WrapMap

The motivation for the first version of WrapMap was indeed to generate rims for bumpmaps.

There is a neat trick you can use to generate a really complex rim with little effort:

1. In the bitmap layer, draw a black-to-white gradient
2. Open the colors curves tool on that layer, and use it to define you rim section graphically:

   

   This will produce something like:

   

3. Apply Wrapmap on your selection to produce the bumpmap:

   

4. And run the bumpmap filter: