PDA

View Full Version : How to control fresnel for dielectric material



djwaterman
09-21-2012, 08:15 AM
I've been using the dielectric material node for glass and car tail lights with interesting results, but how do you control the glancing angle for the reflections? It seems like there's no input for it.

Also, how do you tint its color besides ramping up the absorbtion value. These tests looked fine in isolation but when placed in a scene on a car they seemed too dark.

107998


I thought at least cutting some of the reflection down might help, that's why I'd like to get some fresnel working on it.

OFF
09-21-2012, 08:48 AM
You can use Scalar Layer with incidence angle gradient as input to Refraction Index for control reflectivity.

RebelHill
09-21-2012, 10:07 AM
Nope... Dielectric node is fresnel ready... the incidence>falloff is a product of the IOR. The fresnel is quite evident in your images even... the reflection becomes stronger as the surface turns away from the angle of view. The spec value is the overall specular reflection level. Basically, u set the overall reflectivity via the spec, and turn the ior up and down to control the ratio of front reflection to glancing angle reflection. Low IORs give low face and high glance, high IORs give high face and glancing.

probiner
09-21-2012, 04:25 PM
Have you tried Material Blender from db&w tools? Basically you can replace Shading components or mix them with others. For example you can input Dielectric in Background Material, the put a plain color in Foreground Refraction Shading and change the Opacity to 30%. It will tint the reflections; in an un-natural way, but you get the point.

Therefore you can also replace the Reflection, say by inputing Incidence in a Curve node and then have Beziers draw how the reflection falls off.

Cheers

Tobian
09-21-2012, 05:32 PM
Hmm, yeah as RH says, it's already energy conserving, the reflection glancing and facing should be correct for the Fresnel value you enter in for the type of glass/plastic.

I find Dielectric problematic for tinted plastics/glasses as yes, it's a little hard to control. I tend to just roll my own for stuff like that. Also in Dielectric doesn't allow you do separate the reflection and refraction blur, and doesn't have options to mix up the transparency with some SSS.

It's fairly simple to do materials like that by hand, just mix up reflection and refraction using a Fresnel, and tint the refraction.

djwaterman
09-22-2012, 02:23 AM
Thanks everyone for the information, there's lot's of possibilities to try here. I ended up ditching dielectric and using the normal surface editor layers to build up a look that seemed to have more control. What I liked about the dielectric was the darker colors in the thicker areas of the glass.
But coming back here and seeing the different advice, I'll have to try some of it and see what happens. (I've been getting back into LW after playing around with Maya/Vray and in a sense I'm looking at LW with fresh eyes again, experimenting, learning and trying things in new ways.