Both will work, Mapping node work not only with the UVMap but with vectors too and to the same but in one node.
Open Decal2.blend and try it.
EDIT: Found what the issue was, If an Image texture has “Clip” set then it won’t shade outside the clipping bound, it needs to have “Repeat” set for a Mapping node to work. However that messes up scale (as it now tiles) so in the case of Decals, the method I have used seems to be the only choice.
Blend file attached for anybody else interested.
Attachments:
You must be
logged in to view attached files.
