fresnel reflection

[bmcaff]

Hi Julian,
Mine are a bit out of date now and there are better shaders out there to do this kind of thing.
I think there is a ctrl_fresnel (search) shader utility which when combined with a dgs in a phenomena or with a normal shader that should do the trick.

[JulianS]

Muchas gracias Brendan.

I will give that i try.

PS: Big fan of your work. :)

[Synthesizer]

I usually just run a sampleInfo's facing ratio into a ramp's v coord. Then connect the out alpha to any shader's reflection spot. I find this to be quite flexible :)

http://img100.imageshack.us/img100/5238/fesnel7ud.th.jpg (http://img100.imageshack.us/my.php?image=fesnel7ud.jpg)

[JulianS]

I fond the ctrl_fresnel, but does anyone knows how to use it, is assign to the texture tab, so should it be use as a texture. =\


http://forums.cgsociety.org/showpost.php?p=2281096&postcount=16

[lazzhar]

Yes just use the connections as shown in Synthesizer's picture. Less hassle especially if you want to render on another computer where the MR shader is not installed and start wondering what's going on.

[bmcaff]

Yes just use the connections as shown in Synthesizer's picture. Less hassle especially if you want to render on another computer where the MR shader is not installed and start wondering what's going on.
Quoted for agreement. For ease of use and control you really can't go far wrong with this method and indeed it's mostly what I use. You just need a little understanding of the properties and the appearance of any given material. On a more general note I usually find that with the exception of glass and glossy transmission maya shaders really do cover almost all the bases.

[francescaluce]

I found the ctrl_fresnel, but does anyone knows how to use it...
Ehya Julian.
If you use also the mix8layer just plug the kr
from the ctrl.fresnel into an opacity slot and
leave the default blending mode as mix. this
if you wanna use two materials, blending them
in a fresnel fashion. if you wanna tweak instead
the property of a mat, if it is scalar plug it straight
to the node, if color, convert it to a color before.


cu soon,
francesca


ps: lazzhar, I took a look at your demoreel rightnow,
damn it is pretty nice. love it.

[Chris-TC]

Quoted for agreement. For ease of use and control you really can't go far wrong with this method and indeed it's mostly what I use. You just need a little understanding of the properties and the appearance of any given material.

I don't agree to this. It's very difficult to achieve real Fresnel reflections using this method.
That's because Fresnel reflections are not linear, they're exponential. Run a google search to see some example graphs.
If you want to simulate these kinds of curves by simply remapping with a ramp you'll need quite a number of points defining that ramp in order to approximate the non-linear Fresnel curve.

P.S.: Francesca, any chance of an XSI version of the Ctrl.Fresnel?

[bmcaff]

Well it's a matter of control really and sometimes what is "correct" may not work for a given scene. There are lots of times where a fresnel function will do but equally so there are others where a slight tweek of the edge or center reflectivity is needed and can be easily done with the Ramp. I also believe that fresnel is not precisely exponetial and it's governed by the fesnel equation. However setting the ramp interpolation to exponetial wil give reasonable results with just 2 or 3 points.

In any case, one or the other methods are valid and it's really down to you own workflow and preference. Depending also on how critical the physical accuracy needs to be.

[floze]

I don't agree to this. It's very difficult to achieve real Fresnel reflections using this method.
That's because Fresnel reflections are not linear, they're exponential. Run a google search to see some example graphs.
If you want to simulate these kinds of curves by simply remapping with a ramp you'll need quite a number of points defining that ramp in order to approximate the non-linear Fresnel curve.

P.S.: Francesca, any chance of an XSI version of the Ctrl.Fresnel?
Just set your ramp to exponential interpolation and it looks quite similar to a 'true' fresnel reflectivity.

My favorite right now is the new mib_glossy_reflection/refraction nodes that come with maya 7. It's quite cool because it has all the stuff built in, like fresnel (called edge factor), distance falloff, multi sampled glossiness, anisotropy and even dispersion (non-physical correct though). It is quite easy to combine the reflection and refraction to get some really nice looking dielectric shader.

Btw: If you're just after fresnel reflectivity, use a standard maya blinn. It features this type of phenomenon, just play around with the Specular Roll Off attribute.

[yolao]

Ehya Julian.
If you use also the mix8layer just plug the kr
from the ctrl.fresnel into an opacity slot and
leave the default blending mode as mix. this
if you wanna use two materials, blending them
in a fresnel fashion. if you wanna tweak instead
the property of a mat, if it is scalar plug it straight
to the node, if color, convert it to a color before.


cu soon,
francesca


ps: lazzhar, I took a look at your demoreel rightnow,
damn it is pretty nice. love it.

can someone explain this a bit more....?

i mean,

-first i connect the ctrl-fresnel with the connection editor in to the mix8layer, i connect the Kr from the ctrl-fresnel to the F_opcaity layer_0.

-then, if i grab the mix8layer node to the reflectivity of the material the connection editor appears.... then what?.... what do i have to connect there??

-also how can i control the fresnel effect?

thanks

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