Re: Fresnel effects -- plugin tool 2004-01-20 - By nospam2
Back
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)
To unsubscribe send a message to
Carrara-unsubscribe@(protected)
Yahoo! Groups Links
To visit your group on the web, go to:
http://groups.yahoo.com/group/Carrara/
To unsubscribe from this group, send an email to:
Carrara-unsubscribe@(protected)
Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
|
|
