A base for various hatching and "newsprint" halftone filter effects.
Complex in inkscape's filter editor but easy to render, zooming doesn't lag.
If I could capture the structure behind would upload it as well, as it has a nice pattern.
It is based on the lightness values of the source object.
Maybe if there will be a decent filter editor in inkscape I'll get back to it and split the rgb channels instead.
But for now this filter is a bit too complex for the current editor.