PDA

View Full Version : BSDF, nodes and IOR



Pavlov
07-02-2013, 04:01 AM
Hi,
i think i've asked this before but i didnt get there yet.
Question is: how do you guys manage to control Delta/Sigma nodes ?
A common BSDF node should control Fresnel (change of transparency and reflection at 0 and 90) with index of refraction. I.e. Maxwell's materials are like this, and they are incredibly powerful.
We still seem to be forced to use gradients, which are fake.
Does someone knows a smart setup to manage the entire fresnel thing (both transparency and reflection change) with a simple IOR value ?

thanks in advance
Paolo

RebelHill
07-02-2013, 04:07 AM
use the fresnel node.

Pavlov
07-02-2013, 04:24 AM
I did, but what if you have other nodes plugged into Delta's specular ? Multiplying the outputs of previous node flux with Fresnel keeps the physical accuracy of IOR, or is there a better way to "insert" Fresnel node into the flux ?

Thanks,
Paolo

Pavlov
07-02-2013, 04:33 AM
And again, question is: normally i can chose a specularity of 30%. This means material is 30% reflective and 70% diffuse. If i plug Fresnel node in specular, behavior changes with incidence, but i'm not able to set a starting reflection level anymore.
Does IOR imply automatically that reflection amount is managed by incidence ? Again, Fresnel node seems to output something different from the value i put in, like if it precalculates something. How does it work exactly ?

thanks
Paolo

RebelHill
07-02-2013, 05:35 AM
The IOR controls the % of reflection. You dont set any "base" amount (strength of reflection)... fresnel IOR represents the strength of reflection at different angles of view.

Pavlov
07-02-2013, 05:39 AM
So its the common fresnel curve, which ranges from 0 to 100% and change the in-between values.. thanks, i should have thought of it :)
Paolo

RebelHill
07-02-2013, 05:56 AM
Well no... it ranges from x to 100%. What x is (and the rate of change across the angles) is determined by the materials IOR.

Pavlov
07-02-2013, 07:36 AM
Ah. Interesting, i assumed minimum value was 0, and jumped to high values fastly with high IOR values.
Maybe IOR curve display in FRYrender, when it still exhisted, fooled me :)

thanks
Paolo