VisualizeMultiShellScheme
=========================

.. code-block:: none

  % visualize single or multiple shell schemes
  %
  % USAGE:
  %   VisualizeMultiShellScheme(grad1)
  %   VisualizeMultiShellScheme(grad1, grad2, grad3)
  %
  % INPUT
  %   varargin :  One or more matrix for schemes in different shells. 
  %               Each matrix has size N_ix3, N_i is the number of samples in the i-th shell.
  %
  % Copyright (c) 2014, Jian Cheng <jian.cheng.1983@gmail.com>
  %