Subtracting a shape from a line only works in some cases in Affinity -- why?

[devoured_elysium]

Hi,

I have a bunch of related questions:

I'm designing a Graph. I'm trying to have two nodes connected through an arrow. Something like this:

This curved arrow was actually created by me some days ago. I tried to achieve the same result today and unfortunately I couldn't reproduce it.

At the time, I made the arrow connect the centers of the E and C nodes, and then I added a circle top the of E node, using that circle to subtract from the curve. I did a similar process with the C node. The reason I did this is because for the arrow to look nice, it really needs to have its source and target points be E and C nodes' center points, otherwise it looks ugly (is there a better way of achieving this, btw?) Anyway, at the time it worked fine.

Today I tried the same with a straight line but it failed -- the line disappeared. From searching the forum, the reason seems to be linked to Affinity's inability to subtract shapes from curves. By some reason, if I curve the line:

it then kind of works:

but this is not really what I want! I don't want this to form a closed path! How can I avoid it?

And why does it behave like this only after I've curved the lines?

 

Thanks

[gdenby]

Hi, devoured_elysium,

My understanding is that the boolean operations work on areas. A straight line has no area, so there is no operation. If the line is curved, it implies an area between the nodes. Then the bollean works, but it automatically closes the previously implied area. The new perimeter needs to be cut apart using the node tool.

[devoured_elysium]

Hi. But I could do this work perfectly the other day (as the first picture atests!). Somehow it must be possible? Or am I getting crazy? I can't for the sake of my life reproduce this today.

So, asked in another way: what would be the best way to create a (curved or non-curved) arrow-line that connects two nodes, while making sure that while both ends of the arrow start / stop at the border of the nodes, their trajectories are such as if they were coming from / to the node's centers? In Gravit Designer I would create the two nodes, create the arrow going from the center of one node to the center of the other and then use the knife tool. How can I do something similar with Affinity?

[G13RL]

Hi devoured_elysium,

Another solution would be to add a knot on the arrow at the intersection with the circle and "Break Curve" at that point and then delete the portion of the curve inside the circle.
Repeat for the other end.

Otherwise, for Boolean operations between curves and shapes, the curves must be transformed into shapes by "Expand Stroke" before proceeding. 

[devoured_elysium]

Arghh!! That sounds home! Now that you talk about it, that's most likely what I did the other day.

 

Thanks!

[G13RL]

You're welcome!

[Pšenda]

6 hours ago, devoured_elysium said:

that's most likely

Just look with the Node Tool to see if it's still a single line or a double stroke.

[Thomahawk]

Subtract does not even work correctly with areas only. In this case, I want to subtract the inside of the letter e, but after subtract, the blue part disappears, and instead of a hole, it is all black.

 

[Move Along People]

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[GarryP]

Also, how is the blue part of your letter ‘e’ created?
You may need to Divide the shapes before Subtracting.

[G13RL]

Once the letter is converted to curves, "Layer", "Geometry", "Separate Curves", "Subtract".