There was a script already that did this but it doesn't work correctly with MultiSub Materials it'll just instanced one and repeat it on all materials within it. Would like to get a script that would convert all materials in the scene whether they are separated materials or multisub instanced ones.
Forum topic · Scripts Wanted
Convert Normal Bump to VrayNormal Map
By TwilightZoney · 2016-07-17
Description
Comments (2)
barigazy · 2016-07-19
Bug fixed. Try new version 1.6 http://www.scriptspot.com/3ds-max/scripts/convert-normal-maps
fajar · 2016-07-19
may be you could contact the poster of those script (barigazy)...