Divide operation

[shedthings]

Hi,

just using the trial license to checkout Designer and hit a problem with the divide operation.

I'm trying to divide a line where it's intersected by a circle but when I do the divide operation the whole line just vanishes - not just visually but no longer listed in the layer pane.

What I'm I doing wrong please?

 

Before I click the divide button

 

After I click the divide button. The Ellipse has changed to a Curve and the original line (curve) that I was expecting to be divided into 2 curves has gone.

 

[Pšenda]

Boolean operations works only with closed areas.

 

Your example would be called dividing by zero:-)

[shedthings]

Ah thanks Pšenda that make sense. 

Any idea how I can acheive this then as I need to create multiple lines starting from the center and going beyond the radius then delete the parts that are inside the circle - i.e. I want to create minute marks around a clock face.

[Alfred]

31 minutes ago, shedthings said:

I want to create minute marks around a clock face.

 

Instead of starting with the Ellipse Tool, use the Cog Tool. You’ll find that it’s very adjustable, so although it’s designed to allow easy creation of gearwheels you can actually use it to create a set of unconnected thin ‘cogs’ for your minute marks.

[shedthings]

Thanks I'll give that a try

 

[Pšenda]

Draw circle. Draw first minute marks. Show Rotation Centre. Move it to circle center.

 

Copy minute mark (Ctrl + C, Ctrl + V), change Rotation to 30°.

 

Ctrl + C, V, Rotation to 60, 90, 120, ......

[shedthings]

Ah wow, thanks really appreciate your time showing me that.

[Alfred]

Instead of copying, pasting and rotating the pasted copy, you can duplicate the first mark with Ctrl+J on Windows (or Cmd+J on a Mac) and then rotate the duplicate. This will allow you to use the ‘Power Duplicate’ feature, whereby subsequent use of the keyboard shortcut will result in the same amount of rotation being applied to each new duplicate.

[R C-R]

1 hour ago, Pšenda said:

Boolean operations works only with closed areas.

Actually, they work on open paths too, but only if an open path defines an area -- IOW, not all of a path's nodes are in a straight line. So for example:

The Divided result actually has 3 curves but I forgot to select all of them for the screenshot so only one red node is shown.

[firstdefence]

10 hours ago, Alfred said:

Instead of copying, pasting and rotating the pasted copy, you can duplicate the first mark with Ctrl+J on Windows (or Cmd+J on a Mac) and then rotate the duplicate. This will allow you to use the ‘Power Duplicate’ feature, whereby subsequent use of the keyboard shortcut will result in the same amount of rotation being applied to each new duplicate.

and to merge psenda & Alfreds input, angle is constrained to 15º increments by pressing the Shift key as you rotate.

 

Tick Tock, lets make a clock 

 

[Pšenda]

9 hours ago, R C-R said:

Actually, they work on open paths too,

 

Exactly - no.

Before operation open area is closing (this can be done by the user by connecting the endpoints of an open curve with a straight line) - and then the operation are done with "closed areas" :-)

However, your example would be helpful (it should be in Help), it is much more clear than a textual description of the operations.

[R C-R]

1 hour ago, Pšenda said:

Exactly - no.

Before operation open area is closing (this can be done by the user by connecting the endpoints of an open curve with a straight line) - and then the operation are done with "closed areas" :-)

The result of a boolean operation may be one or more closed paths, but that does not mean that open paths need to be closed prior to the operation. All that matters is the area enclosed by the paths, exclusive of any stroke they might have. In this respect it is similar to how fills are applied to open curves:

Booleans even work on invisible paths with neither strokes nor fills. If they have dissimilar fills or strokes, the boolean applies the fill & stroke of the bottommost path to the result.

[Alfred]

1 hour ago, R C-R said:

The result of a boolean operation may be one or more closed paths, but that does not mean that open paths need to be closed prior to the operation.

 

@Pšenda was simply pointing out that open paths are always closed (automatically by the program if not manually by the user) before a Boolean operation is performed.

[gdenby]

The way I've come to think of the booleans is that they work with areas, implied, or explicit w a closed shape. So straight line vectors fail because there is no area under them.  Any visible stroke is only something "painted" onto the vector, and defines no area unless created by the "expand stroke" routine.

[lepr]

.

[R C-R]

1 minute ago, Alfred said:

Pšenda was simply pointing out that open paths are always closed (automatically by the program if not manually by the user) before a Boolean operation is performed.

But are they actually closed before the operation is performed or is it just that the boolean math considers only the areas enclosed by the paths & enclose those areas with closed paths after the math is done? IOW, if the History panel broke these operations out into separate steps, would we see the close step(s) before or after the math step?

 

Right now that distinction doesn't matter (except possibly for identifying & eliminating any bugs associated with the boolean operations), but it might matter in the future if a scripting language was added, if the History panel was reworked to show more 'internal' detail, etc.

 

Regardless, it is just my opinion but I think it is best to avoid saying anything that suggests or implies the booleans only work on closed areas because that is not true no matter how it works internally.

[Alfred]

28 minutes ago, R C-R said:

But are they actually closed before the operation is performed or is it just that the boolean math considers only the areas enclosed by the paths & enclose those areas with closed paths after the math is done?

 

To answer that, try a ‘Divide’ (or whatever) followed by ‘Undo’.

[R C-R]

1 hour ago, Alfred said:

To answer that, try a ‘Divide’ (or whatever) followed by ‘Undo’.

That just returns the document to the step before the boolean was performed, making open paths that were closed open again, so I am not sure what I should deduce from that.

[Alfred]

4 hours ago, R C-R said:

That just returns the document to the step before the boolean was performed, making open paths that were closed open again, so I am not sure what I should deduce from that.

 

I’m not sure now, either!  I guess I was thinking that if it worked like Alt-dragging to create a duplicate there would be a separate ‘Close all selected curves’ step in the History (so that a single ‘Undo’ would leave the curve closed).