Reflections are easy geometric transformations. I think in this case it's about inverse geometry, which is much more difficult to perform https://en.wikipedia.o

Reflections are easy geometric transformations. I think in this case it's about inverse geometry, which is much more difficult to perform https://en.wikipedia.org/wiki/Inversive_geometry https://en.wikipedia.org/wiki/Inversive_geometry EDIT : another comment here suggest it's even more complex, using Laplacian