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Converting Pencil or Pen Curves into Brush curves

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My wife and I are new to Affinity Designer, so please bear with me as I certainly haven't learned the "correct" terminology, or the names of the menu items, their locations or their options!

Some background:  We are attempting to take my wife's pencil and paper drawings and convert them into closed-shapes in Fusion 360 (an Autodesk CAD program).  Those shapes will then be extruded into bodies and used to "engrave" or develop 3D models that can be either 3D printed or more recently CNC carved into wood.

We purchased Designer, because it can export into SVG, which Fusion will accept (but not always very elegantly!).

We've done some test drawings, and if I draw with the pencil, pen or ellipse tool, I only get a single line in the SVG when imported into Fusion (what I would call a pure path, and NOT a stroke--but that may be terminology from other programs).

After several experiments, it appears that the best workflow is to scan the paper image into PNG, do a bit of cleanup/brightness/contrast modification in a photo editor, and then bring the resulting cleaner PNG into Designer as a reference layer.

We then tried tracing out the main features from the drawing using an Apple Pencil on an iPad Pro, and can only get reasonbly good results using the pencil or the pen.  Unfortunately, when these are imported into fusion, they can't be extruded or used as cut bodies, as they are a single line, and not a closed path-as-if-it were a line.  (I hope that makes some sense!).

I'd really like to find a clean workflow that isn't too time consuming.  My wife is a traditional fine artist, so working on the iPad for her is a challenge.  I'm an engineer and certainly no artist!

Is there an easy way to convert the pencil/pen paths into brush strokes on iPad?  I saw that a similar question to this was answsered on the Windows forum, but it's solution doesn't seem to work on iPad.  

I've tried a LOT of different software packages to make this a reasonable process, but haven't found one yet (I don't have Adobe Illustrator, which might be a way, but I was hoping Designer would be a better solution)--things I've played with: Photoshop, Inkscape, various environments in Fusion 360.

I'd even take a completely better workflow if someone has already solved this in a different way.




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First of all, Inkscape would have been totally able to do this, I used it to make silhouettes later on 3D carved (and/or embossed) in dices (I just use Blender, not Autodesk Fusion 360, but same stuff), and those been produced both as a prototype, 3D printed, and also the prototype, passed to mold injection.

But is not rare to use a tool and not find the "sweet way with it". I just want to mention that is already doable with inkscape, and also with Affinity Designer. Just to provide you with the certainty that it is indeed doable. Of course, I do absolutely everything desktop based, never using a tablet as most software is a bit toy-like compared to what you get in a desktop. Affinity is a bit of an exception to the rule, though. I don't understand the absolute requirement to do this on the iPad, while it is clearly an advanced task, much more flexible to be done in a Windows PC (or even a mac). I mean, almost anyone has access to a PC or mac machine (specially if being an owner of an iPad, as is kind of a luxury/gadget).

You might want to use Inkscape autotrace feature, and then  edit/clean the result. The enhanced contrast of the bitmap, PNG file, is good for getting it to the autotrace thing, as it'll need less settings tune-up, but not really needed if you trace it manually. Which is what I'd do, as anyway, autrace+ cleaning afterwards takes overall surely more time. I can tell you that this is totally possible with both Inkscape and Designer. So, my bet is that you are getting stuck at some point and we don't know which it is... But if is only the "not being a closed path, but a line" once in Fusion, yep, as mentioned, you need to "expand stroke", and then "add" to join all the layers-strokes into one. Then export the SVG. The features should be in the iPad version ( I don't use ipads).

AD, AP and APub.  Ryzen 9 3900X, 32 GB RAM, GTX 1650 4GB, 500GB m.2 SSD, 1TB HDD 7200rpm. Wacom Intuos 4 XL.

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16 hours ago, summersara said:


I think you might need to expand the stroke and then the Boolean operation ‘Add’. Something like this tutorial Blob brush alternative for Affinity Designer it’s for the desktop but the Expand stroke and Geometry are under Edit on the iPad.

 @summersara  YES!  That's EXACTLY what I needed.  It did indeed work as expected when I pulled it into Fusion.  Thanks so much for the pointer!  

@SrPx  I haven't been so successful with Inkscape, but I'm still experimenting.  We got the iPad so that my wife (who is the real artist) can experiment with Digital in an on-the-go environment.  She's a traditional oil painter or pencil-on-paper kind of person, so moving into the world of digital arts is new, and a bit intemidating.  I'm well aware of the typical superiority of desktop/laptop-based tools over tablet tools, but we don't yet have Affinity on any of our PCs, we have both Mac and Windows laptops and a main Windows Desktop, so I haven't made the dive into buying it for all the platforms (Hint Hint--Hey Serif, make a Mac+Windows+iPad discount license option).  And yes, the expand stroke and add are on the iPad version :-).

@DM1  Well, no not exactly, but that is an interesting feature that I might just have to go use!


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20 hours ago, PhilK said:

She's a traditional oil painter or pencil-on-paper kind of person,

I was that too, I just can't remember when (literally :D ...probably in 1991....although not really... I made my first pixel art (computer graphics, old style) for games back in around 1985 (Spectrum 48k "computer" ) but I painted with pastels and pencils, back then). No,  hehe, seriously, my main message was/is that it is the type of task that can be done well with both vector apps mentioned. I would think that the main issues would be indeed to produce kind of perfect curves instead of wobbly lines (if the sketches are rough or fast), and for that, IMO, the best way would be just to import the scanned pencil drawing (like your PNG that you mentioned) with the raw pencil drawing into Affinity Designer, as a reference layer, make a vector layer over it, pick the node tool "pen" (neither brush), and trace over node by node (instead of using the brush or the pencil) , managing the nodes handlers to get your perfect curves (if u made one of those "connect the dots" things (those drawing templates) as a kid, you'll know what I mean. Although of course, unlike in those things, you don't set the dots and later the curves,  you set a node, then the following curve, handle the nodes to refine the curve and control how affect  the previous curve, plant the next node, etc. But joining the dots with curves, not straight lines, by using the node handlers to get the precise curve each time). This shall ensure that the shapes to carve are perfect and look professional.  So, there's no need to deal with brush painting or anything. INDEED, I'm recommending this path as the fastest and more error free. Also, good for 3D!! As you generate less weird profiles that can produce wrinkles in your extruded 3D shape later.  You want perfect curves, few nodes, as also are easier to control. You don't need to loose accuracy nor detail by using as fewer nodes as possible.

You don't even need to change the contrast or levels in the scanned image, always that you scanned the image even minimally decently, as you only need to see  in the reference layer where the pencils lines go, and go making (tracing) your nodes (dots, like control points), and handling the long curves (or short, more points when small detail is needed...also useful to know how to change independently the handles, for when you need a sharp angle, etc) between them. Tip about this : Less is better. Usually, I would use the less nodes possible to express the shape accurately. But never leaving out a detail that is indeed a detail, and not a doodling excess or some pencil dirt. of course, this would be better done by the artist, as knows better how she wants her lines (maybe you could teach her how to use the app and  the tool, first), and it is often as styling stage, like it is traditional inking. I believe this is equally doable with Designer in your iPad, Inkscape or Designer in the Windows laptop that you have, or Affinity Designer in your mac, if you ever purchase the other platform versions.

It is also key what @summersara  explained very well and I blatantly repeated. To be sure to "expand stroke" and use "add" to merge all shapes. Or how DM1 did in the ipad. As you need the shape to be solid (not a line) and closed shapes so that a manifold compliant 3D app (like surely Fusion 360 is, as tend to be all 3D printing apps) can actually do something with those shapes in the SVG imported. Like carving, etc.

AD, AP and APub.  Ryzen 9 3900X, 32 GB RAM, GTX 1650 4GB, 500GB m.2 SSD, 1TB HDD 7200rpm. Wacom Intuos 4 XL.

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