1. A method for determining shear information with ultrasound, the method comprising: estimating first shear information at sparse locations of a grid; calculating second shear information for a more dense sampling of the grid, the more dense sampling being a sampling of a greater number of additional locations of the grid than a number of the sparse locations, the calculating of the second shear information being a function of the first shear information; and displaying an image as a function of the second shear information; wherein calculating the second shear information comprises calculating first stress at the sparse locations as a function of the first shear information, calculating diffusion of the first stress for the more dense sampling grid, and calculating the second shear information as a function of the diffusion.