Is a PBR material still considered PBR if you change Roughness values to make it look better?

Ninb

I'm asking this because I see a lot of tutorials online that make materials from scratch in Substance and  Quixel and in the process the put roughness values or play with the roughness slider to make the material fit their model.
Thanks in advance.

ActionDawg

Is a block of rough steel still steel if you polish it to a mirror finish?

poopipe

Yes, it's what you're supposed to do.

Roughness is a fudge.  The maths used for roughness are an approximation and there are several different methods in popular use - all of which differ slightly.

FULGORE

Definitely.
"PBR accurate" roughness values are useful as a base, but these values can never account for the damage/stains/dust/polish/whatever has happened to the material in the context of how you've used it

sprunghunt

Even in live action films there will be staff who go around spraying dust on surfaces to reduce glare or wetting surfaces to make them shinier. It's not realistic but it makes the scene look better. 

eg: 
https://parade.com/101364/marilynvossavant/wet-streets-in-movies-20/

Andreicus

I think that what really matters is the end result, you are making art not a simulation for NASA.

Put your mesh with the material applied to it in a scene that is properly lit, for example a scene with an HDR global light and ask yourself "does it look good ?" and "Does it look the way i want it to be ?" 

If the answer to both questions is "Yes" then you are ready to go. There will be always cases where you must tweak the material values to achieve a certain look, especially with stylized stuff.
The only thing to remember is to avoid total black or total white materials, for all the rest is ok to tweak the parameters.