Realistic fold of sheet material?

There is a YouTube video titled:

rhinoceros sheet metal grasshopper 3d experiment

Most interested in the bend shown and need pointers on how to construct such a fold. (Slicing, Splitting and Rotating parts of forms developed from modeled sheet material doesn’t look very realistic!) Is this a rolling ball transition between two sheet parts? What Grasshopper functions should I study in order to control angle of fold?

You can create something like that (14.5 KB)


MUCH more helpful than I expected!
Appreciated and Thank You