Hi Peter, curve booleans will focus on forming closed loops.
In the case you've got there, your pieces are overlapping in enough areas to create several closed loops, like here are 2 of them:
The booleans don't know to give any special importance to one closed loop over another, so you will get them all - the above result was from boolean union applied to the curves.
If you want a different result than this, you can use Edit/Trim to gain more exact control over what pieces to remove.
Here is the procedure to use Trim - first select all the pieces:
Then run Edit/Trim. In the upper-right area of the screen it will display a prompt for "Select cutting objects or Done for mutual trim".
In this case you don't need to select any other cutting objects, you want all pieces to both be cut and to cut the others. So for this stage you don't pick anything and just push Done (or right-click in the viewport).
That will then cut all the pieces up and the various fragments will be displayed, it should look like this:
Now you can select which pieces you want to remove. In this case you want to pick the inside pieces (if I understand your goal correctly).
It can help to do window selects to pick several pieces in one action. Like in this case you can grab everything by one strategic window starting in the upper-right corner and dragging down to the lower left, like this:
You can also just click individually on the pieces you want to discard, and you can also switch the Mode: option to Mode: Keep and click on the pieces you want to keep instead of the pieces you want to discard.
After you are done picking the pieces to discard, push "Done" or right-click and this will be the result:
Now you can select those pieces and use Edit/Join to glue them into a single curve if you want.
If your curves have a lot of criss-crossing areas, you will need to do this kind of trim operation to cut away the specific pieces that you want.
I hope this helps, and please let me know if you have any problems following these steps!
- Michael
