Trim without surface

region union cannot work if regions aren’t planar:

also no need to duplicate the thread:

make sure shapes are planar, or at least project:

however, keep in mind, with this geometry you can simply get a cross section of the bounding boxes with the plane, without region union, resulting in the same rectangles:

hope it helps

check the attachment
regionunionnotworking.gh (10.9 KB)

1 Like