I've been following this Lee Griggs' tutorial for Toon Hatching in Arnold, as follows
He uses the UberNoise.osl as a mask color.
But for some reason I'm only able to contour the geometry, the hatching doesn't work whatsoever, although the OSL used seemed to be compiled alright.
I got this error // Warning: [mtoa] Could not link aiOslShader1.outValue to aiToon1.mask_color. and I think it has something to do with it.
I'm using Maya 2019 MtoA 184.108.40.206.
Sorry I don't know how to explain this in more detail, I'm really just following the tutorial.