Seriously, you don't need to do that (unless you want to fiddle with 450 different lines to give them different widths). Just go to ShareCG and get the "Poser - a toon outlines render preset for Firefly" freebie. It will give you all the possible lines in a scene. Also, turning on depth-fogging in Comic Book mode makes the ink lines thinner as they recede from the camera, though you need a big mesh landscape to see it.

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Learn the Secrets of Poser 11 and Line-art Filters.