Expand stroke on self-intersecting curves to create knotwork/interlace

[Lindsay Wilson]

I've recently been playing around using a combination of expand stroke and the shape builder tool to create interlacing knotwork designs. It's very powerful for this, but I'm running into a problem with self-intersecting curves. Take a look at the attached screenshot.

Simple case first. I have multiple separate curves (A). Expand stroke gives (B). Then shape builder to give (C).

Now, a single self-intersecting curve (B). If I do expand stroke directly on this (E), the crossovers are all welded together and the outline of the stroke isn't visible. Hope that makes sense.

To get it to work, I have to split the curve into parts (F) so that each part is NOT self-intersecting. Then expand stroke gives (G), with the intersections fully visible, and shape builder gives the final result (H). 

This is alright, but there are situations where it is not easy. Either in a large knotwork, where it's hard to keep track of what goes over/under what, or if I have applied a variable-width stroke to the curve, in which case splitting it messes up the stroke widths (I posted another topic on this). I would really like to be able to just go directly to a fully-outlined curve, i.e. I want to go straight from (D) to (I).

Maybe this just isn't possible - neither Inkscape nor Illustrator do this either - but if there's a way I'd really like to know about it!

[NotMyFault]

A workaround:

 

prepare once:

1. Create a 360x180 rectangle no fill no stroke
2. duplicate
3. add fill white, stroke black, 8px to inside
4. nest filled layer to infilled layer
5. stretch layer to cut off left and right stroke
6. export as png
7. create new image brush using png

For curves:

1. assign brush to your curve. Use appearance panel to set blend mode to darken or multiply.
2. duplicate curve
3. use node tool, reverse curve,

now you have an outline you want.

[Lindsay Wilson]

@NotMyFault Very neat idea - I wasn't aware of how to use the image brushes! Unfortunately, while that produces the _appearance_ of the lines, they're not usable vectors.

[NotMyFault]

5 hours ago, Lindsay Wilson said:

@NotMyFault Very neat idea - I wasn't aware of how to use the image brushes! Unfortunately, while that produces the _appearance_ of the lines, they're not usable vectors.

You are right. I had the wrong impression that shape builder would work for both vector and pixel layers, which i s not the case. Sorry for my  failed attempt.

[DWright]

There is no method to achieve this result with a single operation in Designer and you will need to use multiple operations to achieve this 

[fjunk]

I (thought) I came up with a nifty idea of just Bezier Curving the gaps and then using Shape Builder.

That didn't work:

As you can see, having lined up the edges of the newly created squares as nearly to seamless as I could discern, Shape Builder still doesn't join them as intended.  I tried in three different programs to try to find a simple, straightforward way to fix this.

No dice.

See for yourself.  Maybe I'm missing something.  Seems like more work than it oughta be.

Update:  Nevermind. Selected the whole thing then used Layer / Expand Stroke. That fixed it. After that, it worked as intended.

pretzel_WIP_AFD2.afdesignpretzel_WIP_AFD2.afdesign