Simple Offset of Single Line

[Mark Beattie]

Good day,

 

I was wondering if there was a simple way to offset single 'Pen' lines in Designer (or another process I haven't thought of yet). The Contour tool offsets nicely but treats the single pen line as a shape and offsets it on both sides.

I am trying to achieve something like what's shown in the included photo.

Sorry if this is a duplicate post, but I couldn't find anything else that covered this.

Thanks in advance,

Mark 

[GarryP]

Welcome to the forums @Mark Beattie

If your line only has one dimension – it’s is just a simple closed curve then Contour Tool should only ‘offset’ on one side of the line (unless the line ‘curves back on itself’ somehow).

If you are getting an ‘offset’ on both sides then that would suggest to me that your line is either an open curve or a 2D shape which looks like a line (e.g. an expanded stroke). Check the Layers Panel to see if your layer is a Curve layer or a Curves layer; a Curves (plural) layer will have more than one curve in it. Also, check to see if the curve is open or closed.

In that case there’s probably not much you can do other than remove the inner our outer stroke before or after using the Contour Tool.

If this doesn't help then we may need to see a document containing the curve so we can check it for ourselves before giving further advice.

Edit: Amendments in italic or struck through.

Edited September 18, 2023 by GarryP
Added clarification.

[Aammppaa]

@GarryP Really? I've never seen this one sided behaviour of the contour tool. And the help clearly shows a curve being offset on both sides.

https://affinity.help/designer2/English.lproj/pages/CurvesShapes/contouringShapes.html

So far as I am aware there is no easy way in Affinity at present to offset to one side only.

So, you either need to draw the center line, and offset in both directions, or find some way to mask one side of the offset, or convert the offset to curves (bake) and destructively remove the inner (or outer) half.

[GarryP]

Apologies for the confusion, I was only thinking of a closed curve.
I’ve amended my post above accordingly.

[thomaso]

Though I am aware it doesn't I still happen to expect that the stroke property "Align stroke" would work with open, not-closed curves, too.

A workaround for a not-centred stroke could be using a texture brush that includes a transparent area in its image. Nevertheless, it is not a workaround with the flexibility of the requested stroke offset.

[R C-R]

5 hours ago, thomaso said:

Though I am aware it doesn't I still happen to expect that the stroke property "Align stroke" would work with open, not-closed curves, too.

For some open shapes like in this which side is the inside?.afdesign example (made in V1 so you can open it) I don't think there is a clearly defined inside or outside, so that's probably why it isn't implemented in AD.

[Old Bruce]

6 hours ago, GarryP said:

Apologies for the confusion, I was only thinking of a closed curve.

As you are using Designer you could try using the Appearance pane in Window > Studio > Appearance. Multiple strokes with different widths and different blend modes aligned to Outside, Inside, or Centre can give great results, far better, in my opinion, than what is available with the Offset tool.

[thomaso]

1 hour ago, R C-R said:

For some open shapes (…) I don't think there is a clearly defined inside or outside, so that's probably why it isn't implemented in AD.

If there is no clear in- or outside then I either don't mind or just choose and switch if wanted, regardless whether it is called in the interface "in-/outside" or "left/right" or "top/bottom" or simply "a/b" for instance.

Compare the two directions in closed curves that we occasionally need to toggle for a certain visual result, without being able to determine in advance which direction will be the correct or needed one or which gets assigned when creating an object, (though it seems to be created counterclockwise 'by default', interestingly regardless of the creation direction).

[R C-R]

27 minutes ago, thomaso said:

If there is no clear in- or outside then I either don't mind or just choose and switch if wanted, regardless whether it is called in the interface "in-/outside" or "left/right" or "top/bottom" or simply "a/b" for instance.

So if I understand you correctly you would like an additional 'switch' option or something like that?

[thomaso]

12 minutes ago, R C-R said:

So if I understand you correctly you would like an additional 'switch' option or something like that?

No, an additional 'switch' option is not required nor requested. It would be sufficient if the existing options for stroke alignment would also affect non-closed curve objects.

[R C-R]

14 minutes ago, thomaso said:

No, an additional 'switch' option is not required nor requested. It would be sufficient if the existing options for stroke alignment would also affect non-closed curve objects.

I do not understand how those options would work with curves like the one in my example -- IOW, how would the app know which side the user wants to be considered the inside?] or outside?

Can you explain abit more about how that should work?

[v_kyr]

It's even easy to do with 3 grouped single lines.

[thomaso]

8 minutes ago, R C-R said:

I do not understand how those options would work with curves like the one in my example -- IOW, how would the app know which side the user wants to be considered the inside?] or outside?

I wonder that you don't understand this – but obviously don't get problems to fill such a shape without noticing a conflict of inside and outside fill.

As mentioned above, neither the app nor the user needs to know in advance which side the stroke would get applied, it just starts with one and possibly chooses the other option if wanted. – The result could look like this (… but without the need to simulate it with a texture brush):

[R C-R]

29 minutes ago, thomaso said:

I wonder that you don't understand this

OK, I see what you mean so thanks for the clarification. There is the minor issue of what to call those two Align buttons & possibly a more problematic one to resolve if the shape is subsequently closed or visa versa if a closed curve is opened, but I suppose that could be worked out somehow.

It might be more of a problem with complex open curves that cross themselves multiple times but there is probably a solution for that as well.

EDIT: I think I need to clarify what I mean about problems with this. What I was thinking is that for an open shape like in the example it mighty be natural for users to assume that the 'inside' is the filled part & the 'outside' is the unfilled part. I'm not sure how best it could be clarified in the UI that that isn't possible.

[thomaso]

12 minutes ago, R C-R said:

There is the minor issue of what to call those two Align buttons

Hardly. It doesn't matter how they are called. As we know already Serif had no difficulties to make decisions for misleading terms like "Revert Defaults" (instead of "revert to defaults") or the German "Layoutseiten" (instead of "Druckbögen" = spreads), not to mention unambiguous terms which may have various meanings and need to be understood in their context (e.g. "Studio", "Persona").

23 minutes ago, R C-R said:

a more problematic one to resolve if the shape is subsequently closed or visa versa if a closed curve is opened

No. Like before, just choose one and switch if wanted. If you like a rule I think you can develop one with the start/end point of an open curve and a decision for one consequent side when following the path. (again: compare "direction" of closed curves)

And: just consider how overlapping fills got solved with the "Fill Mode" options: (which, by the way, triggers the question whether "Fill Mode" (aren't "solid", "gradient" or "bitmap" fill modes, too, at least in the understanding of users?) and "Alternate", "Even-Odd", "Winding" and Non-Zero" are useful, helpful, logical, unambiguous, clear and easy-to-understand or even to learn and with predictable assignment)

26 minutes ago, R C-R said:

It might be more of a problem with complex open curves that cross themselves multiple times

More? Here I can't even imagine a problem. (again: if you don't see a conflict with fill then there is none at all with stroke.)

Fun fact: if I choose "Reverse Curves" in this example the stroke jumps to the other side of the curve. (while stroke alignment still doesn't have an affect)