when i try to make a certain spot on my model a different type of material i get an outline, any help?
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when i try to make a certain spot on my model a different type of material i get an outline, any help?

What’s the Polycount on that model?
1.3 million
the line gets finer as the polycount increases
Did you fill four model with a base material before you started painting? (click on “M” for material, got to color/fill object)
But regardless, with 1.3 mill Polys you will always get jaggy edges when painting materials. With Color it’s better as it will blur or blend over the vertices, but when you paint materials, every poly has always just one material.
I would separate my mesh in Polygroups and fill those afterwards with the different mats.
Hope that helps.
P.S.: Y que hace ese pablo? 
yes
ill definitely try it out, thanks
just trying to learn