Trim A

The current drawing actually contains all of the outer boundaries we need, but it has some extra lines too. What we need to do is trim off the extra lines. One way to do this is with the "Break Polygons" function. This function looks at a set of boundary polygons and a set of polygons to trim, and cuts every polygon to trim where it is crossed by a boundary polygon. Points may also be used as boundaries. Start the breakPolygons function found as "Break Polygons" under "Polygon Constructions". This function's input dialog has two fields. The first is an object set field used to input the polygons to trim. When this field is highlighted, select all of the lines of the A. To move to the next field either you can hit OK, or you can hit the right mouse button in the viewport, or you can touch the next field with the mouse. The next field is also an object set type, used to input the trimming boundaries. Select all of the lines again, and hit OK (or right click in the viewport). The result is lots of small lines. Now you only need to delete all of the lines that are unwanted.

Notice that the remaining lines form two closed loops. We don't want all of these independent lines. It is better to join the small lines together into two closed polygons using the joinPolygons function , found as "Join Polygons" under "Polygon Constructions". Start the function and pick all the the lines (in any order) of the outer contour and hit OK. Then do the same for the three lines in the inner contour. We now have two objects instead of 20 or so.
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