Sometimes you will be handled such corrupt mesh where some of the primitives are flipped and a simple Normal sop wont fix it for you, you might not see it in viewport but when rendering you will see dark spots near those areas.
So the solution is pretty simple you only have to apply a :
-Facet sop.
-Tick the Orient Polygon option.
Particle Skull
2018-10-01 11:17:59 +0000 UTC