PixelPerfect #17: Displacement
It might take Einstein to help explain the complex physics of bending light, but when it comes to bending pixels, it is an art commonly referred to in Photoshop as displacement. Displacement can let you use the lumonosity values of one image to bend the pixels of another; a "relativity" of sorts. No offense to Einstein, but Bert can explain this one on his own.
Bert has made his source files available for this episode available here