Thank you very much. It works !!!Circle or not - create a power copy. Fill each "circle" with Fill operation. Then plant a "Point on Surface" with the coordinates 0 - they should land more or less in the center of the circle as the circles appear to be very irregular. Then connect the points. If the spline becomes very twisted you can reduce the number of points.
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This is a very elegant approach but I can't understand what does the "centerofgravity()" formula result in? Where do you put that formula? Do I need to pull out the X, Y and Z coordinates from the center of gravity formula accordingly? Can you put more screenshots? Thanks.