I'm trying to come up with the simplest way to create a polyline within a closed polyline. For example, suppose I draw a rectangle 1 unit wide and two units tall. This sits on a frustum (truncated triangle) one unit wide at the top and 3 units wide at the base. I need to draw a line (polyline) down the center of the rectangle (therefore offset from the left of the rectangle by 1/2 unit), starting 1/2 unit inset from the top of the rectangle. This line must then follow the contour of the frustum inset by the same amount (1/2 unit). What I must end up with is a single line sitting on top of a triangle, the single line starting 1/2 unit down from the top of the rectangle, running down the center of the rectangle, then running into a triangle, the outline of which is 1/2 unit inside the contour of the frustum. This would be a very simple example to do manually, but I have to be able to do it on a complex closed polyline which is composed primarily of curves. If you imagine a letter drawn in calligraphy, I need to draw a single line down the center of the narrowest portions, where the width of that portion is X. Where the width becomes greater than X I must have a polyline inside the figure offset (inside the figure) by 1/2(X).
I hope that's clear enough of an explanation.
I'm looking for all solutions, including any AUOTLISP functions someone may have or could come up with. Thanks. (This has also been posted in the General Forum.)