maxxxmodelz opened this issue on Jun 07, 2012 · 636 posts
bagginsbill posted Wed, 13 June 2012 at 11:48 PM
Quote - You want to use Fresnel_Blend on every surface where you do reflection. No exceptions. Skin - walls - everything.
BB - wouldn't that stop the reflections from the light originating from the camera angle reflecting off the skin facing the camera? Or am I missunderstanding this node?
Sorry I'm not answering as usual - really overwhelmed.
The Fresnel_Blend does the Fresnel reflection coefficient calculation. Every surface obeys the math here. Yes, it does decrease the reflections on surfaces that face the observer, but you use a coefficient of 1 with it, not some lesser value that you cast about trying to guess what it should be. .1? .12?, .15? Forget it.
I have been doing the true, exact fresnel calculation for quite a while using many nodes, or Schlick's approximation, or some of my own approximations. Now we have it in a single node.
There are some tricks to using it because real life is not simple. Surfaces that are not smooth do not exhibit the ideal Fresnel effect at a macro level - only super smooth polished surfaces do that. Real surfaces do exhibit perfect Fresnel effects at microscopic levels, but there are so many pits, peaks, and valleys on a surface that the effect is smeared a bit.
I handle this by:
Using a slightly higher IOR than is indicated by the speed of light through the material I'm simulating, or by not using 0 as the inner value.
Using less than 1 for final multiplied reflectivity - usually .5 to .8.
Using softness on the Reflect node
Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)