Hi everyone!
I have a question about Fresnel calculation in nested dielectrics. Referring to the Fresnel equation and Snell's law a ray travelling from one media to another with the same IOR, to put it simply, should not be bended and reflected (as Specular component). It's the similar situation when sphere with IOR =1 is illuminated inside a vaccum
(in our case meaning empty scene wiht ball and light). In case if there is small difference between IORs, say 1.4 to 1.45, the reflection should be barely visible.
I used this tool for tests:
https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html.
Now in Maya I have created a simple scene with light and two spheres and I noticed that the result is different.
Inside sphere has a strong specular reflection.
Transparent Sphere Mtl: StdSurface, Specular=1, SpecularRoughness=0, IOR = 1.4, Transmission 1
Orange Sphere Mtl: StdSurface, Specular=1, SpecularRoughness=0, IOR = 1.4
Nested Dielectrics = On
Arnold 7.0.0.3
Is this related to different implementation of this phenomenon or is it the result of tracing optimization or scene settings?
Please correct me if I'm wrong.
Thanks
I presume you have set the correct standard_surface.dielectric_priority?
Yes, higher number for the orange sphere, lower for the outer. I also tried reversing this priority and disabling nested dielectrics in settings, but without success. I saw that the dielectric priority can be set only when transparency is enabled, thats why I started to wonder if it's implemented for transmission rays only.
Transmission works as expected, with two the same transmissive shaders (same IOR) there is no bending, but still strong specular.
I will check this behavior in HtoA.
Ok, in HtoA the situation looks the same.
Interestingly in Mantra, specular looks as expected, but only if the inner sphere is full transmissive.
I aslo tried in Maxwell and I think it produces the correct results.
Ok, apparently this is a known issue and we are working on a fix. Thanks for reporting.
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