Kubuntu 16.04.3 kernel 4.10, AMDGPUpro 17.50 (legacy opecl)
CPU AMD R7 1700
GPU AMD Rx 480 8gb
Worked: using regular glossy shader.
Short description of error
Pricipled BSDF doesn't allow negative colors for its specular part, so when we add the negative principled shader with the positive one it should render a black object but instead, it's only rendering the positive shader.
I tested the diffuse, subsubscattering and transmission parts of the principled shader and only the specular one it's not allowing the negative colors or above 1, in other words only allowing clampled colors between 0 and 1.
Exact steps for others to reproduce the error
- create a material and in this material, create 2 colors, one negative, the other positive
- connect each color to a principled shader
- set the "Metallic" parameter of the shaders to 1 and the "Specular" to 0
- add these shaders
- apply the material to a sphere
- the rendered sphere should be black but it's colored.