indice and then is totaly reflected instead of being partly
reflected and partly refracted.
> SInce Carrara takes refraction into account, how is it that it
cannot produce the Fresnel effect ?
>
> What I mean is : to calculate the Fresnel effect, one only need
the light ray angle of incidence and the refraction indice of both
material (air and water for example).
> Since Carrara already knwos all that, I don't see the point for an
extra plug-ins.
>
> >> Since refraction is one of the shaders channels in Carrara, I
do'nt see why
> m> the effect would not be rendered by the rendering engine.
>
> m> The Fresnel effect is the roll off of transparency to
> m> reflectivity (or reflectivity to
> m> transparency) on the surface of an object depending on the
viewing angle.
> m> The index of refraction takes into account how light bends (or
refracts) when
> m> passing through and object. The index of refraction has noting
to do with how
> m> reflecive an object is.
>
>
> What you call the roll off of transparency to reflectivity is not
a property per se. It is just a consequence of the refraction law.
> In the absolute, a transparent object could have a zero
reflectivity indice and still produce the Fresnel effect.
> If you look at this imaginary object straight from the top, you
see through it. Then as the angle of vision get smaller (=
tangential to the object surface), at some point you would stop
seeing through it (this property is used in the optical fiber).
> That is the Fresnel effect.
>
> Of course, in the reality, all objects have some reflection
property. SO, obviously, at the angle when there is no more
refraction, all the light is reflected.
> that is why the Fresnel effect is associated with reflection in
people minds. But it is a consequence of the refraction law, not the
reflection law.
>
>
> --
> Best regards,
> nospam2 mailto:nospam2@(protected)
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