Corner rounding on expanded paths?

[Lorox]

I just watched this https://www.instagram.com/heyadamdesign/reel/DEaGGAhNbVd/ short video showing a demonstration of how to easily round corners to appear visually correct on expanded objects in Illustrator – i.e. avoiding visually (obviously) clashing radii on outer and inner paths.

Unfortunately this doesn't work in Affinity as it does in AI although you seemingly do corner rounding in quite the same way.

Anybody got an idea how to do this correctly in Designer (or Publisher) as well? That is, of course, without doing all the math you theoretically could do to determine the proper radius to each of the paths according to the thickness of the (visual – here: black) outline...

[GarryP]

I don’t think what you want to do is possible with just the Corner Tool because every selected node must be given the same Radius when you start dragging, which doesn’t give the result you want.

I’d be happy to be proven wrong though.

Maybe there's a different route which can be taken that doesn't involve maths.

[thomaso]

Visual workaround with two circles as helper objects:
(unfortunately without any snapping at the required edges)

[GarryP]

I was messing around with this and I came up with another way to do it, without using maths, but it’s a bit fiddly and only works in Designer.

If you know the thickness of the original rectangle then you can:

1. draw a circle with the same thickness (aligned to the inside) to the required size;
2. expand the stroke of the circle;
3. select both shapes;
4. use the Shape Builder Tool to create a new shape which only uses the parts of the shape you select.

See attached video.

I’m not wholly convinced that the result is absolutely perfect but it might be good enough for most purposes.

[Lorox]

4 hours ago, GarryP said:

...but it might be good enough for most purposes

I guess so – and it can obviously be done real quickly with rectangular corners.

As with non-rectangular cornes on more complicated forms it seems advisable, though, to wait with expanding until everything is actually shaped as it should finally appear while maintaining a "real" stroke. Keeping an expanded stroke of a more complex appearance in uniform width when making changes to individual anchor points of its inner and/or outer paths can really be a pain in the butt...

As a matter of fact I try to not forget to keep "building forms" for construction with "regular" strokes on one or more separate layers and then work on duplicates of these forms for further elaborations including expanded versions. Always better to have something to come back to than possibly having to start from scratch.

Nevertheless I wonder why that technique shown for Illustrator as shown in https://www.instagram.com/heyadamdesign/reel/DEaGGAhNbVd/ actually works in AI. Looks like in that case the radius applied to the outer path in the first step – say r1 – is sort of maintained before by dragging with the Corner Tool it is (just) increased by the same value as is set (by the very same dragging) for the radius for the inner path – say r2 – which in step 2 is starting at 0. (As it should be when considering the paths being/becoming parts of concentric circles)

In Affinity, though, both of the radii seem to get the same value in step 2 (as GarryP pointed out) – to be precise: the inner radius does not start at 0 while dragging with the Corner Tool in step 2 but is immediately set to the value which has before (in step 1) been applied to the node of the outer path. This is effectively pushing inwards the center of the inner circle in relation to the position of the outer circle making them non-concentric and accordingly making the thickness of the expanded stroke vary…

Did Adobe's developers just do the math better or why can't we do it in Affinity as easily (and correctly)?

Edited January 7 by Lorox
typo

[thomaso]

7 hours ago, Lorox said:

In Affinity, though, both of the radii seem to get the same value in step 2 (as GarryP pointed out) – to be precise: the inner radius does not start at 0 while dragging with the Corner Tool in step 2 but is immediately set to the value which has before (in step 1) been applied to the node of the outer path.

Is this indeed the behaviour in Affinity V2? – To me in V1 both radii get set to 0 in step 2 with both nodes selected, means the previous step 1 gets reset and useless.

[GarryP]

14 hours ago, Lorox said:

Did Adobe's developers just do the math better or why can't we do it in Affinity as easily (and correctly)?

I don’t use Illustrator so I don’t know how it works but it’s possible that there’s an option for users to say whether they want it to work differently, for example either all the same radius or with radii that are relative to the ‘key node’, or something like that.

I guess the best option currently is to not expand the stroke until after the corners have been added. Maybe not practical in some cases but something that could be planned for.

[Lorox]

8 hours ago, thomaso said:

Is this indeed the behaviour in Affinity V2? – To me in V1 both radii get set to 0 in step 2 with both nodes selected, means the previous step 1 gets reset and useless.

Yes, I have V 2.5.6 and this is how I observe it to work. The radius set for the corner node of the outer path in step 1 is kept and assigned to the corner node of the inner path immediately when entering step 2. There is no resetting to 0.

[thomaso]

1 hour ago, Lorox said:

Yes, I have V 2.5.6 and this is how I observe it to work. The radius set for the corner node of the outer path in step 1 is kept and assigned to the corner node of the inner path immediately when entering step 2. There is no resetting to 0.

Oh, there are both ways working:

• If the object has no stroke assigned then step 2 starts with the radius of step 1 for the inner node.
• If the object has a stroke assigned then step 1 gets reset and both nodes start with radius 0.

This appears odd, – why should a stroke influence this (or any) behaviour of the Corner Tool?

[Lorox]

14 minutes ago, thomaso said:

This appears odd, – why should a stroke influence this (or any) behaviour of the Corner Tool?

Indeed! It seems, though, that in both cases the final result will be the same: both radii will eventually – and regrettably – be set to same value…

[thomaso]

2 hours ago, Lorox said:

Indeed! It seems, though, that in both cases the final result will be the same: both radii will eventually – and regrettably – be set to same value…

The two facts that there are two different behaviours while none of them leads to the wanted result – radius set one after the other, as in AI – might point to one or two bugs and possibly worth a thread in the V2 bug reports forum.