Last night I discovered a really strange little quirk in Illustrator’s Appearance panel. Effects applied to a stroke can behave differently depending on if they were applied to the stroke by creating it with the stroke selected in the Appearance panel, or by adding it to the overall path itself, then dragging it onto the stroke. I have, I think, been vaguely aware of this subtlety for a while but I finally sat down and did some experiments to nail it down.
Sometimes the roughen effect is applied to the underlying path before the stroke is drawn. Sometimes it’s applied to all of the paths you’d get if you expanded the stroke after the stroke is stretched along the underlying path, resulting in a much messier and erratic look. And you can’t tell just by looking at the Appearance panel; there is no visible difference between a path where the effect was directly added to the stroke (and thus applied before the stroke is drawn) and one where it was added to the base path, then dragged into the stroke (and thus applied after the stroke is drawn).
This persists across a save, too. There’s something Illustrator’s setting in there that it’s not exposing.
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I also tried fooling with Astute’s new “Architect” plugin, which is designed to create sketchy lines that look like an architectural rendering, but is also useful for just generally creating some extra chaos. I’ve been running up against this “sometimes it runs on the underlying path, sometimes it runs on the art stretched along the path” while playing with it. I think the set based on the art brush makes it really clear which ones are operating on the path before the stroke is applied, and which ones are operating after – I’d had an intuition that it happens at a slightly different place in the rendering order than most of AI’s native effects, and this confirms it.
There are very few native effects that create a lot of extra paths this way; one of the few that does behaves differently. Honestly I’m not sure what I expected out of the extrude/bevel effect but I feel surprised that having it at the very top of the Appearance stack makes the path completely vanish.
I should probably try it on the Scribble effect – one of the other few stock effects that can turn one path into multiple paths under the hood, instead of just altering a single existing path – but I feel like I’d need to make a slightly different test case and that’s enough for before breakfast.
Anyway. That’s your dive into deep Illustrator obscurities for today.