Hi,
if I create a Vray material from a Rhino plaster material than the fresnel reflection can’t be enabled anymore. Attached an example object with plaster material. Looks like there is an internal, invisible parameter which avoid the fresnel effect.
-Micha
VrayMtlFromRhino.zip (111 KB)
Hello @Micha ,
Thank you for posting.
What you have shared is expected, because the Refraction IOR is set to 1 in Rhino for this material type, and to 1.6 in V-Ray Generic material by default.
If you enable Refraction IOR and change it to 1.6 you will get the same results and vice versa if you set Refraction IOR to 1 in V-Ray Generic material the result will correspond to what you have with Rhino Plaster material.
Ah, interesting. No what users expect, but technical logical. So the user can fix the issue.
Since the plaster refraction IOR is set to 1 because it is not needed for the Rhino display and I suppose so it could be any other value it would be nice, if the V-Ray conversation would ignore the 1 and set it to a physical correct value. It’s strange to enable fresnel reflection and don’t see any reflection or fresnel IOR 1. From an users view a pitfall. 
Or can’t the V-Ray plugin see the material type? I could ask the McNeel team to set proper values and not reflection IOR 20 and refraction IOR 1.
V-Ray takes only parameters into consideration when converting, not the material type itself.
If you do receive McNeel comments on that please post it here as well afterwards.
