update Jan 14,2020: Xcode 11.3.1, Swift 5
realtime FFT of audio input, for iPad using Swift and Metal
Based on FFT and Audio Input code written by John Scalo
https://github.com/jscalo/tempi-fft
Realtime audio input is run through an FFT, and the data is cycled
through a 3D terrain as height map slices.
Makes for an interesting display of your singing voice.
