Hi,
May I know if I set metalness to 1.0 without changing the use glossiness to use roughness, will Vray still giving the correct result? what is the correct way to use metalness if I am not using PBR textures?
Hi @jackieteh
Use roughness is optional. Glossiness (or its inverse - roughness) controls the overall amount of scattering, depending on the selected BRDF model. i.e. - how shiny it is. If a roughness map is used instead, then you can switch your V-Ray material to use roughness. For more information, please do visit our very detailed blog post on the subject: Understanding metalness
I have read the article you post here, thank you very much.
I try to understand what you have explained here, just want to double confirm:
Do you mean we can use metalness in either glossiness or roughness workflow, with or without textures is it correct?
Yep, if no map is present, simply invert the float amount.
Thank you for your clear and simple answer, straight to the point 
Ahah, easy when the question is simple and to the point! 