I’m trying to render some hair in its own render layer and, as you can see in the accompanying picture, the alpha channel comes out with some aliased pixels, making it difficult (if not actually impossible) to composite. I cannot find out why is that happening, does anyone know? Thanks!
I’ll answer my own question, looks like this happens when Primitive is set to Curve Segments in the Cycles Hair Rendering section of the particle settings panel. Setting the primitive to Line Segments seems to solve the issue.