1. A method of measuring three-dimensional motion of an object by harmonic phase magnetic resonance imaging comprising applying a first tag pulse sequence to spatially modulate a region of said object within the short axis plane, acquiring a first spectral peak from the Fourier domain of said spatially modulated object, computing the inverse Fourier transform information of said acquired first spectral peak, computing a first harmonic phase image, applying a second tag pulse sequence to spatially modulate a region of interest of said object in a direction perpendicular to said first tag pulse sequence within the short axis plane, acquiring a second spectral peak from the Fourier domain of said spatially modulated object, computing the inverse Fourier transform information of said acquired second spectral peak, computing a second harmonic phase image, creating tagged images of circumferential and radial strains by combining said first harmonic phase image and said second harmonic phase image, applying a third tag pulse sequence in a third direction generally perpendicular to said first and second tag pulse sequences through said region of interest of said object, and creating a third harmonic phase image therefrom, applying a fourth tag pulse sequence of a different strength than said third tag pulse sequence in a fourth direction generally perpendicular to said first and second tag sequences and generally in said third direction and creating a fourth harmonic phase image therefrom, and determining longitudinal strain by combining said third and fourth harmonic phase images to determine strain in the longitudinal direction.