Hi Brian, I think the fin method is equivalent to a "radial projection", but a radial type projection probably isn't what you really want. With a radial projection things that are further away from the radial axis are traversing a longer distance than things close to the radial axis, and so on a shape like your rounded rectangle that is not symmetrical around the axis and has some portions further away and some closer to the radial axis it will yield that curved result that you don't want.

Flow is probably more what you want, since that can map an elevation onto a path just based on distance traveled along the path.

- Michael