[Solved] Sector of concentric circles

[DavidHMcCracken]

How can I create a sector of concentric circles in Draw? The image that I'm trying to create is of a wave emerging from an aperture, in order to illustrate interference (typically of light but in my case of electron position probability). Concentric hemispheres are easily created in both Draw and Impress by using the Arc-Circle tool with snap to 270 and 90 degrees and then duplicate. But this works only because the duplication parameters are linear. They are not when I'm trying to make a sector of the same basic image. The Modify > Shapes > Subtract function doesn't treat a group as one object so I can't subtract a rectangle over a group of concentric circles.

[Zizi64]

The Modify > Shapes > Subtract function doesn't treat a group as one object so I can't subtract a rectangle over a group of concentric circles.

I agree: it not work with more than one standalone circles.
But the SUBSTRACT and rhe INTERSECT functions work in my LibreOffice 5.4.6 version, when the circles are GROUPED really (you can groping them with the "Group" function)

Grouped circles.odg

(12.8 KiB) Downloaded 235 times

[DavidHMcCracken]

Thank you Zizi64 for your suggestion but I tried LO 5.4.6.2 (64) on Windows 10 and got the same result as for AOO 4.1.5 on Ubuntu-Mate 16.04. Perhaps I am not doing it correctly. I first make my concentric circles. I combine them into one group using Modify > Group. To confirm grouping, I grab one of the circles; the entire group is obviously selected and I drag the group around a bit to be sure. I then draw one rectangle (hollow or filled makes no difference) on top of the group, occluding a portion of each circle. I select all (that is the rectangle and the group of circles). Modify > Shapes > Subtract removes the occluded portion of the largest circle, as expected, but it completely removes all of the other circles. Whether the circles are created from largest to smallest or vice versa makes no difference. To select all I have tried both simply selecting all and selecting first the group and then shift-select to add the rectangle. In all cases, only the unoccluded portion of the largest circle remains after Subtract.

[Zizi64]

Please upload your ODF type sample file (with the state "before the substraction").

[DavidHMcCracken]

These were produced under LO 5.4.6.2.

beforeSubtract.odg

(11.21 KiB) Downloaded 238 times

afterSubtract.odg

(8.1 KiB) Downloaded 235 times

[Zizi64]

Try to use non-zero line width for the circles, and a filled shape to the rectangle...

[DavidHMcCracken]

Many thanks to Zizi64 for responding so quickly and solving my problem. Using 0-width circle lines is the solution. It works in both LO and AOO. In LO I tried this without filling the rectangle and only the bits of circles under the rectangle border were erased. I repeated with the rectangle filled and everything under the rectangle was erased. I repeated the experiments in AOO and found that the 0-width circle lines was the complete solution and whether the rectangle was filled made no difference. I tried again in LO and found that filling the rectangle made no difference. So I'm not sure about filling the rectangle but it is easy to do.

Further manipulation of the resulting figure reveals the root of my problem. I wanted 0-width lines because they render better in my slides, no doubt because they afford the rendering engine more optimizing freedom. But I was not able to change their width in the final figure or any other aspect, e.g. line color, group/ungroup, etc. The resulting figure is obviously no longer a group of circle/sectors but a hard-wired image. The subtractor was confused by the abstract 0-width lines because it wants to work on and produce images.