VRayMtl refraction affects shading even set to black color

[freed-kenneth]

Is it a bug or not that black refraction color contributes some reflection to the render?

Below is the sample of the problem:
The two pictures have the same reflection settings: White reflection color with 1.6 IOR fresnel reflection. Glossiness 0.9, Metalness 0.0

The brown color shading: Black refraction color with 1.01 IOR

The brown color shading: Black refraction color with 1.6 IOR

You can barely see some reflections added to the second picture.

3dsMax version : 2020.1
Vray version : 4.20.01

[hermit.crab]

Mind checking if you have the Fresnel IOR locked (L icon) to the Refraction IOR? That would explain the affected reflections since the value would be taken from the Refraction IOR you changed. Try unlocking the Fresnel IOR and see if that makes a difference, however, note that it is more physically accurate to lock these values.

[tanya_to]

Hello! When "Fresnel reflections" is enabled, the reflection strength becomes dependent on the viewing angle of the surface and on the index of refraction as well.

[freed-kenneth]

Hello! When "Fresnel reflections" is enabled, the reflection strength becomes dependent on the viewing angle of the surface and on the index of refraction as well.

Thanks. This is the answer I need.