Reflection on Specular materials

[Proupin]

Some time ago Octane introduced fresnel reflection; for glossy materials when 'index' approaches 1, if higher than 1, the fresnel effect gets much stronger, and 'specular' controls the overall reflection intensity.

It seems that for specular materials, this same parameter, index, controls Index of Refraction as well as the fresnel effect, which is ok... but even when 'specular' is set to 0 (no reflection), reflection becomes apparent again as soon as there is some transmission (transparency). So, transparency appears to bring reflection back to the material.

Is this expected? I would assume that 0 specular behaved like, well, no reflection, whether the material has some transparency or not. When the transmission is set to 0, the material acts like a regular glossy material, losing its reflection entirely if 'specular' is set to 0.

(I brought up the 'index' parameter as it is the main difference from 2.58, my build of reference for comparission). Attached are two mini-renders, both have the same material with specular set to 0. In the 2.58, the index being around 1.64 in both cases. The beam goes through the glass, and this doesn't reflect any light... in the most current 1.10, we can see the light reflecting everywhere.

[bepeg4d]

hi, what about v1.11 and above?
they have done big changes in the specular material with the fake shadow option and the new medium system.
i'm a big fun of specular material, so if you could share the ocs, i would like to give it a try
ciao beppe

[Proupin]

hi bepeg4d,

Thanks for the interest. I didn't try the non-release builds after 1.10, I just have and, still, refractive objects still reflect even with specular set to 0... but I am uploading the scene so maybe you can pull it off with the newer features