Converting a dash into individual strokes.

[Doc Ricky]

Hi, hoping for some help. I’d like to convert a dashed stroke on a curve into individual curves. Not an expand stroke, per se, as that will result in a series of closed shapes. Much simpler, just individual curves. Is there a technique for this? 

I am using using affinity designer on the iPad. 

[Dan C]

Hi Doc Ricky,

Welcome to the forums

The best way to do this is to select the curve, go to the three dot menu at the top left and select Expand Stroke, then without removing your selection, go to the same menu and select Divide under Geometry. This will create multiple 'curve' objects, one for each dash. Hope this helps!

[gdenby]

Him Doc Ricky,

First, a question. Why do you want a bunch of open curves? I can think if a few reasons, one of which is related to a post from a user a few weeks ago, The user needed open curves so a laser cutter would only travel along many hundreds of open curves. From what I could learn, the cutter's RIP software couldn't handle clipping shapes. What would your use be?

And I should say that I did my work on my desktop. While I really like my iPad, I'm old enough that my fingers can't handle gestures well, or even touching the right spots. So what I did was on my desktop. I've done enough work w. the iPad that I think the same results would be possible for folks w. better tactile and visual abilities.

To get to your query, yes, there are ways to get what you want, but in this case, they are anything but quick and easy.

I've been working off and on for the last few weeks to come up w. a routine that was not too tedious to produce open lines. The base problem is that Designer works w. areas, and by default Designer's boolean operations create closed shapes. Certain shapes can be made so that booleans produce line sections that can be fairly easily separated and cleaned up, and leave the interior strokes.  But I was working at the opposite of what you are looking for. The skills I had developed for isolating the lines were much less effective for producing something like a  regular dotted stroke.

I'm attaching a image that shows various attempts I did today.

Most show very irregular dashed lines. I couldn't find a series of ad hoc shapes that would divide the letter outline evenly. Designer at this point will only propagate a vector along a path that is a font. I did a search, and found a font that was geometric shapes. Unfortunately, the simple circle was a filled shape. So while it was easy to propagate it along a "path to text path", when I subtracted those from the base letter, it produced many hundreds of fragments. Best results, but wa-a-y too much time cleaning up bits. 

[Doc Ricky]

Indeed, I am looking for the creation of a number of open paths, not closed shapes, which is what the Expand Stroke and Divide solution would provide. And yes, I do intend to use the vector image as a way to guide a plotter into the area, so closed shapes won’t work. I wish I could use vector arithmetic to open up shapes or use shapes to cut up open paths. Maybe those will help. 

[gdenby]

Hello again, Doc Ricky,

I understand, you need data for a plotter. I've been working on a tutorial for separating out open vectors, but have becomes somewhat bogged down trying to work thru how the "join curves" operation works. But here is a brief description of what you might try it if you want dashed lines from a letter shape. It requires manual work, and in many cases is time consuming.

***

Here is a method for producing open curves as dashed lines indicating a shape. It can be pretty easy if the shape is simple, and mostly vertical and/or horizontal lines. Complex shapes like alpha-numerics become harder as they become more elaborate.

Make the shape, no fill, dashed stroke made of either butt or square cap type. Set the stroke to either inside or outside. Play with the dash setting to get as close as possible to desired. (With very tight curved letters, this may produce oddly shaped dashes as they round the curves or angles.)

Expand stroke. This will produce a "curves" object. With the curves selected, enter node mode, and select all. Use the "break curve" tool. This will decompose all of the mostly rectilinear shapes into individual open lines. There will be many hundreds of simple vector lines  Most likely, the bottom most layer will still be labelled "curves. Hide that for now.

Go back to move/select tool, and start drawing marquees around the curve shapes that are not at the original shape periphery.

NOTE: It would be really good to have a lasso tool for this, but a marquee is all that is at hand now. 

Delete those selections. Hide what is left, and then show the "curves" layer. Go into node tool mode, and pick out any fragments that are not part of the original periphery. Delete as selected.

There may be some problems w. the curves remnants. It appears they are closed shapes that are formed from just 2 nodes.

Show all. There may be some odd fragments that need to be tweaked manually. Apparently, the break curve routine can shatter the expanded strokes in unexpected ways.

***

As noted above, getting all the little dashes requires more selecting than isolation lines that cross the shape boundry. But maybe this will help to do what you need.

Attached, a sample starting w. a rounded rectangle. The base took me about 8 minutes on my desktop. The subsidiary lines, a few seconds each. I did try the same using my iPad. Because I am still quite a novice using that, I had passable results, but the work was much slower. The delays don't seem to be w.the hardware, just the operator.

[Doc Ricky]

Wow, this is going to be laborious as heck. Maybe there's a way to use the original shape as a "mask" to pick out the extra nodes. 

[gdenby]

If you subject any of the bits to another boolean operation, it just repeats the creating more closed shape issue. The earlier poster who was using a laser cutter could not use clipping curves. I believe (don't trust my recollection) there was a response saying that different software RIPs did recognize clipping, and so nesting the desired lines within a parent object would work. 

Just now, the most straight forward method is manually grabbing the unwanted stuff. The rounded rectangle ended up w. about 160 curve sections,  so at least 640 bits  to start out. The ones  horizontal and vertical took less than a minute. The  sections along the curves were hard to grab. 

And again, having myself done several hundred curve separations, the dashed character is about as hard as it gets. Filling a letter w. something like shading strokes is much easier.