Convert pie to curves

[JariH]

What am I doing wrong here... Or is this a bug? How to create a round cap line from a pie shape?

• Create a single-line Pie shape (Circle - Convert to Pie - Hole radius 100%) with rounded caps.
• Convert to curves (probably not necessary).
• Expand strokes - round caps disappear.

Any advice, please? The workaround is to create this shape by modifying the curve with node tools. To get precise angles a pie shape would be a better option, but...

[Pšenda]

24 minutes ago, JariH said:

What am I doing wrong here

A pie is a closed shape, in your case the distance between the two sides of the curves is zero, so they are drawn over each other - try using the Node Tool to move one node. You must therefore break the closed curve (Break curve) and delete the excess nodes. Then expand stroke.

 

In this case (as in the given link) it would help if Affinity indicated the type of curve (different icons for open and closed curve in the layers panel).

 

Edited January 11 by Pšenda

[Aammppaa]

The problem is that your process creates a closed shape that has nodes on top of nodes.

Try dragging on of the central 2 nodes before you expand the stroke, and you'll see what I mean.

Here's an alternative approach...

1. Draw your pie and set the angle you want, but don't increase the hole size.

2. Convert to curves.

3. With the node tool, hold Ctrl (on Windows, check status bar on Mac) and click the 2 line segments you don't want.

4. Expand the curve.

 

 

 

 

 

[Pšenda]

55 minutes ago, Aammppaa said:

The problem is that your process creates a closed shape that has nodes on top of nodes.

However, it is still a "bug" that the identical topology of nodes is displayed correctly once - i.e. with a rounded cap, and with Expanded stroke, the curves change completely.

[JariH]

Thanks for the tips here.

I need to break the curve at both endpoints - This way the round caps are retained when converting to a shape.

(Or create the shape with the "Spiral Tool" - but this was far too complex as well...)

I was expecting more intelligent behaviour than possible. There really should be a one-step solution to merge overlapping points on a curve. This goes to my wishlist.

[Pšenda]

1 hour ago, Pšenda said:

However, it is still a "bug" that the identical topology of nodes is displayed correctly once - i.e. with a rounded cap, and with Expanded stroke, the curves change completely.

The problem/bug isn't whether the curve is closed, but that the handles of the overlapped nodes have the same direction and the same length.

 

Edited January 11 by Pšenda

[lacerto]

Related, but a bit off-topic: expanding a stroke can deviate from what is seen on canvas also in diverse situations where stroke parameters are somehow extreme or untypical (e.g. abrupt smart nodes with bevel joins). In these kinds of situation rasterizations typically give what is rendered on screen while expanding gives what will happen when the stroke is exported to vectors (in OP's case the opposite is true: exporting to vectors retains the visual rendering).

expanded.pdf

It is also interesting to compare how different apps do expanding. E.g. in VectorStyler the resulting shape at least in auto-expanded strokes can be dependent on current zoom level (accuracy of rendering on canvas). In CorelDRAW (2023) expanding strokes often causes distorted shapes. Illustrator (CS6) appears to outline paths generally as rendered but similarly as Affinity apps struggles with untypical node type + attribute combinations and might produce three different versions (when rendered as stroke on canvas, expanded, and stroke exported as vectors).