reflection glossiness strangeness

[Guest]

I am currently setting up a scene that has a black metal material on an object. The scene is lit using a dome light and IBL but something strange happens though. The black diffuse is set to 1,1,1 RGB and the glossiness is set to 0.78. However if I set the reflective Colour to 45,45,45. the resulting reflection is as if there was no glossiness at all (there's a very clean reflection like high gloss). The dispersion has completely gone. If I set the reflection to 30,30,30 or 50,50,50 RGB the dispersion of 0.78 glossiness behaves as expected.

It seems if using a reflection range between 40, 40, 40 and 49,49,49 RGB, it causes the error. I am assuming its a bug or error when trying to calculate such a low reflection on a very black diffuse using HDRI as this does not happen when using standard V-Ray plane lights.

I haven't managed to find any one else talking about this so I am not quite exactly what is going on. No pictures yet but I can get some up later today.

[alexyork]

I feel like I've come across this before myself but I can't be sure. I'd be interested in seeing your tests to show this happening.

[Guest]

Images here showing the two reflection differences when changing the RGB value for reflection. Sorry about the images I had to mask out most of it as its confidential. The lighting changes slightly but it still uses the same HDRI and dome light setup.

[instinct]

Try lowering the cutoff of the material. When lowering the reflection color the impact on the final pixel might drop below the threshold and hence be cut off (the sharp line). Wildly shooting in the dark there.

Regards,
Thorsten

[Guest]

I will give it a go, thanks for the tip.