easy rendering for Rhino in Windows
The basic fresnel effect in NXT will increase the reflective of an material as you view the surface at higher glancing angles. You can see the efect in this article:
You can use this to increase the polished clear finish of a material. Do this by increasing fresnel.
Or you can decrease fresnel for certain materials that need very low reflectance, say a rubber tire. With rubber I use a very little gloss reflection and turn down fresnel so the reflection does not increase at a glancing angle.
The limitation with the basic fresnel is that the basic reflectivity will be increased. There are materials that change color at high reflective angles. In this case, you would not use fresnel, but use an angular blend material in NXT. Iridescent materials might be a candidate for this.