Split a variable-width curve and preserve stroke weights

[Lindsay Wilson]

Suppose I have curve and have used the pressure curve to apply a variable-width stroke, a feature which I find extremely useful. Now I want to cut/split/break the curve. When I do this, Affinity assigns the same stroke pressure curve to each of the new curves, instead of preserving the correct weights on either side of the cut. Hope the screenshot below makes sense.

Now, in this particular case, I could expand the stroke first of all, then split it. However, this is part of a larger question, and I really need to keep it as a stroke!

Is there any way to get it to automatically assign correct stroke weights to the new curves as shown?

[GarryP]

I don’t think there’s a way to do this without expanding the stroke first, as you said.
However, I’d also be interested to know if it is possible.

In the mean time, one question I have is: “How would the software know how much ‘gap’ to put between the two curves?”
On other words, if you cut the curve with the Knife Tool you get two curves which ‘meet’ at the ends, so you would need to move one end of one curve which would mean that the relative sizes at the nearest-to-each-other ends would no longer ‘match’ in relation to the original curve (if you know what I mean).

[Lindsay Wilson]

@GarryP I only moved the lines apart in the drawing so they were more visible - it doesn't need to make a gap. Calculating the required line widths would actually be very easy - see example below. If the original line went from 100% to 25%, and it was split exactly in the middle, then the new segments should go from 100% to 62.5% and 62.5% to 25% to match up. Just in linear proportion to how far along the line was split.

[GarryP]

If you don’t want a gap, why are you splitting the curve if the process of splitting it would result in the two parts, together, looking the same as the single curve before the split?

Would you be able to supply a visual example of where you think this would be useful?

[Lindsay Wilson]

@GarryP It's wrapped up with making knotwork interlaces using expand stroke and the shape builder. I have another post on the topic, link below. If you have a self-intersecting curve, then expand stroke does not correctly produce fully-outlined intersections that shape builder can then use. The only way I can currently get it to work is by splitting the curve, so each piece is NOT self-intersecting, then doing expand stroke + shape builder on them. However, if my original path has a tapered stroke, splitting it screws up the widths, hence why I'm wanting to do this splitting thing.

 

[GarryP]

Ah, I see, thanks for the explanation.