When I was a kid I learned how to edit images using sumopaint. It used to have this layer effect called "gradient bevel" which created a very interesting effect where the gradient would warp depending on the shape of the objects with consideration for alpha.
I currently use Gimp for image editing, and it appears to not have this as an option. "gradient map" only converts existing colors into colors along a selected gradient depending on their value, and "bevel" creates a sharp bevel effect which I'm not interested in using.
Would anyone happen to know if there is a plugin that would create this effect in Gimp, or if there is any way to manually achieve this effect?